研究者データベース

仲岡 雅裕(ナカオカ マサヒロ)
北方生物圏フィールド科学センター 水圏ステーション 厚岸臨海実験所
教授

基本情報

所属

  • 北方生物圏フィールド科学センター 水圏ステーション 厚岸臨海実験所

職名

  • 教授

学位

  • 博士(理学)(東京大学)

ホームページURL

科研費研究者番号

  • 90260520

ORCID ID

J-Global ID

プロフィール

  • Masahiro (Massa) Nakaoka is a professor of Hokkaido University and the director of Akkeshi Marine Station, Field Science Center for Northern Biosphere, Hokkaido University where he has been working for since 2008.


    Massa completed his Ph.D and undergraduate studies at University of Tokyo. His research interests lie in the area of marine ecology, ranging from basic subjects like plant-animal interactions in eelgrass beds, to more applied ones like evaluation of multiple ecosystem services from coastal ecosystems in Asia. He has collaborating activity with researchers in other countries, using Akkeshi Marine Station as a node of international network studies including ZEN (Zostera Experimental Network), GAME (Global approach by Modular Experiments) and TSUNAGARI (Belmont Forum-funded international project).


    Massa has served on committees on international and Japanese academic societies and journals such as Steering Committee of World Seagrass Association (2012-present), Editor-in-Chief of Ecological Research (Springer) and an Associate Editor of Estuaries and Coasts (Springer).

研究キーワード

  • 沿岸生態系   海草   生態系機能   生物群集   生物多様性   海草藻場   アマモ場   生態学   岩礁潮間帯   ベントス   藻場   空間スケール   群集動態   生物間相互作用   メタ個体群   野外操作実験   物質循環   群集   広域分散過程   リモートセンシング・GIS   食物網   炭素吸収能   空間異質性   種間関係   

研究分野

  • ライフサイエンス / 生態学、環境学
  • 環境・農学 / 環境動態解析
  • ライフサイエンス / 生態学、環境学
  • 環境・農学 / 生物資源保全学

職歴

  • 2008年04月 - 現在 北海道大学 北方生物圏フィールド科学センター 教授
  • 2001年10月 千葉大学 大学院理学研究科 准教授
  • 1993年04月 - 2001年09月 東京大学 海洋研究所 助手

所属学協会

  • World Seagrass Association   日本地球惑星科学連合   個体群生態学会   日本ベントス学会   日本生態学会   

研究活動情報

論文

  • J. Emmett Duffy, John J. Stachowicz, Pamela L. Reynolds, Kevin A. Hovel, Marlene Jahnke, Erik E. Sotka, Christoffer Boström, Katharyn E. Boyer, Mathieu Cusson, Johan Eklöf, Aschwin H. Engelen, Britas Klemens Eriksson, F. Joel Fodrie, John N. Griffin, Clara M. Hereu, Masakazu Hori, A. Randall Hughes, Mikhail V. Ivanov, Pablo Jorgensen, Claudia Kruschel, Kun-Seop Lee, Jonathan S. Lefcheck, Per-Olav Moksnes, Masahiro Nakaoka, Mary I. O’Connor, Nessa E. O’Connor, Robert J. Orth, Bradley J. Peterson, Henning Reiss, Katrin Reiss, J. Paul Richardson, Francesca Rossi, Jennifer L. Ruesink, Stewart T. Schultz, Jonas Thormar, Fiona Tomas, Richard Unsworth, Erin Voigt, Matthew A. Whalen, Shelby L. Ziegler, Jeanine L. Olsen
    Proceedings of the National Academy of Sciences 119 32 2022年08月09日 
    Distribution of Earth’s biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate–trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth’s environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass ( Zostera marina ), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.
  • Collin P. Gross, J. Emmett Duffy, Kevin A. Hovel, Melissa R. Kardish, Pamela L. Reynolds, Christoffer Boström, Katharyn E. Boyer, Mathieu Cusson, Johan Eklöf, Aschwin H. Engelen, Britas Klemens Eriksson, F. Joel Fodrie, John N. Griffin, Clara M. Hereu, Masakazu Hori, A. Randall Hughes, Mikhail V. Ivanov, Pablo Jorgensen, Claudia Kruschel, Kun-Seop Lee, Jonathan Lefcheck, Karen McGlathery, Per-Olav Moksnes, Masahiro Nakaoka, Mary I. O'Connor, Nessa E. O'Connor, Jeanine L. Olsen, Robert J. Orth, Bradley J. Peterson, Henning Reiss, Francesca Rossi, Jennifer Ruesink, Erik E. Sotka, Jonas Thormar, Fiona Tomas, Richard Unsworth, Erin P. Voigt, Matthew A. Whalen, Shelby L. Ziegler, John J. Stachowicz
    Proceedings of the Royal Society B: Biological Sciences 289 1969 2022年02月23日 
    While considerable evidence exists of biogeographic patterns in the intensity of species interactions, the influence of these patterns on variation in community structure is less clear. Studying how the distributions of traits in communities vary along global gradients can inform how variation in interactions and other factors contribute to the process of community assembly. Using a model selection approach on measures of trait dispersion in crustaceans associated with eelgrass ( Zostera marina ) spanning 30° of latitude in two oceans, we found that dispersion strongly increased with increasing predation and decreasing latitude. Ocean and epiphyte load appeared as secondary predictors; Pacific communities were more overdispersed while Atlantic communities were more clustered, and increasing epiphytes were associated with increased clustering. By examining how species interactions and environmental filters influence community structure across biogeographic regions, we demonstrate how both latitudinal variation in species interactions and historical contingency shape these responses. Community trait distributions have implications for ecosystem stability and functioning, and integrating large-scale observations of environmental filters, species interactions and traits can help us predict how communities may respond to environmental change.
  • Ken Ishida, Michikusa Tachibana, Masakazu Hori, Takehiro Okuda, Tomoko Yamamoto, Masahiro Nakaoka, Takashi Noda
    Scientific Reports 11 1 2021年12月 
    AbstractLong-term patterns in trajectories of natural communities provide insights into ecological resilience, but their assessment requires long-term census data. We analyzed 16-year census data for intertidal communities from 30 rocky shores along Japan’s Pacific coast to assign community change to four possible trajectories (stable, reversible, abrupt, or linear) representing different aspects of ecological resilience, and to estimate multiple metrics of temporal invariability (species richness, species composition, and community abundance). We examined (1) how the prevalence of the four trajectories differs among regions, (2) how the features (model coefficients) of each trajectory vary among regions, and (3) how the temporal invariabilities differ among trajectories and regions. We found that the stable trajectory was the most common. Its features differed among regions, with a faster recovery to steady-state equilibrium in low-latitude regions. Furthermore, trajectories and temporal invariabilities both varied among regions, seemingly in association with the strength of ocean current fluctuations. Thus, the relationship between community temporal invariability and trajectory may be weak or absent, at least at the regional scale.
  • Tomonori Isada, Hiroya Abe, Hiromi Kasai, Masahiro Nakaoka
    Frontiers in Marine Science 8 2021年10月11日 [査読有り]
     
    Coastal oceans interacting with terrestrial ecosystems play an important role in biogeochemical cycles. It is therefore essential to research land–ocean interactions for further understanding of the processes influencing nutrients dynamics in coastal areas. We investigated the seasonal and spatial distribution of nutrient concentrations and light absorption coefficients of colored dissolved organic matter (CDOM), non-algal particles (NAP), and phytoplankton in a wetland-influenced river–eelgrass meadows–coastal waters continuum in the protected and semi-enclosed coastal sea of Akkeshi-ko estuary (AKE) and Akkeshi Bay (AB), Japan from April 2014 to February 2015. The mixing dilution lines of the CDOM absorption coefficient at 355 nm [aCDOM(355)] relative to salinity predicted by two end-members between freshwater and coastal water showed conservative mixing in AB. Silicate concentrations were significantly correlated with salinity and aCDOM(355) in AB in each month except for December 2014. These results suggest that silicate and CDOM in AB primarily originates from wetland-influenced river discharge. However, samples collected from the eelgrass meadows of AKE, where mariculture is developed, showed non-conservative mixing of silicate concentrations and aCDOM(355) with salinity except for June 2014. Elevated phosphate concentrations, probably released from sediments, were also found in the eelgrass meadows of AKE, especially during summer. These results suggest that the metabolic activities of mariculture and seagrass ecosystem significantly contribute to the nutrient cycles and CDOM absorption in AKE and to the distinct water-mass systems inside and outside AKE. The relative absorption properties of NAP [aNAP(443)], phytoplankton [aph(443)], and aCDOM(443) showed that CDOM is the main factor affecting the light distribution in AKE. However, the relative absorption properties varied seasonally in AB because of spring and autumn phytoplankton blooms and ice cover during winter. Significant relationships were observed between the Secchi disk depth (ZSD), aNAP(443), and aCDOM(443). Chl a concentration and aph(443) were not good indicators for predicting ZSD in our study region. These results suggest that incorporating inherent optical properties and CDOM from mariculture and seagrass ecosystem into ecosystem models could improve predictions of light distribution along the freshwater–eelgrass–coastal waters continuum in optically complex coastal waters.
  • MA Ito, HJ Lin, MI O’Connor, M Nakaoka
    Marine Ecology Progress Series 675 1 - 21 2021年09月30日 [査読有り]
     
    Large-scale analysis along latitude or temperature gradients can be an effective method for exploring the potential roles of light and temperature in controlling seagrass phenology. In this study, we investigated effects of latitude and temperature on seagrass biomass and reproductive seasonality. Zostera japonica is an intertidal seagrass with a wide latitudinal distribution expanding from tropical to temperate zones in its native range in Asia, with an additional non-native distribution in North America. We collated available data on phenological traits (timings of peak biomass or reproduction, durations of biomass growth and reproductive season, and maximum biomass or reproductive ratio) from publications and our own observations. Traits were compared among geographic groups: Asia-tropical, Asia-temperate, and North America-temperate. We further examined relationships between traits and latitude and temperature for 3 population groups: Asian, North American, and all populations. Our analysis revealed significant variation among geographic groups in maximum biomass, peak reproductive timing, and maximum reproductive ratio, but not in other traits. Maximum biomass and peak reproductive timing for Asian and all populations were significantly correlated with latitude and temperature. Maximum biomass was highest at mid-latitudes or intermediate temperatures and decreased toward distribution range limits, and peak reproductive timing occurred later in the year at higher latitudes or cooler sites. North American populations showed shorter growth durations and greater reproductive ratios at higher latitude. Different responses observed for North American populations may reflect effects of introduction. Our study demonstrates potential variation among geographic regions and between native and non-native populations.
  • Kazuki Miura, Nobuo Ishiyama, Junjiro N. Negishi, Daisetsu Ito, Keita Kawajiri, Hokuto Izumi, Takahiro Inoue, Masahiro Nakaoka, Futoshi Nakamura
    2021年09月23日 
    AbstractMultiple stressors can interactively affect the population of organisms; however, the process by which they affect recruitment efficiency remains unclear for empirical populations. Recruitment efficiency can be regulated at multiple stages of life, particularly in organisms with complex life cycles. Understanding the interactive effects of multiple stressors on recruitment efficiency and determining the bottleneck life stages is imperative for species conservation. The proportion of <20-year-old juveniles of the endangered freshwater pearl mussel Margaritifera togakushiensis, which has an obligate parasitic larval stage, was investigated in 24 rivers from eastern Hokkaido, northern Japan to reveal the influence of nutrients, fine sediment, and their combined effects on juvenile recruitment efficiency. The following indices for recruitment at adult, parasitic, and post-parasitic juvenile stages were obtained from 11 of these rivers: gravid female density, glochidia density (the number of glochidia infections per stream area), and juvenile survival rate. This study explored the bottleneck stages of recruitment efficiency and the interactive effects of the two stressors on these stages. Twenty-four population status assessments determined that the proportion of juveniles ranged from 0.00 to 0.53, and juveniles were absent from four rivers. The results showed that the parasitic and post-parasitic juvenile stages were bottlenecks for recruitment efficiency. Juvenile survival rates had a more significant positive effect on recruitment efficiency in rivers with a high glochidia density. Juvenile survival rate was decreased by the synergistic interaction of nutrients and fine sediment, although factors limiting glochidia density were not found. The nutrient concentration of rivers in the study region was well explained by the proportion of agricultural land cover and urban areas in the watersheds, but no relationship was detected between fine sediment abundance and land use. This study suggests that nutrient management at a catchment scale can be effective for re-establishing the recruitment of M. togakushiensis, particularly in rivers with a high content of fine sediments. The results also emphasise the importance of considering both parasitic and post-parasitic juvenile stages of mussels to maximise the positive effects of stressor mitigation.
  • T. E. Angela L. Quiros, Kenji Sudo, Reynante V. Ramilo, Helbert G. Garay, Muammar Princess G. Soniega, Alvin Baloloy, Ariel Blanco, Ayin Tamondong, Kazuo Nadaoka, Masahiro Nakaoka
    Frontiers in Marine Science 8 2021年08月03日 [査読有り]
     
    Ecosystem services (ES) are benefits nature provides to humans; these services change in space and time and are largely dependent on context. Coastal habitat that provides key ES are blue carbon ecosystems, namely seagrass and mangroves. One important ES they provide is the provisioning of seafood, which benefits coastal populations with livelihoods and food security. We employed a social-ecological approach that draws from the vulnerability literature for social, ecological, and economic criteria to map ES provision in ten communities on Busuanga Island, Palawan Province, Philippines. We assess the spatial dynamics of ES provision for small-scale fisheries in seagrass and mangroves, in relation to local beneficiaries. Using a mixed-methods approach with ecological assessments of seagrass beds, spatial analysis, landing surveys, household and key informant interviews, we overlaid biophysical variables on social data, mapping sensitivities and adaptive capacities to compare communities’ social vulnerabilities. Spatial analysis revealed healthy blue carbon ecosystems in ten local communities (barangays) as measured by proportion of coastline covered, low patchiness and high continuity along the coastline, and the presence of adjacent habitat. We found seagrass ecosystems were more vulnerable than mangroves. Rural barangays had less exposure and lower sensitivity to blue carbon ecosystem loss than urban barangays. Blue carbon ecosystem fisheries are highly sensitive fisheries, due to their catch composition and low catch per unit effort, with mangrove fisheries having a slightly lower sensitivity than seagrass fisheries due to greater catch per unit effort. Diversified livelihoods and the presence of NGOs and People’s Organizations (POs) increased adaptive capacity and reduced overall vulnerability. We aim to highlight a coastal human community’s relationship with blue carbon ecosystems using context-specific vulnerability criteria. Our site-specific social vulnerability assessment may be adapted for use in other coastal communities within the coral triangle. This work suggests opportunities for conservation interventions to manage local communities’ sensitivities and adaptive capacity around the use of blue carbon ecosystems.
  • Kenji Sudo, T. E. Angela L. Quiros, Anchana Prathep, Cao Van Luong, Hsing-Juh Lin, Japar Sidik Bujang, Jillian Lean Sim Ooi, Miguel D. Fortes, Muta Harah Zakaria, Siti Maryam Yaakub, Yi Mei Tan, Xiaoping Huang, Masahiro Nakaoka
    Frontiers in Marine Science 8 2021年07月08日 [査読有り]
     
    Although Southeast Asia is a hotspot of global seagrass diversity, there are considerable information gaps in the distribution of seagrass beds. Broad-scale seagrass distribution has not been updated in the global seagrass database by UNEP-WCMC since 2000, although studies on seagrasses have been undertaken intensively in each region. Here we analyze the recent distribution of tropical seagrass beds, their temporal changes, causes of decline and conservation status in Southeast Asia (plus southern mainland China, Taiwan and Ryukyu Island of Japan) using data collected after 2000. Based on the 195 literature published since 2000, we identified 1,259 point data and 1,461 polygon data showing the distribution of seagrass beds. A large discrepancy was found in the seagrass bed distribution between our updated data and the UNEP-WCMC database, mostly due to inaccurate and low resolution location information in the latter. Temporal changes in seagrass bed area analyzed for 68 sites in nine countries/regions demonstrated that more than 60% of seagrass beds declined at an average rate of 10.9% year–1, whereas 20% of beds increased at an average rate of 8.1% year–1, leading to an overall average decline of 4.7% year–1. Various types of human-induced threats were reported as causes for the decline, including coastal development, fisheries/aquaculture, and natural factors such as typhoons and tsunamis. The percentage of seagrass beds covered with existing marine protected areas (MPAs) varied greatly among countries/regions, from less than 1% in Brunei Darussalam and Singapore to 100% in southern Japan. However, the degree of conservation regulation was not sufficient even in regions with higher MPA coverage. The percentage of seagrass beds within EBSAs (Ecologically and Biologically Significant Area determined by the Convention of Biological Diversity) was higher than that within MPAs because EBSAs cover a greater area than MPAs. Therefore, designating EBSAs as legally effective MPAs can greatly improve the conservation status of seagrass beds in Southeast Asia.
  • 但馬英知・法理樹里・小林由美・牧野光琢・仲岡雅裕 (2021) 社会・環境変動に関する住民意識調査に基づく地域将来シナリオの検討‐北海道・厚岸を事例に
    但馬英知, 法理樹里, 小林由美, 牧野光琢, 仲岡雅裕
    沿岸域学会誌 34 37 - 46 2021年06月 [査読有り]
  • Kevin A. Hovel, J. Emmett Duffy, John J. Stachowicz, Pamela Reynolds, Christoffer Boström, Katharyn E. Boyer, Stéphanie Cimon, Mathieu Cusson, Fredrick Joel Fodrie, Karine Gagnon, Clara M. Hereu, Masakazu Hori, Pablo Jorgensen, Claudia Kruschel, Kun‐Seop Lee, Masahiro Nakaoka, Nessa E. O’Connor, Francesca Rossi, Jennifer Ruesink, Fiona Tomas, Shelby Ziegler
    Ecology 102 5 2021年05月 [査読有り]
  • Kazuma Gomi, Yohei Nakamura, Masaru Kanda, Kentaro Honda, Masahiro Nakaoka, Chiho Honma, Masao Adachi
    Journal of Fish Biology 2021年03月07日 [査読有り]
     
    The feeding ecology of scarinine parrotfishes on tropical coral reefs has received considerable attention in the past few decades; however, relatively few studies have been conducted in high-latitude reefs. Among the Indo-Pacific Scarus species, Scarus ovifrons is unique, being largely restricted to the warm temperate waters of Japan. However, there is very little information available on the feeding ecology of this species. In this study, we used acoustic telemetry to detect the diel vertical movement patterns of S. ovifrons, video survey to detect its feeding depths and substrata and focal follow survey and genetic analysis to identify algae composition on the feeding scars at Kashiwajima Island, southwestern Japan (32°46'N, 132°38'E). Acoustic telemetry revealed that S. ovifrons spent most of its time in shallow water (<10 m) during the day and slept in deeper water (10-15 m) at night. Video and focal follow surveys revealed that most fishes of various sizes regularly took bites on epilithic algae and detrital materials on rocky substrata at depths of <10 m, but large fishes (>40 cm total length) sometimes took bites directly on live corals (Acropora solitaryensis) at the 5 m depth zone where live tabular corals dominated the benthos. Molecular phylogenetic analyses revealed that epilithic algae collected from feeding scars were mainly composed of Rhodophyta, and coralline algae were less often targeted. Overall, this study revealed that S. ovifrons feeds mostly at depths <10 m and the feeding algae substrata of the species are similar to those of tropical coral reef parrotfishes. This article is protected by copyright. All rights reserved.
  • Yayoi Takeuchi, Hiroyuki Muraoka, Takehisa Yamakita, Yuichi Kano, Shin Nagai, Touch Bunthang, Mark John Costello, Dedy Darnaedi, Bibian Diway, Tonny Ganyai, Chaiwut Grudpan, Alice Hughes, Reiichiro Ishii, Po Teen Lim, Keping Ma, Aidy M. Muslim, Shin‐ichi Nakano, Masahiro Nakaoka, Tohru Nakashizuka, Manabu Onuma, Chan‐Ho Park, Runi Sylvester Pungga, Yusuke Saito, Mangal Man Shakya, Mohd Khairulazman Sulaiman, Maya Sumi, Phanara Thach, Yongyut Trisurat, Xuehong Xu, Hiroya Yamano, Tze Leong Yao, Eun‐Shik Kim, Sheila Vergara, Tetsukazu Yahara
    Ecological Research 36 2 232 - 257 2021年03月 [査読有り]
     
    The Asia-Pacific Biodiversity Observation Network (APBON) was launched in 2009, in response to the establishment of the Biodiversity Observation Network under the Group on Earth Observations in 2008. APBON's mission is to increase exchange of knowledge and know-how between institutions and researchers concerning biodiversity science research in the Asia-Pacific (AP) region and thereby contribute to evidence-based decision-making and policy-making. Here we summarize APBON activities and achievements in its first 10 years. We review how APBON has developed networks, facilitated communication for sharing knowledge, and built capacity of researchers and stakeholders through workshops and publications as well as discuss the network plan. Key findings by APBON members include descriptions of species new to science, mapping tropical forest cover change, evaluating impacts of hydropower dams and climate change on fish species diversity in the Mekong, and mapping "Ecologically and Biologically Significant Areas" in the oceans. APBON has also contributed to data collection, sharing, analysis, and synthesis for regional and global biodiversity assessment. A highlight was contributing to the "Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services" regional report. New strategic plans target the development of national-level BONs and interdisciplinary research to address the data and knowledge gaps and increase data accessibility for users and for meeting societal demands. Strengthening networks in AP region and capacity building through APBON meetings will continue. By promoting monitoring and scientific research and facilitating the dialogue with scientists and policymakers, APBON will contribute to the implementation of conservation and sustainable use of biodiversity in the entire AP region.
  • Takaaki Hasegawa, Masahiro Nakaoka
    Environmental Pollution 273 116468 - 116468 2021年03月 [査読有り]
  • Masaya Yoshikai, Takashi Nakamura, Yoshiyuki Tanaka, Masahiro Nakaoka, Atsushi Watanabe, Eugene C. Herrera, Takumi Tsuchiya, Toshihiro Miyajima, Maria Lourdes San Diego-McGlone, Miguel D. Fortes, Ariel C. Blanco, Ayin M. Tamondong, Kazuo Nadaoka
    Estuarine, Coastal and Shelf Science 250 107152 - 107152 2021年03月 [査読有り]
     
    © 2020 Elsevier Ltd This study assessed the estuarine-scale dynamics of mixed seagrass beds in Bolinao and Anda coastal areas in the Philippines, where seagrass beds have declined primarily due to eutrophication-induced degradation of light environment caused by unregulated mariculture activities in the adjacent areas. A seagrass model, driven by a coupled hydrodynamic-biogeochemical model, was developed and applied to the two-dominant species in the area – Thalassia hemprichii and Enhalus acoroides, and validated using observed spatial seagrass shoot density. The results showed the degradation of light environment in the seagrass beds, especially near mariculture areas, due to advective fluxes of water with high phytoplankton biomass and high nutrients from fish farms. The seagrass model driven by the reproduced water quality showed high reproducibility of seagrass above-ground biomass distribution of the two co-existing species, with R2 values of 0.78 and 0.60 for T. hemprichii and E. acoroides, respectively. Scenario analysis was conducted to examine the effectiveness of individual- and inter-municipality mariculture management (e.g., regulating fish feed input) in improving the light environment and facilitating the recovery of seagrasses. Results showed that the light environment could be significantly enhanced by an inter-municipality scheme compared to individual efforts of Bolinao and Anda municipalities, since their waters are interconnected through hydrodynamics. In conjunction with the improvement of light conditions, the recovery in seagrass abundance is most significant under the cooperative management scheme, thus highlighting its effectiveness.
  • Hisatomo Waga, Toru Hirawake, Masahiro Nakaoka
    Polar Science 27 100554 - 100554 2021年03月 [査読有り]
     
    The substantial loss of Arctic sea ice will alter marine ecosystems in many ways. Recent studies have reported a distributional shift in benthic macrofaunal biomass in the Pacific Arctic, likely caused by changes in food availability for benthic organisms. Here, we assessed the influence of differences in post-bloom supply of phytoplankton to the sediment on the growth of a common Pacific Arctic bivalve (Macoma calcarea) based on field and satellite observations, and feeding experiments. Among the sampling stations examined, the spatial distribution of M. calcarea body size showed clear variations and was associated with phytoplankton size structure during the post-bloom period. In addition, our feeding experiment exposing M. calcarea to different feeding treatments suggest that the continuous settlement of fresh phytoplankton is more important for the bivalve?s growth than the total amount of phytoplankton settlement. This could explain the significant linkage between M. calcarea body size and phytoplankton size structure during the post-bloom period, because the larger phytoplankton represent an influx of fresh phytoplankton to the sediment and hereby support better growth and/ or longevity of bivalves. Our study provides novel insights into a variety of processes related to the growth of M. calcarea and its relationship with the phytoplankton community.
  • Guido Bonthond, Till Bayer, Stacy A. Krueger-Hadfield, Nadja Stärck, Gaoge Wang, Masahiro Nakaoka, Sven Künzel, Florian Weinberger
    The ISME Journal 2021年01月21日 [査読有り]
     
    AbstractInvasive species are co-introduced with microbiota from their native range and also interact with microbiota found in the novel environment to which they are introduced. Host flexibility toward microbiota, or host promiscuity, is an important trait underlying terrestrial plant invasions. To test whether host promiscuity may be important in macroalgal invasions, we experimentally simulated an invasion in a common garden setting, using the widespread invasive macroalga Agarophyton vermiculophyllum as a model invasive seaweed holobiont. After disturbing the microbiota of individuals from native and non-native populations with antibiotics, we monitored the microbial succession trajectories in the presence of a new source of microbes. Microbial communities were strongly impacted by the treatment and changed compositionally and in terms of diversity but recovered functionally by the end of the experiment in most respects. Beta-diversity in disturbed holobionts strongly decreased, indicating that different populations configure more similar –or more common– microbial communities when exposed to the same conditions. This decline in beta-diversity occurred not only more rapidly, but was also more pronounced in non-native populations, while individuals from native populations retained communities more similar to those observed in the field. This study demonstrates that microbial communities of non-native A. vermiculophyllum are more flexibly adjusted to the environment and suggests that an intraspecific increase in host promiscuity has promoted the invasion process of A. vermiculophyllum. This phenomenon may be important among invasive macroalgal holobionts in general.
  • Sing-Pei Yu, Masahiro Nakaoka, Benny K.K. Chan
    Environmental Pollution 268 115865 - 115865 2021年01月 [査読有り]
  • Martin Dorber, Francesca Verones, Masahiro Nakaoka, Kenji Sudo
    Remote Sensing Applications: Society and Environment 20 100416 - 100416 2020年11月 [査読有り]
  • Kenji Sudo, Masahiro Nakaoka
    Ecological Research 35 6 994 - 1000 2020年11月 [査読有り]
  • Chihiro Haga, Marimi Maeda, Wataru Hotta, Takahiro Inoue, Takanori Matsui, Takashi Machimura, Masahiro Nakaoka, Junko Morimoto, Hideaki Shibata, Shizuka Hashimoto, Osamu Saito
    Frontiers in Ecology and Evolution 8 2020年05月27日 [査読有り]
     
    The introduction of renewable energy (RE) is essential for building a sustainable society. However, RE can cause conflicts between energy production and biodiversity conservation. This study conducted a scenario analysis to evaluate potential conflicts in the nexuses between energy and biodiversity for the Bekambeushi River watershed located in northeastern Japan. The increasing rate of pastureland abandonment resulting from a declining farmer population is a source of great uncertainty in this area. Two alternative sources of RE were selected to utilize these abandoned pasturelands, each taking a unique approach to meet targets stipulated by regional energy plans, thereby producing different ecological consequences at the landscape scale. Thirty-one RE introduction options were simulated, comprising a range of pastureland abandonment expansion speeds and ratios of solar photovoltaic (PV) plant installation to biomass energy use. These were superimposed using two IPCC representative concentration pathway (RCP) scenarios, 2.6 and 8.5, resulting in 62 scenarios that were summarized as three groups based on the RE supply-demand balance and the ecological impacts. The LANDIS-II model was used to simulate these scenarios from 2016 to 2100. The results indicate that both the rate of pastureland abandonment and the ratio of the two RE sources had a large impact on changes in tree species diversity and the habitat suitability of raptors. Abandoned pastureland converted to tree biomass energy production shifted to pioneer species-dominated forest. The plant species composition of transitional forests varied between the climate scenarios. The higher temperature of the RCP 8.5 scenario toward 2100 prevented the establishment of Betula platyphylla and altered tree species diversity and the habitat suitability of Ketupa blakistoni blakistoni. Biomass energy utilization produced less energy than the demand but increased the three ecological indicators. Solar PV systems provided more energy than the regional demand, but the tree diversity and habitat suitability indices for two raptors declined. However, an appropriate mixture of the two RE sources satisfied the regional energy demand and maintained ecological conditions. Our results suggest that land-energy planning should consider energy-biodiversity nexuses to strike a balance between decarbonization and biodiversity conservation.
  • Bonthond, G., Bayer, T., Krueger-Hadfield, S.A., Barboza, F.R., Nakaoka, M., Valero, M., Wang, G., Künzel, S., Weinberger, F.
    Molecular Ecology 29 11 2020年 [査読有り]
  • Mizuho Namba, Marina Hashimoto, Minako Ito, Kyosuke Momota, Carter Smith, Takefumi Yorisue, Masahiro Nakaoka
    Ecological Research 35 1 61 - 75 2020年01月 [査読有り]
  • Kenji Sudo, Kentaro Watanabe, Norishige Yotsukura, Masahiro Nakaoka
    Ecological Research 35 1 47 - 60 2020年01月 [査読有り]
  • Yutaka Okuzaki, Shoko Nakamura, Masahiro Nakaoka
    Ecological Research 34 5 563 - 574 2019年09月 [査読有り]
     
    The peer-review system ensures the reliability of academic publication. However, authors may be unsatisfied with the duration of peer-review and/or the reviewers' comments, whereas both reviewers and editors have many concerns over peer-reviewing. To provide information to increase the efficiency of the peer-review process for authors, reviewers and editors, we analyzed recent trends in publication and peer-review processes in Ecological Research, and asked Editorial Board members to answer an online questionnaire. The acceptance rate of Original Articles, which accounted for 89.2% of all submissions, was 20.1%, whereas those of Special Features, Data Papers, and Technical Reports were 76.3, 73.7 and 38.3%, respectively. The median number of days to final decision was 168 for accepted manuscripts. The stage when handling editors invited reviewers to review was the longest stage during the peer-review process. This stage was prolonged when potential reviewers declined the invitations to review. The results of the questionnaire revealed that both editors and reviewers felt burdened by the load of peer-reviewing. Most editors encountered declining of peer-review invitations. As the period of assigning reviewers is the most important step in determining the number of days to the final decision, the editorial office should support handling editors to locate reviewers. Motivating reviewers to review manuscripts is another way to speed up the process. Since many respondents indicated that improvements in the logical structure and English standard of manuscripts would facilitate review, authors could improve the process by carefully preparing their manuscripts with consideration to readers, including voluntary reviewers and editors.
  • José H. Muelbert, Nicholas J. Nidzieko, Alicia T. R. Acosta, Stace E. Beaulieu, Angelo F. Bernardino, Elmira Boikova, Thomas G. Bornman, Bruno Cataletto, Klaas Deneudt, Erika Eliason, Alexandra Kraberg, Masahiro Nakaoka, Alessandra Pugnetti, Olivier Ragueneau, Mirco Scharfe, Thomas Soltwedel, Heidi M. Sosik, Angela Stanisci, Kremena Stefanova, Pierre Stéphan, Adrian Stier, Johan Wikner, Adriana Zingone
    Frontiers in Marine Science 6 2019年08月28日 [査読有り]
  • Takehisa Yamakita, Fumiaki Sodeyama, Napakhwan Whanpetch, Kentaro Watanabe, Masahiro Nakaoka
    Botanica Marina 62 4 291 - 307 2019年08月27日 [査読有り]
     
    Abstract Few studies have investigated the long-term temporal dynamics of seagrass beds, especially in Southeast Asia. Remote sensing is one of the best methods for observing these dynamic patterns, and the advent of deep learning technology has led to recent advances in this method. This study examined the feasibility of applying image classification methods to supervised classification and deep learning methods for monitoring seagrass beds. The study site was a relatively natural seagrass bed in Hat Chao Mai National Park, Trang Province, Thailand, for which aerial photographs from the 1970s were available. Although we achieved low accuracy in differentiating among various densities of vegetation coverage, classification related to the presence of seagrass was possible with an accuracy of 80% or more using both classification methods. Automatic classification of benthic cover using deep learning provided similar or better accuracy than that of the other methods even when grayscale images were used. The results also demonstrate that it is possible to monitor the temporal dynamics of an entire seagrass area, as well as variations within sub-regions, located in close proximity to a river mouth.
  • J. Emmett Duffy, Lisandro Benedetti-Cecchi, Joaquin Trinanes, Frank E. Muller-Karger, Rohani Ambo-Rappe, Christoffer Boström, Alejandro H. Buschmann, Jarrett Byrnes, Robert G. Coles, Joel Creed, Leanne C. Cullen-Unsworth, Guillermo Diaz-Pulido, Carlos M. Duarte, Graham J. Edgar, Miguel Fortes, Gustavo Goni, Chuanmin Hu, Xiaoping Huang, Catriona L. Hurd, Craig Johnson, Brenda Konar, Dorte Krause-Jensen, Kira Krumhansl, Peter Macreadie, Helene Marsh, Len J. McKenzie, Nova Mieszkowska, Patricia Miloslavich, Enrique Montes, Masahiro Nakaoka, Kjell Magnus Norderhaug, Lina M. Norlund, Robert J. Orth, Anchana Prathep, Nathan F. Putman, Jimena Samper-Villarreal, Ester A. Serrao, Frederick Short, Isabel Sousa Pinto, Peter Steinberg, Rick Stuart-Smith, Richard K. F. Unsworth, Mike van Keulen, Brigitta I. van Tussenbroek, Mengqiu Wang, Michelle Waycott, Lauren V. Weatherdon, Thomas Wernberg, Siti Maryam Yaakub
    Frontiers in Marine Science 6 2019年07月04日 [査読有り]
  • Heather Glon, Yamaguchi Haruka, Marymegan Daly, Masahiro Nakaoka
    Hydrobiologia 830 1 303 - 315 2019年03月 [査読有り]
  • Maria Emilia Röhr, Marianne Holmer, Julia K. Baum, Mats Björk, Katharyn Boyer, Diana Chin, Lia Chalifour, Stephanie Cimon, Mathieu Cusson, Martin Dahl, Diana Deyanova, J. Emmet Duffy, Johan S. Eklöf, Julie K. Geyer, John N. Griffin, Martin Gullström, Clara M. Hereu, Masakazu Hori, Kevin A. Hovel, A. Randall Hughes, Pablo Jorgensen, Stephanie Kiriakopolos, Per-Olav Moksnes, Masahiro Nakaoka, Mary I. O'Connor, Bradley Peterson, Katrin Reiss, Pamela L. Reynolds, Francesca Rossi, Jennifer Ruesink, Rui Santos, John J. Stachowicz, Fiona Tomas, Kun-Seop Lee, Richard K. F. Unsworth, Christoffer Boström
    Global Biogeochemical Cycles 32 10 1457 - 1475 2018年10月 [査読有り]
  • Lina Mtwana Nordlund, Emma L. Jackson, Masahiro Nakaoka, Jimena Samper-Villarreal, Pedro Beca-Carretero, Joel C. Creed
    Marine Pollution Bulletin 134 145 - 151 2018年09月 [査読有り]
  • Mizuho Namba, Masahiro Nakaoka
    PLOS ONE 13 8 e0201791 - e0201791 2018年08月07日 [査読有り]
  • Erik E. Sotka, Aaron W. Baumgardner, Paige M. Bippus, Christophe Destombe, Elizabeth A. Duermit, Hikaru Endo, Ben A. Flanagan, Mits Kamiya, Lauren E. Lees, Courtney J. Murren, Masahiro Nakaoka, Sarah J. Shainker, Allan E. Strand, Ryuta Terada, Myriam Valero, Florian Weinberger, Stacy A. Krueger‐Hadfield
    Evolutionary Applications 11 5 781 - 793 2018年06月 [査読有り]
  • Carter S. Smith, Minako Ito, Mizuho Namba, Masahiro Nakaoka
    PLOS ONE 13 5 e0197753 - e0197753 2018年05月24日 [査読有り]
  • Jennifer L. Ruesink, John J. Stachowicz, Pamela L. Reynolds, Christoffer Boström, Mathieu Cusson, James Douglass, Johan Eklöf, Aschwin H. Engelen, Masakazu Hori, Kevin Hovel, Katrin Iken, Per-Olav Moksnes, Masahiro Nakaoka, Mary I. O'Connor, Jeanine L. Olsen, Erik E. Sotka, Matthew A. Whalen, J. Emmett Duffy
    Oikos 127 3 364 - 374 2018年03月 [査読有り]
  • Venus Leopardas, Masakazu Hori, Hiroshi Mukai, Yoshiyuki Tanaka, Ken-ichi Yokoi, Misuzu Aoki, Naoto Sato, Napakhwan Whanpetch, Masahiro Nakaoka
    Ecological Research 33 1 105 - 117 2018年01月 [査読有り]
     
    © 2017, The Ecological Society of Japan. Broad scale studies in seagrass benthic macrofauna are important for future regional marine conservation. We examined spatial variation in the community structure of seagrass-associated benthic macroinvertebrates collected by sediment coring in 2010 at six seagrass sites of Japan covering the latitudinal range of 24°–43°N. Total species richness and ES(50) at site level did not show clear site variations and relationship with latitude. At core level, site variations of mean species richness, ES(50), Simpson diversity and abundance showed inconsistent pattern, but with more cases of statistically significant association with latitude. Variations were generally influenced by the seagrass species, often among subtropical species, among temperate Zostera species, and between Zostera and subtropical species. Finally, the community composition differed significantly across all sites and community similarity decreased rapidly with geographic distance, with only 5% similarity retained at the distance of 400 km. The dissimilarity among sites was higher with the similar distance compared to other types of coastal communities such as rocky intertidal assemblages, which is associated with minor occurrence of species with broad distributional range.
  • Masahiro Nakaoka, Kenji Sudo, Mizuho Namba, Hideaki Shibata, Futoshi Nakamura, Satoshi Ishikawa, Mitsutaku Makino, Hiroya Yamano, Shin-ichiro S. Matsuzaki, Takehisa Yamakita, Xiubo Yu, Xiyong Hou, Xiaowei Li, Jon Brodie, Keiichiro Kanemoto, Dan Moran, Francesca Verones
    Ecological Research 33 1 35 - 49 2018年01月 [査読有り]
     
    The expanding economical activities have accelerated losses of biodiversity and ecosystem services, which are especially pronounced in Asia. To find solutions to stop these losses, a group of scientists studying both ecological and social sciences has launched an interdisciplinary research network, entitled TSUNAGARI (Trans-System, UNified Approach for Global and Regional Integration of social-ecological study toward sustainable use of biodiversity and ecosystem services). The project is based on two main perspectives: (1) integrating different disciplines of environmental research across multiple spatial scales, and (2) evaluating the importance of ecosystem connectivity between land and ocean for biodiversity and ecosystem services. The integrative studies have been started as follows: (1) integrating global-scale analyses of biodiversity and economy by developing GIS-based footprint analysis, (2) establishing the link between the studies of local good practices of ecosystem management and life cycle assessment on ecosystem good and services, (3) linking local-scale ecosystem studies to decision making processes for sustainable society by multiple stakeholders, and (4) upscaling local analyses of ecosystem processes to broad-scale analyses of ecosystem patterns. The proposed approaches are considered effective to solve problems that impede conservation of biodiversity and sustainable use of multiple ecosystem services in various situations although we also find some gaps such as regional biases in biodiversity data and involvement of different types of stakeholders. By overcoming the major bottlenecks, we believe the new integrated approaches will promote conservation and sustainable management of biodiversity and ecosystem services research, and contribute to advance decision-making processes from local communities to international levels.
  • Pamela L. Reynolds, John J. Stachowicz, Kevin Hovel, Christoffer Boström, Katharyn Boyer, Mathieu Cusson, Johan S. Eklöf, Friederike G. Engel, Aschwin H. Engelen, Britas Klemens Eriksson, F. Joel Fodrie, John N. Griffin, Clara M. Hereu, Masakazu Hori, Torrance C. Hanley, Mikhail Ivanov, Pablo Jorgensen, Claudia Kruschel, Kun‐Seop Lee, Karen McGlathery, Per‐Olav Moksnes, Masahiro Nakaoka, Mary I. O'Connor, Nessa E. O'Connor, Robert J. Orth, Francesca Rossi, Jennifer Ruesink, Erik E. Sotka, Jonas Thormar, Fiona Tomas, Richard K. F. Unsworth, Matthew A. Whalen, J. Emmett Duffy
    Ecology 99 1 29 - 35 2018年01月 [査読有り]
  • Xiaodong Fang, Xiyong Hou, Xiaowei Li, Wan Hou, Masahiro Nakaoka, Xiubo Yu
    Ecological Research 33 1 51 - 61 2018年01月
  • Sahadev Sharma, Kazuo Nadaoka, Masahiro Nakaoka, Wilfredo H. Uy, Richard A. MacKenzie, Daniel A. Friess, Miguel D. Fortes
    HYDROBIOLOGIA 803 1 359 - 371 2017年11月 [査読有り][通常論文]
     
    The Philippines has lost nearly 70% of its natural mangrove cover since the early 1900s. As a result, large investments have been made to restore mangrove forests and the many ecosystem services that they provide. Most of these restoration efforts have been through outplanting of Rhizophora sp. seedlings, many of which have failed because the proper hydrological and ecological conditions were not properly assessed. Other afforestation projects involved planting seedlings in inappropriate places (e.g., seagrass beds, mudflats) that resulted in replacing one valuable ecosystem with another. The aim of this research was to investigate the growth of 3-, 9-, and 21-year-old afforested stands of Rhizophora spp. mangrove forest. We also investigated the impact of these plantations on local seagrass beds. The total aboveground biomass was 42.6, 74.4, and 111.7 Mg ha(-1) for the 3-, 9-, and 21-year-old mangrove stands, respectively. Seagrass bed cover decreased under the closed canopy of the mangrove due to reduced photosynthetically active radiation and competition for growing space. This study shows that mangroves can grow to some extent on seagrass beds, though mangrove planting in these areas could eventually lead to seagrass loss. Thus, mangroves should not be planted in areas that are naturally occupied by other ecologically important ecosystems. The purpose of mangrove restoration should be clear and efforts should be focused on formerly deforested or degraded areas. Additional studies are needed from different locations to understand how mangrove planting in seagrass beds impacts growth performance and ecological functions of the latter ecosystem.
  • Masaaki Sato, Kentaro Honda, Wilfredo H. Uy, Darwin I. Baslot, Tom G. Genovia, Yohei Nakamura, Lawrence Patrick C. Bernardo, Hiroyuki Kurokochi, Allyn Duvin S. Pantallano, Chunlan Lian, Kazuo Nadaoka, Masahiro Nakaoka
    ECOLOGY AND EVOLUTION 7 19 7859 - 7871 2017年10月 [査読有り][通常論文]
     
    The establishment of marine protected areas (MPAs) can often lead to environmental differences between MPAs and fishing zones. To determine the effects on marine dispersal of environmental dissimilarity between an MPA and fishing zone, we examined the abundance and recruitment patterns of two anemonefishes (Amphiprion frenatus and A.perideraion) that inhabit sea anemones in different management zones (i.e., an MPA and two fishing zones) by performing a field survey and a genetic parentage analysis. We found lower levels of abundance per anemone in the MPA compared to the fishing zones for both species (n=1,525 anemones, p=.032). The parentage analysis also showed that lower numbers of fishes were recruited from the fishing zones and outside of the study area into each anemone in the MPA than into each anemone in the fishing zones (n=1,525 anemones, p<.017). However, the number of self-recruit production per female did not differ between the MPA and fishing zones (n=384 females, p=.516). Because the ocean currents around the study site were unlikely to cause a lower settlement intensity of larvae in the MPA, the ocean circulation was not considered crucial to the observed abundance and recruitment patterns. Instead, stronger top-down control and/or a lower density of host anemones in the MPA were potential factors for such patterns. Our results highlight the importance of dissimilarity in a marine environment as a factor that affects connectivity.
  • Shasha Wang, Florian Weinberger, Luyang Xiao, Masahiro Nakaoka, Gaoge Wang, Stacy A. Krueger-Hadfield, Erik E. Sotka, Dapeng Bian, Mark Lenz
    MARINE BIOLOGY 164 10 2017年10月 [査読有り][通常論文]
     
    The susceptibility of native and non-native populations of the red alga Gracilaria vermiculophylla to fouling was compared in common garden experiments. Native and non-native algae were enclosed into dialysis membrane tubes, and the tubes were exposed to natural fouling. Fouling on the outside of the tubes was mediated by chemical compounds excreted by G. vermiculophylla that diffused through the membranes. Fouling pressure was significantly higher in the Kiel Fjord (non-native range) than in Akkeshi Bay (native range), but, at both sites, tubes containing non-native G. vermiculophylla were less fouled than those with native conspecifics. This is the first in situ evidence that susceptibility to fouling differs between native and non-native populations of an aquatic organism. The technique of enclosing organisms into dialysis tubes represents a simple, efficient and accurate way to test chemical antifouling defenses and could possibly be applied to other organisms.
  • Kentaro Honda, Wilfredo H. Uy, Darwin I. Baslot, Allyn Duvin S. Pantallano, Masaaki Sato, Yohei Nakamura, Masahiro Nakaoka
    FISHERIES SCIENCE 83 4 523 - 535 2017年07月 [査読有り][通常論文]
     
    A passive acoustic telemetry survey was conducted to determine occurrence patterns of commercially important fishes on a steep reef slope along a marine protected area (MPA) in the southern Philippines, where the outer reef edge is often set as an offshore MPA boundary. Based on 4-61 days of tracking data from 21 detected individuals of five species (Lutjanus argentimaculatus, Lutjanus monostigma, Lethrinus atkinsoni, Lethrinus obsoletus, and Siganus guttatus; 20.7-69.2 cm fork length) caught near the reef slope of the MPA, S. guttatus occurred most frequently on the reef flat of the MPA, whereas all individuals of the four lutjanid and lethrinid species were primarily (99.4-100%) detected near the reef slope, and nine individuals (56.3% of these four species) of three of these species (not L. obsoletus) most likely used the shallow (ae<currency>10 m) and deep (ae<yen>20 m) layers, and thus, middle layers of the slope. These findings indicate that commercially important lutjanid and lethrinid species predominantly and vertically used the areas near the reef slope, suggesting the importance of fully including reef slopes in MPAs to enhance their effectiveness for the conservation of such fishes.
  • Keiichi Fukaya, J. Andrew Royle, Takehiro Okuda, Masahiro Nakaoka, Takashi Noda
    METHODS IN ECOLOGY AND EVOLUTION 8 6 757 - 767 2017年06月 [査読有り][通常論文]
     
    1. Estimation of transition probabilities of sessile communities seems easy in principle but may still be difficult in practice because resampling error (i.e. a failure to resample exactly the same location at fixed points) may cause significant estimation bias. Previous studies have developed novel analytical methods to correct for this estimation bias. However, they did not consider the local structure of community composition induced by the aggregated distribution of organisms that is typically observed in sessile assemblages and is very likely to affect observations. 2. We developed a multistate dynamic site occupancy model to estimate transition probabilities that accounts for resampling errors associated with local community structure. The model applies a nonparametric multivariate kernel smoothing methodology to the latent occupancy component to estimate the local state composition near each observation point, which is assumed to determine the probability distribution of data conditional on the occurrence of resampling error. 3. By using computer simulations, we confirmed that an observation process that depends on local community structure may bias inferences about transition probabilities. By applying the proposed model to a real data set of intertidal sessile communities, we also showed that estimates of transition probabilities and of the properties of community dynamics may differ considerably when spatial dependence is taken into account. 4. Results suggest the importance of accounting for resampling error and local community structure for developing management plans that are based on Markovian models. Our approach provides a solution to this problem that is applicable to broad sessile communities. It can even accommodate an anisotropic spatial correlation of species composition, and may also serve as a basis for inferring complex nonlinear ecological dynamics.
  • Huamei Shao, Kenji Minami, Hokuto Shirakawa, Takashi Maeda, Toshiaki Ohmura, Yoshikazu Fujikawa, Norishige Yotsukura, Masahiro Nakaoka, Kazushi Miyashita
    JOURNAL OF MARINE SCIENCE AND TECHNOLOGY-TAIWAN 25 3 343 - 351 2017年06月 [査読有り][通常論文]
     
    Acoustic methods can be used to assess seaweed meadows. The accuracy of the methods is a key factor in the estimation of seaweed distribution and conditions. We obtained and verified thickness and spatial distribution values measured using an echo sounder. We determined the thickness of seaweed growing in the coastal waters off Higashidoori-mura, Aomori, Japan on June 5-6, 2013. Acoustic data were collected using an on-board quantitative echosounder at 120 kHz. The thickness was also directly measured at 14 points. The root mean square error (RMSE) of the thickness determined by the acoustic and direct methods was calculated. A survey to determine the spatial distribution was performed in Miyako-shi, Iwate on July 18, 2014. The estimated spatial distribution was determined from the thickness data collected by the acoustic method of varied transect lines by changing transect orientation and intervals. The kelp forest distribution was also observed directly at 106 points. Then, the concordance rates of the visual observations and estimated spatial distribution were obtained. The RMSE of the acoustic and directly measured thickness of the kelp forests (Saccharina japonica), was 0.06 m, similar to the vertical resolution of the echosounder. The concordance rate between the acoustic and directly measured values was 92% when the maximum transect interval was 21 m. Smaller transect intervals yielded higher accuracy. High accuracy for the thickness and acoustically derived spatial distribution were obtained by the acoustic method when suitable thresholds were used, which has important applications for the evaluation of seaweed stands.
  • Shasha Wang, Gaoge Wang, Florian Weinberger, Dapeng Bian, Masahiro Nakaoka, Mark Lenz
    JOURNAL OF ECOLOGY 105 2 445 - 457 2017年03月 [査読有り][通常論文]
     
    Epibiosis in the marine environment is a stressor that may determine invasion success in introduced species. Previous comparisons showed resistance to epibionts can be higher in non-native than in resident seaweed species, but we do not know whether it is an intrinsic trait of the non-natives or it has been acquired during the invasion process. To elucidate this question, a comparison between native and non-native populations of the same species is needed. Resistance against two groups of epiphytes was assessed in living thalli and in artificial substrata coated with surface extracts, both gained from four Asian (native) and four European (non-native) populations of the red alga Gracilaria vermiculophylla. Two diatom species and two filamentous macroalgae were used as micro-and macro-epiphytes, and one of each type was collected in Asia, while the other came from Europe. Laboratory assays were done in both distributional ranges of G. vermiculophylla and in different seasons. We used G. vermiculophylla from four populations in each range and used a fully crossed design with the factors (i) `Origin of Gracilaria', (ii) `Origin of epiphytes', (iii) `Season' and (iv) `Solvent used for extraction'. Both groups of epiphytes, regardless of their origin, attached less to living thalli and to surface extracts from non-native G. vermiculophylla. Fewer diatoms attached to hexane-based extracts, while fewer Ceramium filaments settled on extracts gained with dichloromethane. Synthesis. Our results show for the first time that non-native individuals of a marine organism are better defended against epiphytes than native conspecifics. Furthermore, we found evidence that at least a part of the defence is based on extractable secondary metabolites. We discuss several mechanisms that could explain the increased resistance to epiphytes in non-native individuals, including the release from enemies in the non-native range, which could lead to an increase in algal performance during the invasion process. We suggest that an enhanced defence against epiphytes after introduction is one reason for G. vermiculophylla's invasion success. Our observation may also apply to other basibiont-epibiont and host-enemy systems, including plant-plant, plant-animal and animal-animal interactions, in aquatic environments and could be a key (f)eature of bioinvasions.
  • Atsushi Fukuta, Yasuhiro Kamimura, Masakazu Hori, Masahiro Nakaoka, Tsutomu Noda, Yoh Yamashita, Tsuguo Otake, Jun Shoji
    FISHERIES OCEANOGRAPHY 26 1 65 - 68 2017年01月 [査読有り][通常論文]
     
    Oceanographic conditions can affect spatial variability in fish community structures by influencing the temperature-dependent latitudinal distribution of adult fishes and transport during their young stages. In order to examine latitudinal variability in the fish community structure within a single coastal ecosystem, quantitative sampling was conducted in the subtidal zone of seagrass Zostera marina beds over a broad latitudinal scale (31.31-43.0 degrees N: from subtropical to sub-boreal zones, covering 80% of the latitudinal range of seagrass distribution in Japan) in the western North Pacific based on a uniform methodology. Cluster analysis with the similarity of fish communities showed that 13 sampling sites were divided into two clusters. The border between the two clusters corresponded with the area of mixing of two dominant currents, Oyashio and Kuroshio, which form a border between the warm temperate zone and the cool temperate zone off the Pacific coast of Japan. Oceanographic properties, such as major currents off the coast, are suggested to affect the latitudinal variability in the fish communities in the coastal ecosystem in the western North Pacific.
  • Kyosuke Momota, Masahiro Nakaoka
    PEERJ 5 1 e2952  2017年01月 [査読有り][通常論文]
     
    Eelgrass (Zostera marina) beds are known to have high ecological and economical values within coastal ecosystems of the temperate northern hemisphere although their biodiversity and functions varied greatly from sites to sites. The variation in the biomass, abundance and diversity of mobile invertebrates in eelgrass beds has been examined in relation to various abiotic and biotic factors, such as water temperature, salinity, eelgrass biomass and epiphytic microalgae presence. However, the importance of sessil e epibionts, such as macroalgae and calcific spirorbid polychaetes attached to eelgrass blades, has not been the focus of Previous studies. In the Present study, we examined the effects of three different sessile epibionts, namely, branched red algae, filamentous green algae, and calcific spirorbid polychaetes, on the biomass and diversity of mobile invertebrates in the eelgrass beds of Akkeshi in northeastern Japan. The relationships between seven abiotic and biotic variables including three types of epibionts, and biomass of 11 dominant mobile invertebrate species as well as three community-level variables (the total biomass of mobile invertebrates, species richness and the Shannon Wiener species diversity index) were analyzed using a linear.mixed model. Our results show that branched red algae are correlated with Pontogenea rostrata, Lacuna spp., N ereis sp., Syllis sp. and the total biomass of mobile invertebrates, filamentous green algae with P. rostrata, Ansola angustata and the, species' diversity of mobile invertebrates, and spirorbid polychaetes with A. angustata, Lacuna spp., Siphonacmea oblongata, Syllis sp., the species richness and diversity of mobile invertebrates. The effect size of the epibionts was similar or even higher than that of abiotic and eelgrass factors on the total biomass of mobile invertebrates, species richness, species diversity and most of dominant invertebrate populations across the taxonomic groups. Consequently, epibiotic macroalgae and spirorbid polychaetes can be good predictors of the variation in the total biomass, species richness and species diversity of mobile invertebrates and the biomass of major dominant species, especially for species that have a relatively high dependency on eelgrass blades. These results suggest that the different functional groups of sessile epibionts have significant roles in determining the biomass and diversity of mobile invertebrates in eelgrass beds.
  • Norishige Yotsukura, Takashi Maeda, Tsuyoshi Abe, Masahiro Nakaoka, Tadashi Kawai
    JOURNAL OF APPLIED PHYCOLOGY 28 5 3043 - 3055 2016年10月 [査読有り][通常論文]
     
    The genetic diversity of Saccharina japonica inhabiting the Hokkaido coastline and the surrounding area was investigated by AFLP and SSR analyses. A STRUCTURE analysis based on the AFLP data identified two clusters in the species, although a few local populations with genetic structures different from that of the neighboring populations were detected. The two clusters could be identified even within each current variety. In the SSR analysis, genetic variation in nucleotide sequences in all samples was located in four DNA regions (MS10, MS11, MS16, and MS29), and it is thought that these regions can be used as markers to detect individual-level variation in S. japonica. The STRUCTURE analysis of the SSR data identified four clusters in the species. Since the geographical distribution of these four different clusters does not correspond exactly to the currently recognized varieties in this species, it will be necessary to re-evaluate the distribution of the varieties of S. japonica.
  • Ryosuke Sahara, Keiichi Fukaya, Takehiro Okuda, Masakazu Hori, Tomoko Yamamoto, Masahiro Nakaoka, Takashi Noda
    ECOGRAPHY 39 5 487 - 495 2016年05月 [査読有り][通常論文]
     
    Many marine benthic invertebrates pass through a planktonic larval stage whereas others spend their entire lifetimes in benthic habitats. Recent studies indicate that non-planktonic species show relatively greater fine-scale patchiness than do planktonic species, but the underlying mechanisms remain unknown. One hypothesis for such a difference is that larval dispersal enhances the connectivity of populations and buffers population fluctuations and reduces local extinction risk, consequently increasing patch occupancy rate and decreasing spatial patchiness. If this mechanism does indeed play a significant role, then the distribution of non-planktonic species should be more aggregated - both temporally and spatially - than the distribution of species with a planktonic larval stage. To test this prediction, we compared 1) both the spatial and the temporal abundance-occupancy relationships and 2) both the spatial and the temporal mean-variance relationships of population size across species of rocky intertidal gastropods with differing dispersive traits from the Pacific coast of Japan. We found that, compared to planktonic species, non-planktonic species exhibited 1) a smaller occupancy rate for any given level of mean population size and 2) greater variations in population size, both spatially and temporally. This suggests that the macroecological patterns observed in this study (i.e. the abundance-occupancy relationships and mean-variance relationships of population size across species) were shaped by the effect of larval dispersal dampening population fluctuation, which works over both space and time. While it has been widely assumed that larval dispersal enhances population fluctuations, larval dispersal may in fact enhance the connectively of populations and buffer population fluctuations and reduce local extinction risks.
  • Venus Leopardas, Kentaro Honda, Gay Amabelle Go, Klenthon Bolisay, Allyn Duvin Pantallano, Wilfredo Uy, Miguel Fortes, Masahiro Nakaoka
    MARINE POLLUTION BULLETIN 105 1 310 - 318 2016年04月 [査読有り][通常論文]
     
    This study examined the variation of macrofaunal communities in sea grass beds along a pollution gradient in Bolinao, northwestern Philippines. We established four stations and compared the diversity and abundance of macrofauna between them. The Shannon diversity index in the least polluted station was more than twice higher than that in the most polluted one. Abundance was more than thrice higher in the most polluted station. The species composition generally varied, with community difference explained largely by the predominance of the filter-feeding bivalve Gafrarium pectinatum and polychaete Capitella capitata. Species heterogeneity was reduced along the pollution gradient by approximately 19% from the least polluted to the most polluted station. This reduction indicates biodiversity alteration, which has a significant impact on ecosystem functioning. Aspects of species heterogeneity should be considered in environmental impact assessments and the management of coastal areas encountered with anthropogenic disturbances. (C) 2016 Elsevier Ltd. All rights reserved.
  • Marieke M. van Katwijk, Anitra Thorhaug, Nuria Marba, Robert J. Orth, Carlos M. Duarte, Gary A. Kendrick, Inge H. J. Althuizen, Elena Balestri, Guillaume Bernard, Marion L. Cambridge, Alexandra Cunha, Cynthia Durance, Wim Giesen, Qiuying Han, Shinya Hosokawa, Wawan Kiswara, Teruhisa Komatsu, Claudio Lardicci, Kun-Seop Lee, Alexandre Meinesz, Masahiro Nakaoka, Katherine R. O'Brien, Erik I. Paling, Chris Pickerell, Aryan M. A. Ransijn, Jennifer J. Verduin
    JOURNAL OF APPLIED ECOLOGY 53 2 567 - 578 2016年04月 [査読有り][通常論文]
     
    In coastal and estuarine systems, foundation species like seagrasses, mangroves, saltmarshes or corals provide important ecosystem services. Seagrasses are globally declining and their reintroduction has been shown to restore ecosystem functions. However, seagrass restoration is often challenging, given the dynamic and stressful environment that seagrasses often grow in. From our world-wide meta-analysis of seagrass restoration trials (1786 trials), we describe general features and best practice for seagrass restoration. We confirm that removal of threats is important prior to replanting. Reduced water quality (mainly eutrophication), and construction activities led to poorer restoration success than, for instance, dredging, local direct impact and natural causes. Proximity to and recovery of donor beds were positively correlated with trial performance. Planting techniques can influence restoration success. The meta-analysis shows that both trial survival and seagrass population growth rate in trials that survived are positively affected by the number of plants or seeds initially transplanted. This relationship between restoration scale and restoration success was not related to trial characteristics of the initial restoration. The majority of the seagrass restoration trials have been very small, which may explain the low overall trial survival rate (i.e. estimated 37%). Successful regrowth of the foundation seagrass species appears to require crossing a minimum threshold of reintroduced individuals. Our study provides the first global field evidence for the requirement of a critical mass for recovery, which may also hold for other foundation species showing strong positive feedback to a dynamic environment.Synthesis and applications. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration.
  • Manuel Maass, Patricia Balvanera, Patrick Bourgeron, Miguel Equihua, Jacques Baudry, Jan Dick, Martin Forsius, Lubos Halada, Kinga Krauze, Masahiro Nakaoka, Daniel E. Orenstein, Terry W. Parr, Charles L. Redman, Ricardo Rozzi, Margarida Santos-Reis, Anthony M. Swemmer, Angheluta Vadineanu
    ECOLOGY AND SOCIETY 21 3 2016年 [査読有り][通常論文]
     
    The International Long-Term Ecological Research (ILTER) network comprises > 600 scientific groups conducting site-based research within 40 countries. Its mission includes improving the understanding of global ecosystems and informs solutions to current and future environmental problems at the global scales. The ILTER network covers a wide range of social-ecological conditions and is aligned with the Programme on Ecosystem Change and Society (PECS) goals and approach. Our aim is to examine and develop the conceptual basis for proposed collaboration between ILTER and PECS. We describe how a coordinated effort of several contrasting LTER site-based research groups contributes to the understanding of how policies and technologies drive either toward or away from the sustainable delivery of ecosystem services. This effort is based on three tenets: transdisciplinary research; cross-scale interactions and subsequent dynamics; and an ecological stewardship orientation. The overarching goal is to design management practices taking into account trade-offs between using and conserving ecosystems toward more sustainable solutions. To that end, we propose a conceptual approach linking ecosystem integrity, ecosystem services, and stakeholder well-being, and as a way to analyze trade-offs among ecosystem services inherent in diverse management options. We also outline our methodological approach that includes: (i) monitoring and synthesis activities following spatial and temporal trends and changes on each site and by documenting cross-scale interactions; (ii) developing analytical tools for integration; (iii) promoting trans-site comparison; and (iv) developing conceptual tools to design adequate policies and management interventions to deal with trade-offs. Finally, we highlight the heterogeneity in the social-ecological setting encountered in a subset of 15 ILTER sites. These study cases are diverse enough to provide a broad cross-section of contrasting ecosystems with different policy and management drivers of ecosystem conversion; distinct trends of biodiversity change; different stakeholders' preferences for ecosystem services; and diverse components of well-being issues.
  • J. Emmett Duffy, Pamela L. Reynolds, Christoffer Bostroem, James A. Coyer, Mathieu Cusson, Serena Donadi, James G. Douglass, Johan S. Ekloef, Aschwin H. Engelen, Britas Klemens Eriksson, Stein Fredriksen, Lars Gamfeldt, Camilla Gustafsson, Galice Hoarau, Masakazu Hori, Kevin Hovel, Katrin Iken, Jonathan S. Lefcheck, Per-Olav Moksnes, Masahiro Nakaoka, Mary I. O'Connor, Jeanine L. Olsen, J. Paul Richardson, Jennifer L. Ruesink, Erik E. Sotka, Jonas Thormar, Matthew A. Whalen, John J. Stachowicz
    ECOLOGY LETTERS 18 7 696 - 705 2015年07月 [査読有り][通常論文]
     
    Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.
  • Toshihiro Miyajima, Masakazu Hori, Masami Hamaguchi, Hiromori Shimabukuro, Hiroshi Adachi, Hiroya Yamano, Masahiro Nakaoka
    GLOBAL BIOGEOCHEMICAL CYCLES 29 4 397 - 415 2015年04月 [査読有り][通常論文]
     
    Organic carbon (OC) stored in the sediments of seagrass meadows has been considered a globally significant OC reservoir. However, the sparsity and regional bias of studies on long-term OC accumulation in coastal sediments have limited reliable estimation of the capacity of seagrass meadows as a global OC sink. We evaluated the amount and accumulation rate of OC in sediment of seagrass meadows and adjacent areas in East and Southeast Asia. In temperate sites, the average OC concentration in the top 30 cm of sediment was higher in seagrass meadows (780-1080 mmol g(-1)) than in sediments without seagrass cover (52-430 mmol g(-1)). The average OC in the top 30 cm of subtropical and tropical seagrass meadow sediments ranged from 140 to 440 mmol g(-1). Carbon isotope mass balancing suggested that the contribution of seagrass-derived carbon to OC stored in sediments was often relatively minor (temperate: 10-40%; subtropical: 35-82%; tropical: 4-34%) and correlated to the habitat type, being particularly low in estuarine habitats. Stock of OC in the top meter of sediment of all the studied meadows ranged from 38 to 120 Mg ha(-1). The sediment accumulation rates were estimated by radiocarbon dating of six selected cores (0.32-1.34 mm yr(-1)). The long-term OC accumulation rates calculated from the sediment accumulation rate and the top 30 cm average OC concentration for the seagrass meadows (24-101 kg ha(-1) yr(-1)) were considerably lower than the OC accumulation rates previously reported for Mediterranean Posidonia oceanica meadows (580 kg ha(-1) yr(-1) on average). Current estimates for the global carbon sink capacity of seagrass meadows, which rely largely on Mediterranean studies, may be considerable overestimations.
  • Shinya Hosokawa, Masahiro Nakaoka, Eiichi Miyoshi, Tomohiro Kuwae
    MARINE ECOLOGY PROGRESS SERIES 523 41 - 56 2015年03月 [査読有り][通常論文]
     
    Seed production and dispersal are key processes in plant population dynamics and gene flow. However, few quantitative studies have followed these processes in aquatic plants. We investigated the abundance of seeds produced and dispersed by the seagrass Zostera marina L. at a protected site within an enclosed bay. We also examined the buoyancy potential of seed dispersal units (diaspores) in the laboratory. Field observations showed that 31% of the total potentially produced seeds were dispersed as decayed reproductive shoots on the sea bottom of the parent bed, whereas 14% were dispersed in spathes (a component of reproductive shoots; seeds are contained inside) detached from live reproductive shoots. However, more than half of the dispersed spathes were negatively buoyant because of the weight of the ripe seeds they contained. Thus, <6% of potentially produced seeds were dispersed by rafting away from the parent bed. The abundance of ripe seeds dispersed was comparable to that of seeds in the parent bed sediment. The fate of the remaining 54% of total potentially produced seeds was not detected, and they were assumed to be immature or to have been consumed by herbivores. Fewer than 5% of the dispersed seeds had germinated. Our results show that most seeds were dispersed within the parent bed, supporting one of the fitness-related seed-dispersal hypotheses, namely that dispersal mechanisms play a role in bed maintenance and increased genetic diversity.
  • Mikio Watai, Yohei Nakamura, Kentaro Honda, Klenthon O. Bolisay, Toshihiro Miyajima, Masahiro Nakaoka, Miguel D. Fortes
    FISHERIES SCIENCE 81 1 43 - 51 2015年01月 [査読有り][通常論文]
     
    The present study clarified the impacts of aquaculture pollution on the surrounding seagrass bed fishes by comparing the diet, growth, and abundance of Parupeneus barberinus and Acreichthys tomentosus along a pollution gradient caused by intensive milkfish Chanos chanos farming in Bolinao, northwestern Philippines. The two fish species and potential food items exhibited increasingly enriched delta C-13 values with greater distance from the milkfish farming area, thereby indicating that stable carbon isotopes facilitated good discrimination between fishes from polluted and unpolluted areas. P. barberinus fed on epi-/benthic crustaceans, whereas A. tomentosus consumed a wide range of food, including invertebrates and plant materials in the unpolluted areas, but zooplankton were the most commonly predated food items in the polluted areas for both species. The growth rate of P. barberinus was marginally lower in the polluted area than in the unpolluted area, whereas that of A. tomentosus did not differ between the two areas. The abundance of both species did not differ significantly between the polluted and unpolluted areas, but the growth patterns of the two species suggest that A. tomentosus has greater physiological tolerance of the polluted environment than P. barberinus.
  • Takehisa Yamakita, Hiroyuki Yamamoto, Masahiro Nakaoka, Hiroya Yamano, Katsunori Fujikura, Kiyotaka Hidaka, Yuichi Hirota, Tadafumi Ichikawa, Shigeho Kakehi, Takahiko Kameda, Satoshi Kitajimal, Kazuhiro Kogure, Teruhisa Komatsu, Naoki H. Kumagai, Hiroomi Miyamoto, Kazushi Miyashita, Haruyuki Morimoto, Ryota Nakajima, Shuhei Nishida, Kou Nishiuchi, Shingo Sakamoto, Masayoshi Sano, Kenji Sudo, Hiroya Sugisaki, Kazuaki Tadokoro, Katsuhiko Tanaka, Yoshie Jintsu-Uchifune, Kentaro Watanabe, Hiromi Watanabe, Yumiko Yara, Norishige Yotsukura, Yoshihisa Shirayama
    MARINE POLICY 51 136 - 147 2015年01月 [査読有り][通常論文]
     
    After the adoption of the Aichi Target, data accumulation and evaluation regarding biodiversity have progressed rapidly. The use of ecologically and biologically significant areas (EBSAs) criteria to evaluate important areas enables the identification of effective and prioritized areas for ecosystem management. This includes strategic environmental assessment and discussions aimed at establishing protected marine areas based on scientific data. This paper reviews previous and current ideas as well as the methods used, for the identification of EBSAs. In particular, the following issues are addressed: problems associated with different types of marine ecosystems in the Japanese Archipelago, such as seagrass and seaweed beds, coral reefs, offshore pelagic plankton, and deep-sea benthic ecosystems; and problems associated with the integration of multiple criteria that are not totally exclusive. Several candidate variables accounting for each of the 7 criteria used to identify ecologically important areas are presented. Data availability is the most important criterion that allowed for the comprehensive evaluation of different types of ecosystems in the same localities. In particular, for coastal ecosystems such as seagrass, seaweed beds, and coral reefs, it is possible to carry out broad spatial comparisons using variables representing most of these 7 criteria. Regarding methods for the quantitative evaluation of each criterion and their integration, application of these methods to kelp forest ecosystems in Hokkaido, Northern Japan is presented as a case study. (C) 2014 The Authors. Published by Elsevier Ltd.
  • Kentaro Honda, Wilfredo H. Uy, Darwin I. Baslot, Allyn Duvin S. Pantallano, Yohei Nakamura, Masahiro Nakaoka
    AQUATIC BIOLOGY 24 3 163 - 174 2015年 [査読有り][通常論文]
     
    The diel habitat-use patterns of commercially important fishes in a small marine protected area (MPA) (0.31 km(2)) containing coral reef and seagrass habitats were examined by passive acoustic telemetry during 2011 and 2012. The occurrence patterns of the target fishes both inside and outside the MPA were also observed. Thirty individuals from 6 species (20.2 to 41.4 cm fork length) were caught, acoustically tagged and released inside the MPA, and 4 to 210 d of tracking data were then obtained from 28 detected fishes. Lutjanus monostigma, Lethrinus atkinsoni, and Lethrinus obsoletus were found to mostly inhabit the coral reef. The remaining 3 species (Lutjanus argentimaculatus, Lethrinus harak, and Siganus guttatus) utilized both coral and seagrass habitats but showed different patterns: Lutjanus argentimaculatus visited seagrass only at night; Lethrinus harak occurred in the coral reef more at night than in the day, showing the opposite pattern in seagrass; and S. guttatus exhibited the converse pattern to L. harak. More than one-third of the tracked individuals moved inside and outside the MPA more than once per day on average during the tracking period. However, 95.4% of detections were recorded by acoustic receivers deployed inside the MPA. Underwater visual surveys revealed that the densities of some target fishes were significantly higher inside than outside the MPA. These findings suggest that the MPA protects the core of fish home ranges.
  • Yuichi Nakajima, Yu Matsuki, Chunlan Lian, Miguel D. Fortes, Wilfredo H. Uy, Wilfredo L. Campos, Masahiro Nakaoka, Kazuo Nadaoka
    MOLECULAR ECOLOGY 23 24 6029 - 6044 2014年12月 [査読有り][通常論文]
     
    Information on genetic diversity and differentiation of seagrass populations is essential for the conservation of coastal ecosystems. However, little is known about the seagrasses in the Indo-West Pacific Ocean, where the world's highest diversity of seagrasses occurs. The influence of sea currents on these populations is also unknown. We estimated the genetic diversity and population genetic structure and identified reproductive features in Enhalus acoroides populations from the Yaeyama Islands, Hainan Island and the Philippines. The Philippines are situated at the centre of the E.acoroides range, Yaeyama and Hainan are peripheral populations, and the Yaeyama population is at the northern limit of the species range. The powerful Kuroshio Current flows from the Philippines to Yaeyama. Genetic analyses using nine microsatellite markers indicated that reproduction of E.acoroides is mostly sexual. Clonal diversity does not decrease in northern populations, although genetic diversity does. However, the genetic diversity of the Yaeyama populations is greater than that of the Hainan populations. Significant genetic differentiation among most populations was evident; however, the Yaeyama and north-east Philippines populations were genetically similar, despite being separated by similar to 1100km. An assignment test suggested that recruitment occurs from the north-east Philippines to Yaeyama. The strong current in this region is probably responsible for the extant genetic diversity and recruitment patterns.
  • Katsumasa Yamada, Yoshiyuki Tanaka, Takuya Era, Masahiro Nakaoka
    GLOBAL ECOLOGY AND CONSERVATION 2 47 - 61 2014年12月 [査読有り][通常論文]
     
    The relative contributions of environmental and spatial processes in macroinvertebrate community structure (i.e., beta-diversity) for three functional groups classified on the basis of dispersal ability and microhabitat selection (seagrass-associated [SA], drift-faunal [DF], and benthic-faunal [BF] groups) were examined in a seagrass ecosystem along the Sanriku coast of Japan. Variation partitioning was conducted to explain the environmental heterogeneity and spatial arrangement of local communities (i.e., degree of variation in the community) for each functional group. Processes determining community structure and metacommunity type differed among the functional groups. The SA group was under greater influence of environmental control, whereas the fractions of beta-diversity in the DF and BF groups were explained by only spatial predictors. Thus, even if macroinvertebrate communities live in the same ecosystem, different mechanisms may determine the functional community structure, which depends on ecological traits such as dispersal ability and microhabitat. Ecological processes underlying community assembly differ among functional groups, indicating that the existence and/or dynamics of seagrass patches may affect the variation of faunal functions in an ecosystem. (C) 2014 The Authors. Published by Elsevier B.V.
  • Keiichi Fukaya, Takehiro Okuda, Masahiro Nakaoka, Takashi Noda
    JOURNAL OF ANIMAL ECOLOGY 83 6 1334 - 1343 2014年11月 [査読有り][通常論文]
     
    Explanations for why population dynamics vary across the range of a species reflect two contrasting hypotheses: (i) temporal variability of populations is larger in the centre of the range compared to the margins because overcompensatory density dependence destabilizes population dynamics and (ii) population variability is larger near the margins, where populations are more susceptible to environmental fluctuations. In both of these hypotheses, positions within the range are assumed to affect population variability. In contrast, the fact that population variability is often related to mean population size implies that the spatial structure of the population size within the range of a species may also be a useful predictor of the spatial variation in temporal variability of population size over the range of the species. To explore how population temporal variability varies spatially and the underlying processes responsible for the spatial variation, we focused on the intertidal barnacle Chthamalus dalli and examined differences in its population dynamics along the tidal levels it inhabits. Changes in coverage of barnacle populations were monitored for 105years at 25 plots spanning the elevational range of this species. Data were analysed by fitting a population dynamics model to estimate the effects of density-dependent and density-independent processes on population growth. We also examined the temporal mean-variance relationship of population size with parameters estimated from the population dynamics model. We found that the relative variability of populations tended to increase from the centre of the elevational range towards the margins because of an increase in the magnitude of stochastic fluctuations of growth rates. Thus, our results supported hypothesis (2). We also found that spatial variations in temporal population variability were well characterized by Taylor's power law, the relative population variability being inversely related to the mean population size. Results suggest that understanding the population dynamics of a species over its range may be facilitated by taking the spatial structure of population size into account as well as by considering changes in population processes as a function of position within the range of the species.
  • Yoshiyuki Tanaka, Gay Amabelle Go, Atsushi Watanabe, Toshihiro Miyajima, Masahiro Nakaoka, Wilfredo H. Uy, Kazuo Nadaoka, Shuichi Watanabe, Miguel D. Fortes
    MARINE POLLUTION BULLETIN 88 1-2 81 - 85 2014年11月 [査読有り][通常論文]
     
    Effects of fish culture can alter the adjacent ecosystems. This study compared seagrass species compositions in 2012 with those in 1995, when fish culture was less intensive compared to 2012 in the region. Observations were conducted at the same four sites around Santiago Island, Bolinao: (1) Silaqui Island, (2) Binaballian Loob, (3) Pislatan and (4) Santa Barbara, and by using the same methods as those of Bach et al. (1998). These sites were originally selected along a siltation gradient, ranging from Site 1, the most pristine, to Site 4, a heavily silted site. By 2012, fish culture had expanded around Sites 2,3 and 4, where chlorophyll a (Chl a) was greater in 2012 than in 1995 by one order of magnitude. Enhalus acoroides and Cymodocea serrulata, which were recorded in 1995, were no longer present at Site 4, where both siltation and nutrient load are heavy. (C) 2014 Elsevier Ltd. All rights reserved.
  • Masaaki Sato, Hiroyuki Kurokochi, Engkong Tan, Shuichi Asakawa, Kentaro Honda, Klenthon O. Bolisay, Yohei Nakamura, Chunlan Lian, Miguel D. Fortes, Masahiro Nakaoka
    CONSERVATION GENETICS RESOURCES 6 3 685 - 688 2014年09月 [査読有り][通常論文]
     
    Anemonefishes are popular model species for research on population connectivity via larval dispersal, and understanding this connectivity is beneficial when designing marine protected areas. We developed 15 microsatellite markers for two anemonefishes, Amphiprion frenatus and Amphiprion perideraion. Of these 15 markers, 10 worked well for both species, while three were specific for A. frenatus and two were specific for A. perideraion. For A. frenatus, the number of alleles at each locus ranged from 4 to 28, and the observed and expected heterozygosities ranged from 0.258 to 0.938 and from 0.285 to 0.953, respectively. For A. perideraion, the respective numbers were 4-14, 0.344-0.969, and 0.412-0.868. These microsatellite markers will be useful for the study of population connectivity in these two species.
  • A. K. M. Rashidul Alam, Tomoaki Hagino, Keiichi Fukaya, Takehiro Okuda, Masahiro Nakaoka, Takashi Noda
    BIOLOGICAL INVASIONS 16 8 1699 - 1708 2014年08月 [査読有り][通常論文]
     
    To understand the patterns and processes associated with the population dynamics of Balanus glandula during the early phase of invasion along the Pacific coast of eastern Hokkaido, population surveys were conducted from 2002 to 2011 at five shores, each consisting of five paired plots (scraped recruitment plot and unscraped establishment plot), along 49 km of coastline located 144 km east of the eastern front of the invasion of this species in 2000. Larval recruitment was first detected in 2004, but the establishment of a population was not observed until 2 years later at the westernmost shore of the study area. Occurrence increased from non-native barnacle present in 4 % of plots in 2006 to 100 % in 2011, but mean coverage remained low (< 5 %) in 2011. Most local population coverage fluctuated without indicating clear temporal trends, but coverage in one plot showed a consistent pattern of rapid increase. Local extinctions occurred, but rates of local extinction decreased with time as larval recruitment increased. Lag times between recruitment and establishment occurred for 64 % of the paired plots and ranged from 1 to 4 years. Lag times decreased after 5 years, when larval recruitment increased. These findings suggest that the intensity of larval recruitment determined invasion dynamics during this early phase of the invasion, and the monitoring of recruitment is therefore essential for early detection of invasions by sessile marine organisms and prediction of their range expansion.
  • Venus Leopardas, Wilfredo Uy, Masahiro Nakaoka
    JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 457 71 - 80 2014年08月 [査読有り][通常論文]
     
    Although the influence of seagrasses on the diversity and abundance of associated fauna is generally well understood, the effects of seagrass specific identity are not. To determine whether benthic epifaunal and infaunal assemblage patterns vary by the identity of dominant seagrass species in shallow water meadows, we compared quantitative measures of faunal species richness, abundance, and assemblage structure among beds dominated by Cymodocea rotundata, Enhalus acoroides, and Thalassia hemprichii the study site was at Lopez Jaena, Misamis Occidental Province in the southern Philippines. The Cymodocea-dominated vegetation had higher seagrass shoot density and lower seagrass biomass than those dominated by Enhalus and Thalassia. Across vegetation types, we encountered 30 and 15 species of epifauna and infauna at average densities of 1.73 and 0.82 animals/core (0.0314 m(2)), respectively. Neither densities and species richnesses of epifauna and infauna nor species composition varied significantly by vegetation type. Multivariate analyses of macrofaunal assemblage structure and abiotic/biotic environmental factors demonstrated that seagrass aboveground biomass explained a significant proportion of the multivariate variation in epifaunal species composition (39%); none of the potential explanatory variables was related to variation in ecological parameters of the infauna. Thus, seagrass specific identity is not a good predictor of either macrofaunal abundance or diversity patterns. Although the ecological parameters of the benthic macrofauna may be influenced by seagrass biomass and structure, responses differ between epifauna and infauna. (C) 2014 Elsevier B.V. All rights reserved.
  • Masaaki Sato, Kentaro Honda, Klenthon O. Bolisay, Yohei Nakamura, Miguel D. Fortes, Masahiro Nakaoka
    HYDROBIOLOGIA 733 1 63 - 69 2014年07月 [査読有り][通常論文]
     
    Many marine organisms disperse or migrate among habitats, which affects their abundance patterns at individual local habitats. To clarify the factors affecting the distribution patterns of two anemonefishes (Amphiprion frenatus and A. perideraion), we measured the habitat patch size (anemone size), patch isolation (mean distance from other anemones), presence/absence of other anemonefish species, depth, and abundance of the two anemonefishes at each anemone around a semi-closed bay (up to 3.7 km) in Puerto Galera, the Philippines. We assumed that local abundance increases with habitat size and decreases with patch isolation because of greater resource availability and reduced rates of recruitment from other patches. Local abundance of A. frenatus was related to habitat size and the presence of other anemonefish species, whereas that of A. perideraion was affected by the presence of other anemonefish species and water depth. Interspecific competition and/or niche differentiation of habitat can explain the negative relationship between the local abundance of the target species and other anemonefish. Patch isolation was not significant for both species probably because the dispersal rate was not directly proportional to the geographic distance between patches at our study site.
  • Dan M. Arriesgado, Yuichi Nakajima, Yu Matsuki, Chunlan Lian, Satoshi Nagai, Motoshige Yasuike, Yoji Nakamura, Miguel D. Fortes, Wilfredo H. Uy, Wilfredo L. Campos, Masahiro Nakaoka, Kazuo Nadaoka
    CONSERVATION GENETICS RESOURCES 6 1 135 - 138 2014年03月 [査読有り][通常論文]
     
    Genetic diversity and population genetic structure are key components of seagrass resilience and contribute to an understanding of its conservation and management. We isolated 29 polymorphic microsatellite (SSR) markers from a widely distributed pioneer seagrass, Cymodocea rotundata, by two methods; next generation sequencing and compound SSR marker isolation. Twenty-nine markers had 2-14 alleles per locus, and the observed and expected heterozygosity ranged from 0 to 0.688, and 0.113 to 0.770, respectively. These loci will facilitate investigation of the genetic diversity and population genetic connectivity and structure of C. rotundata.
  • Yu Matsuki, Akiko Takahashi, Yuichi Nakajima, Chunlan Lian, Miguel D. Fortes, Wilfredo H. Uy, Wilfredo L. Campos, Masahiro Nakaoka, Kazuo Nadaoka
    CONSERVATION GENETICS RESOURCES 5 3 715 - 717 2013年09月 [査読有り][通常論文]
     
    Nine microsatellite markers of a tropical seagrass species, Syringodium isoetifolium, were developed to investigate genetic diversity and genetic connectivity. The number of alleles detected per locus ranged from two to 16, and the observed and expected heterozygosities ranged from 0.00 to 1.00 and 0.12 to 0.91, respectively. The markers described here are sufficiently polymorphic and informative to investigate the genetic diversity, genetic connectivity and genetic structure of S. isoetifolium.
  • Yuichi Nakajima, Nina Yasuda, Yu Matsuki, Dan M. Arriesgado, Chunlan Lian, Miguel D. Fortes, Wilfredo H. Uy, Wilfredo L. Campos, Masahiro Nakaoka, Coralie Taquet, Suharsono, Satoshi Nagai, Kazuo Nadaoka
    MARINE GENOMICS 11 27 - 29 2013年09月 [査読有り][通常論文]
     
    Ten novel polymorphic nuclear microsatellite simple sequence repeat (SSR) markers were isolated from an Indo-Pacific horned starfish, Protoreaster nodosus. The isolated SSR markers provided polymorphisms of 2-9 alleles per locus in three populations obtained from Indonesia and the Philippines. The expected and observed heterozygosities ranged from 0.049 to 0.691 and from 0.050 to 0.800, respectively. Pairwise F5,values among three populations ranged from 0.018 to 0.050 (global F-ST = 0.031). All P. nodosus individuals collected from three populations exhibited different genotypes for the ten identified SSR markers, indicating that P. nodosus reproduces sexually. Then the developed SSR markers will be useful for studying the population and conservation genetics of P. nodosus. (C) 2013 Elsevier B.V. All rights reserved.
  • Kentaro Honda, Yohei Nakamura, Masahiro Nakaoka, Wilfredo H. Uy, Miguel D. Fortes
    PLOS ONE 8 8 2013年08月 [査読有り][通常論文]
     
    Understanding the interconnectivity of organisms among different habitats is a key requirement for generating effective management plans in coastal ecosystems, particularly when determining component habitat structures in marine protected areas. To elucidate the patterns of habitat use by fishes among coral, seagrass, and mangrove habitats, and between natural and transplanted mangroves, visual censuses were conducted semiannually at two sites in the Philippines during September and March 2010-2012. In total, 265 species and 15,930 individuals were recorded. Species richness and abundance of fishes were significantly higher in coral reefs (234 species, 12,306 individuals) than in seagrass (38 species, 1,198 individuals) and mangrove (47 species, 2,426 individuals) habitats. Similarity tests revealed a highly significant difference among the three habitats. Fishes exhibited two different strategies for habitat use, inhabiting either a single (85.6% of recorded species) or several habitats (14.4%). Some fish that utilized multiple habitats, such as Lutjanus monostigma and Parupeneus barberinus, showed possible ontogenetic habitat shifts from mangroves and/or seagrass habitats to coral reefs. Moreover, over 20% of commercial fish species used multiple habitats, highlighting the importance of including different habitat types within marine protected areas to achieve efficient and effective resource management. Neither species richness nor abundance of fishes significantly differed between natural and transplanted mangroves. In addition, 14 fish species were recorded in a 20-year-old transplanted mangrove area, and over 90% of these species used multiple habitats, further demonstrating the key role of transplanted mangroves as a reef fish habitat in this region.
  • Keiichi Fukaya, Takehiro Okuda, Masakazu Hori, Tomoko Yamamoto, Masahiro Nakaoka, Takashi Noda
    ECOSPHERE 4 4 art48  2013年04月 [査読有り][通常論文]
     
    Although researchers recognize that population dynamics can vary in space and time as a result of differences in biotic and abiotic conditions, spatial and temporal variability in the patterns and processes of population dynamics have not been well documented on a seasonal time frame. We quantified seasonal changes in the coverage of intertidal barnacles, Chthamalus spp., with data collected for as many as 9 years at 88 plots in five regions located along more than 1800 km of the Pacific coastline of Japan from 31 degrees N to 43 degrees N. To examine how seasonal changes and the spatial heterogeneity of environments can interact to influence patterns and processes of population dynamics, we analyzed the data with two models of population variability: a population dynamics model, which provides knowledge about processes that determine population growth rates; and Taylor's power law, which summarizes the relationship between the temporal mean and variance of the size of a population (temporal mean-variance relationship). We found that seasonal differences were prevalent in population growth rates, as well as in the strength and spatial scales of processes that determine population growth rates. In addition, the seasonality of these rates and processes varied between habitats at different spatial scales ranging from the scale of among-rocks within a shore to that of among-regions located in different latitudes, suggesting that the effects of seasonal environmental fluctuations on population growth can depend on the spatial heterogeneity of biotic and abiotic conditions that vary at multiple spatial scales. In contrast, the evidence for spatiotemporal differences in temporal mean-variance relationships was weak. Unlike theoretical expectations, spatiotemporal differences in the variability of population size were best explained by a unique power law, despite remarkable regional and seasonal differences in the processes that determine population growth rates. These results suggest that spatiotemporal environmental variability can affect population dynamics at multiple spatial scales but do not necessarily alter the scaling law of population size variability.
  • Takashi Maeda, Tadashi Kawai, Masahiro Nakaoka, Norishige Yotsukura
    JOURNAL OF APPLIED PHYCOLOGY 25 1 337 - 347 2013年02月 [査読有り][通常論文]
     
    Deoxyribonucleic acid (DNA) fragment analysis can become an effective tool to study genetic differences between species and individuals on saccharinan kelp from which the little genetic diversity has been reported. Here, extraction methods of DNA suitable for use in analysis with a capillary sequencer is examined on Saccharina japonica var. diabolica which contains abundant polysaccharide. When amplified fragment length polymorphism was performed using genomic DNA extracted by seven different methods: (1) commercial kit, (2) original cetyl trimethylammonium bromide (CTAB) method, (3)-(5) three types of modified CTAB method, (6) modified sodium dodecyl sulfate (SDS) method, (7) combination of CTAB method and SDS method, a high reproducible peak that was suitable for analysis was noticeable in the electropherogram in the experiment with the last combination method (7). It is considered that the pretreatment washing of polysaccharide and the subsequent purification for protein and ribonucleic acid in SDS method and for polysaccharide in CTAB method are effective to obtain the high-purity DNA.
  • Yu Matsuki, Yuichi Nakajima, Chunlan Lian, Miguel D. Fortes, Wilfredo H. Uy, Wilfredo L. Campos, Masahiro Nakaoka, Kazuo Nadaoka
    CONSERVATION GENETICS RESOURCES 4 4 1007 - 1010 2012年12月 [査読有り][通常論文]
     
    Nine microsatellite markers of a widely-distributed seagrass, Thalassia hemprichii, were developed to investigate genetic diversity and genetic connectivity. The number of alleles detected per locus ranged from 3 to 26, and the expected and observed heterozygosities ranged from 0.00 to 1.00 and 0.00 to 0.87, respectively. The markers described here are sufficiently polymorphic and informative to investigate the genetic diversity, genetic connectivity and genetic structure of T. hemprichii.
  • Yuichi Nakajima, Yu Matsuki, Chunlan Lian, Miguel D. Fortes, Wilfredo H. Uy, Wilfredo L. Campos, Masahiro Nakaoka, Kazuo Nadaoka
    CONSERVATION GENETICS RESOURCES 4 2 515 - 517 2012年06月 [査読有り][通常論文]
     
    Using the dual-suppression polymerase chain reaction technique, 12 novel polymorphic nuclear microsatellite DNA markers were isolated from the tropical seagrass Enhalus acoroides. The isolated markers provided the polymorphisms of 2-13 alleles per locus in 3 populations located in Japan, China, and the Philippines. The values of the expected heterozygosity fell in the following ranges: 0.000-0.693 (Japan), 0.000-0.623 (China), and 0.000-0.765 (Philippines). Compared to the Philippines population (1 monomorphic locus), a relatively higher proportion of the SSR loci did not show polymorphism in the marginal habitats of E. acoroides (5 loci in Japan; 5 loci in China). These markers may be useful for population and conservation genetics of E. acoroides.
  • Genetic diversity and gene flow of East Asian seagrass, Zostera caespitosa Miki (Zosteraceae), in northeast Japan
    Tanaka, N, Nakaoka, M, Omori, Y, Aioi, K
    Bulletin of the National Museum of Nature and Science. Series B 38 29 - 36 2012年03月 [査読有り]
  • SHIMABUKURO HIROMORI, HORI MASAKAZU, YOSHIMITSU SATOSHI, TOKUNAGA NARIMITSU, IGARI TADAMITSU, SASAKI KENSUKE, NAKAOKA MASAHIRO, KAWANE MASAKO, YOSHIDA GORO, HAMAGUCHI MASAMI
    NIPPON SUISAN GAKKAISHI 78 2 204 - 211 Japanese Society of Fisheries Science 2012年 [査読有り]
  • Fortes, M. D, Go, G. A, Bolisay, K, Nakaoka, M, Uy, W. H, Lopez, M. R, Leopardas, V, Leriorato, J, Allyn Pantallano, A, Paciencia Jr., F, Watai, M, Honda, K, Edralin, M
    Proceedings of the 12th International Coral Reef Symposium, Cairns, Australia, 9-13 July 2012, ICRS2012_15B_3 2012年 [査読有り][通常論文]
  • Kyoda, J, Hosokawa, S, Watanabe, K, Nakaoka, M, Shibanuma, S, Montani, S, Kuwae,T
    Journal of Hydraulic, Coastal and Environmental Engineering 68 2 1466 - 1470 2012年 [査読有り][通常論文]
  • Kamauchi, H, Sato, S, Hayashi, D, Okabe, Y, Katsuyama, T, Fukushima, K, Yoshioka, A, Sato, T, Tokuchi, N, Nakaoka, M
    Forest Research 78 78 81 - 87 京都大学フィールド科学教育研究センター森林生物圏部門 2012年 [査読有り][通常論文]
     
    高緯度域では遡河性魚類によって河川に輸送される海洋由来栄養塩 (Marine derived nutrient : MDN)が河川内および河畔域の生物群集に影響を与えているとされる. 本研究では北海道東部の森林河川上流部において初冬にシロザケ死骸 (ホッチャレ)を約800kg 散布し, ホッチャレの消費者を明らかにした. 散布した死骸は10日間でほとんどすべて消費された. 自動撮影された画像から, 消費者はカラス類が優占しており, トビおよびオオワシを含めて鳥類が96% を占めた. カラス類は近隣の牧場で越冬している個体が移動したと思われた. 自動撮影された画像では, カラス類の摂食は少なくともホッチャレの一部が水面上に露出した場合に限られていたのに対して, オオワシは水面下のホッチャレも摂食した. 集水域の周囲の土地利用や河川の水深および河道形状がホッチャレの消費者組成に影響することが示唆された. 鳥類は, 秋にMDN を輸送するクマとは行動範囲や摂食パターンが異なるため, 初冬にシロザケが遡上する河川では, MDNの散布距離や散布量が秋とは異なることが考えられる.Marine derived nutrient (MDN), which is carried to stream by anadromous animals, affects stream and riparian ecosystems at high latitudes. To clarify the consumer of salmon carcasses during early winter of Eastern Hokkaido, we carried out a field experiment on spreading out carcasses (ca. 800 kg) at a woodland stream. Almost all of carcasses were consumed during 10 days. Crows was dominant, and birds abundance including black kite and Steller's sea eagle occupied 96 % of photo-trapping data. Crows were thought as immigrant from ranches surrounding experimental watershed. From the photo-trapping data, although crows fed only if, at least, a part of carcass was exposed over the water surface, Steller's sea eagle fed carcass even if it submerged. It suggests that land use of surrounding the watershed, channel morphology or depth of stream would affect the composition of carcasses consumer. Because of unique behavior (e.g. migration distance, feeding pattern) by bird, spreading distance and amount of MDN would show different pattern against autumn in streams that salmon runs in early winter.
  • Takehisa Yamakita, Kentaro Watanabe, Masahiro Nakaoka
    ECOGRAPHY 34 3 519 - 528 2011年06月 [査読有り][通常論文]
     
    It is known that asynchronous temporal variations in local populations can contribute to the stability of metapopulations. However, studies evaluating the hierarchical organization of multiple spatial scales are rare for continuous marine landscapes, especially for marine vegetation such as seagrass beds. In this study, long-term observation (26 yr) of temporal changes and nested spatial analyses were combined for an extensive seagrass meadow in Tokyo Bay, Japan, using remote sensing and geographic information system technologies. We examined how the dynamics at the whole-bed scale (similar to 1 km2) are related to those at a local scale (0.04 km2), and investigated the relationship between the seagrass dynamics and long-term changes in environmental conditions using data on oceanography, water quality, and sediment dynamics. The seagrass bed size fluctuated between a maximum of 1.28 km2 (in 1987) and a minimum of 0.39 km2 (in 2001), with an average of 0.90 km2. The temporal variation in seagrass bed size at the whole-bed scale correlated with sand movement within the seagrass bed related to changes in the position of a sandbar. Seagrass bed size fluctuated asynchronously at a local scale. Multivariate analyses recognized clusters of local areas showing similar patterns of fluctuation. Temporal patterns in the various clusters responded differently to changes in environmental factors, e.g. the position of the sandbar was highly correlated with seagrass bed size in shallow habitats but not in deeper areas. The magnitudes of the temporal variations for the local clusters were greater than that of the entire bed, suggesting that asynchronous fluctuation in different areas of the bed plays an important role in the overall stability of the seagrass bed. The results of the present study also highlight the importance of physical processes in regulating the temporal dynamics of seagrass beds in shallow sedimentary landscapes.
  • Martin Wahl, Heike Link, Nicolaos Alexandridis, Jeremy C. Thomason, Mauricio Cifuentes, Mark J. Costello, Bernardo A. P. da Gama, Kristina Hillock, Alistair J. Hobday, Manfred J. Kaufmann, Stefanie Keller, Patrik Kraufvelin, Ina Kruger, Lars Lauterbach, Bruno L. Antunes, Markus Molis, Masahiro Nakaoka, Julia Nystrom, Zulkamal bin Radzi, Bjoern Stockhausen, Martin Thiel, Thomas Vance, Annika Weseloh, Mark Whittle, Lisa Wiesmann, Laura Wunderer, Takehisa Yamakita, Mark Lenz
    PLOS ONE 6 5 2011年05月 [査読有り][通常論文]
     
    Species richness is the most commonly used but controversial biodiversity metric in studies on aspects of community stability such as structural composition or productivity. The apparent ambiguity of theoretical and experimental findings may in part be due to experimental shortcomings and/or heterogeneity of scales and methods in earlier studies. This has led to an urgent call for improved and more realistic experiments. In a series of experiments replicated at a global scale we translocated several hundred marine hard bottom communities to new environments simulating a rapid but moderate environmental change. Subsequently, we measured their rate of compositional change (re-structuring) which in the great majority of cases represented a compositional convergence towards local communities. Re-structuring is driven by mortality of community components (original species) and establishment of new species in the changed environmental context. The rate of this re-structuring was then related to various system properties. We show that availability of free substratum relates negatively while taxon richness relates positively to structural persistence (i.e., no or slow re-structuring). Thus, when faced with environmental change, taxon-rich communities retain their original composition longer than taxon-poor communities. The effect of taxon richness, however, interacts with another aspect of diversity, functional richness. Indeed, taxon richness relates positively to persistence in functionally depauperate communities, but not in functionally diverse communities. The interaction between taxonomic and functional diversity with regard to the behaviour of communities exposed to environmental stress may help understand some of the seemingly contrasting findings of past research.
  • Norio Tanaka, Teruko Demise, Mitsuhiro Ishii, Yasumasa Shoji, Masahiro Nakaoka
    Marine Biology 158 4 871 - 882 2011年04月 [査読有り][通常論文]
     
    Massive losses of eelgrass Zostera marina beds in Japan have occurred over the past 100 years. Toward their restoration, transplantation of eelgrass has been attempted in some areas, including Tokyo Bay. This study examined population genetic structures and gene flow in eelgrass in Tokyo Bay to establish guidelines for conducting restoration. Genotypes of a total of 360 individuals from 12 beds were determined using five microsatellite markers. The eelgrass beds in inner bay had above-average genetic diversity. A neighbor-joining tree based on F-ST values among beds revealed that a strong gene flow had occurred among six beds in the inner bay. Genetic assignment testing of drifting shoots indicated that those with seeds migrate in both directions between the inner and outer bay. We suggested that the restoration of eelgrass in the innermost part of Tokyo Bay, where natural habitats have been lost, should be conducted using the inner bay beds.
  • Andreas Kubicek, Kazuhiro Bessho, Masahiro Nakaoka, Martin Wahl, Mark Lenz
    JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 397 2 208 - 213 2011年02月 [査読有り][通常論文]
     
    Among the numerous anti-herbivore defences developed by macroalgae, chemical and morphological traits are best documented and understood. Plant defence theory suggests that these resistances, which can either be constitutive or inducible, are associated with metabolic costs. They should therefore be impaired under conditions of energy limitation, but evidence for this prediction is scarce. In two subsequent experiments, we tested whether a reduction of light availability is changing feeding rates of the two mesoherbivores Idotea ochotensis and Lacuna smithii on the red alga Chondrus yendoi. Algal individuals were kept in outdoor mesocosm facilities for 10 days, during which we manipulated the amount of incoming sunlight at 6 levels (0%-99% reduction. i.e. 2000-20 mu mol s(-1) m(-2)). Orthogonal to this, we established the presence or absence of one of the herbivores to test whether C yendoi can generate a defence. Algal palatability was investigated afterwards in no-choice feeding assays using naive grazer individuals. The consumption of algal tissue in L smithii increased with decreasing light, while this was not the case for I. ochotensis. However, we found a defence induced as a reaction to herbivory only by the highly mobile isopod but not when the slowly moving snail grazed on C. yendoi. Isopod total consumption rates in our experiments were 40 times higher than those of the gastropods. We therefore suggest that C yendoi exhibits grazer-specific reactions to herbivory, depending on the mobility and voracity of the consumers. Interestingly, only for one of the grazers, i.e. the snail, short-term light reduction influenced the palatability of algal tissue. We discuss different but not mutually exclusive models that could explain this pattern. In conclusion, we view this three-species system as an illustrative example for specificity in grazer-algal interactions and their modification by environmental stress. (C) 2010 Elsevier B.V. All rights reserved.
  • Takehisa Yamakita, Masahiro Nakaoka
    INTERNATIONAL CONFERENCE: SPATIAL THINKING AND GEOGRAPHIC INFORMATION SCIENCES 2011 21 177 - 183 2011年 [査読有り][通常論文]
     
    The term scale has been used in many ways. In continuous landscape analysis, the spatial scale consists of two components; grain and extent. Most previous studies on the scale issue were conducted in limited range or on one component of the scale. To further step up, we compared theory of scaling by applying indices developed for terrestrial static landscape to underwater vegetation. The result suggested that changing grain shows power-low scaling relationships for the most of landscape indices. Changing extent increased variation of above scaling relationships. We conclude that changing both components reveal the possibility to extrapolate these indices into different scales or places. For the conservation of ecosystems, recognition of scaling relationships is necessary to build more spatially explicit planning and understanding of phenomenon. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Yasushi Asami
  • Yamada K, Hori M, Nakaoka M, Hamaguchi M
    Crustaceana Monographs 15 325 - 339 2011年 [査読有り][通常論文]
  • Hiroshi Adachi, Hiroya Yamano, Toshihiro Miyajima, Masahiro Nakaoka
    JOURNAL OF OCEANOGRAPHY 66 6 865 - 872 2010年12月 [査読有り][通常論文]
     
    This article describes a simple, quick, and inexpensive procedure for coring unconsolidated sediment in shallow water (< 30 m from water surface). A similar to 1 m core is retrieved by a PVC pipe that penetrates sediment in response to the percussive force of a hand-operated hammering tool or air hammer. After retrieving the first core segment, a casing is inserted to allow access to deeper sediment layers. Pulverized sediment produced during coring is removed by a water-lubrication system that is powered by an electric pump attached to a generator. Using this system and procedure, five 2-m-long cores with excellent quality were retrieved.
  • Keiichi Fukaya, Takehiro Okuda, Masahiro Nakaoka, Masakazu Hori, Takashi Noda
    JOURNAL OF ANIMAL ECOLOGY 79 6 1270 - 1279 2010年11月 [査読有り][通常論文]
     
    P>1. Population growth rate is determined by both density-dependent and density-independent processes. In the temperate zone, the strength and spatial scale of these processes are likely to differ seasonally, but such differences have rarely been quantitatively examined. 2. Coverage, the area occupied by organisms, is a measure of resource use in sessile marine populations. Population models used for density-based studies should be able to characterize effectively fluctuations in coverage, but few have tried to apply such models to sessile populations. 3. We observed coverage of the intertidal barnacle Chthamalus challengeri at 20 plots on four shores along the Pacific coast of Japan over 8 years. We then fitted a population model that incorporated both a density-dependent process (strength of density dependence) and density-independent processes (intrinsic growth rate and stochastic fluctuation at different spatial scales) to these data to analyse the seasonal variation of these processes and answer the following two questions: (i) How do the effects of density-dependent and density-independent processes on population growth vary seasonally? (ii) At what spatial scale, regional (tens of kilometres), shore (hundreds of metres), or rock (tens of centimetres), does density-independent stochastic fluctuation most strongly affect population size changes? 4. Barnacle population size tended to decrease in summer, when population dynamics were characterized by a relatively lower intrinsic growth rate, weaker density dependence and stronger stochastic fluctuation. In contrast, population size tended to increase in winter, reflecting a higher intrinsic growth rate, strong density dependence and weak stochastic fluctuation. 5. In summer, population growth rate was strongly affected by regional-scale stochastic fluctuation, whereas in winter it was affected more by rock-scale stochastic fluctuation, suggesting that populations were strongly affected by regional-scale processes in summer but not in winter. 6. These results indicate that seasonally variable density-dependent and density-independent processes determine the population dynamics of C. challengeri. Therefore, to understand fluctuation patterns of populations of this species, seasonality should be taken into account. Moreover, this study demonstrates that population models commonly used for density-based studies are also applicable to coverage-based population studies.
  • Takehiro Okuda, Takashi Noda, Tomoko Yamamoto, Masakazu Hori, Masahiro Nakaoka
    ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 36 4 413 - 422 2010年07月 [査読有り][通常論文]
     
    It has been debated whether the community structure of an open system is more dependent on environmental processes associated with niche explanations, or on spatial processes related to dispersal Their relative importance may differ among taxonomic groups with properties of the community such as ecological characteristics (e g, dispersal ability and life history) and habitat type We examined the relative importance of environmental and spatial processes on community structure for three taxonomic groups with different ecological characteristics (macroalgae, sessile invertebrates, and mobile molluscs) in rocky intertidal shores of Sanriku Coast, Japan. To evaluate the relative contribution of the two processes in determining community structure, we conducted variation partitioning to reveal the degree of variation of community structure (ie, beta-diversity) explained by environmental heterogeneity and spatial arrangement of local communities The results of our analyses indicated that beta-diversity was significantly explained by both environmental factors (macroalgae, 29.3% of community variation sessile animal, 407%. mobile molluscs, 16.7%) and spatial factors (macroalgae, 19.9% sessile animal, 3 6%: mobile molluscs, 6 6%) in all taxonomic groups These results imply that although some taxonomic groups live in the same ecosystem, share common resources, and interact with each other, the mechanisms determining their community structure change depending on ecological characteristics such as dispersal ability and life history (c) 2010 Elsevier Masson SAS All rights reserved
  • Napakhwan Whanpetch, Masahiro Nakaoka, Hiroshi Mukai, Takao Suzuki, Satoshi Nojima, Takashi Kawai, Chittima Aryuthaka
    ESTUARINE COASTAL AND SHELF SCIENCE 87 2 246 - 252 2010年04月 [査読有り][通常論文]
     
    Seagrass beds are susceptible to various natural and human-induced disturbances. Disturbances affect not only seagrasses, but also the abundance and diversity of associated macrofaunal communities. The Andaman Sea coast of Thailand was heavily affected by the tsunami of December 26, 2004. To examine its impact on seagrass macrofaunal communities, we compared the abundance, diversity and taxa composition by quantitative samplings in 2001 (before the tsunami) and in 2005 and 2006 (after the tsunami). Macrobenthic animals and sediments were collected from vegetated and nonvegetated areas of two sites that had received different levels of tsunami disturbances. A large decline in abundance and diversity was observed in the nonvegetated areas after the tsunami, whereas an increase was observed in the vegetated areas. The magnitude of decline and subsequent recovery of abundance and diversity of macrobenthic animals in nonvegetated areas were similar between the two sites, suggesting that their temporal changes were not solely related to the magnitude of the tsunami disturbance. Similarity of the benthic animals differed greatly between 2001 and 2005-2006 at the nonvegetated areas, whereas it varied less among the 3 years at the seagrass-vegetated areas. This study demonstrated that the presence of seagrass vegetation alters the patterns of temporal variation in macrofaunal assemblages and subsequent recovery processes following a tsunami. (C) 2010 Elsevier Ltd. All rights reserved.
  • Masahiro Tsujino, Masakazu Hori, Takehiro Okuda, Masahiro Nakaoka, Tomoko Yamamoto, Takashi Noda
    POPULATION ECOLOGY 52 1 171 - 180 2010年01月 [査読有り][通常論文]
     
    It is well known that the similarity in species composition between two communities decays with the geographic distance that separates them. It is thus likely that the similarity in the dynamics of two communities also decays with distance, because the distance-decay relationship is fundamental in nature. However, the distance-decay relationships of community dynamics have not yet been revealed. We used transition matrix models to evaluate distance-decay relationships of seasonal community dynamics (from spring to summer) in rocky intertidal sessile assemblages along the Pacific coast of Japan between 31A degrees N and 43A degrees N. We evaluated the distance-decay relationships of whole-community dynamics and of three dynamics-related components-recruitment, disturbance, and species interaction (competition and facilitation)-for communities separated by distances ranging from several meters to thousands of kilometers. The similarity of the recruitment dynamics among communities declined rapidly with distance within the fine spatial scale, but only moderately within larger scales. The similarity of the disturbance dynamics was independent of distance, and the similarity of species interaction declined slightly with increasing distance. The similarity of whole-community dynamics declined rapidly with distance at a fine spatial scale and moderately at larger scales. The fact that the distance-decay relationship of whole-community dynamics was similar to that of recruitment may suggest that recruitment processes are the most important determinant of spatial variability of community dynamics at our study sites during the study period.
  • Katsumasa Yamada, Masakazu Hori, Yoshiyuki Tanaka, Natsuki Hasegawa, Masahiro Nakaoka
    ESTUARINE COASTAL AND SHELF SCIENCE 86 1 71 - 82 2010年01月 [査読有り][通常論文]
     
    We examined the variation in habitat use and diet of three dominant fish species (Myoxocephalus brandti, Pholidapus dybowskii, and Pholis crassispina) in a seagrass meadow in the Akkeshi-ko estuary in northeastern Japan, where broad and dense Zostera marina beds exist, using a semi-quantitative census of the fishes and analyses of their stomach contents. Differences among the three fish species in the temporal variation in abundance of each age class (mainly 1- and 2-year age classes) indicated that the temporal pattern of utilization of the seagrass meadow were different among them. In the semi-quantitative dietary analysis, two prey categories, i.e., taxonomic group (order and suborder) and functional group, were used to explain the variation in prey composition with size-dependent changes. The six prey functional groups were classified based on the ecological traits of the prey, i.e., trophic level, size, and life type (habitat and behavior). Ontogenetic shifts in prey of the three fish species could be fully explained by a combination of the two prey categories, and not by the use of only one category (taxonomic or functional group). The pattern of ontogenetic shifts in prey differed among the fish species and size (age) classes. These results indicate that segregation of habitat (seagrass meadow) and prey group (taxonomic and functional group) is performed among the three species, which may contribute to their coexistence in this estuary. (C) 2009 Elsevier Ltd. All rights reserved.
  • Okuda T, Noda T, Yamamoto T, Hori M, Nakaoka M
    Japanese Journal of Ecology 60 2 227 - 239 2010年 [査読有り][通常論文]
  • Masakazu Hori, Takao Suzuki, Yaowaluk Monthum, Tippamas Srisombat, Yoshiyuki Tanaka, Masahiro Nakaoka, Hiroshi Mukai
    MARINE BIOLOGY 156 7 1447 - 1458 2009年06月 [査読有り][通常論文]
     
    Seagrass species function as typical foundation species that unifies most ecosystem processes. This ecosystem role depends largely on the morphological characteristics and structural complexity of seagrass beds, including their ecological importance for fish species. This study examined relationships between seagrass bed characteristics and associated fish communities in mixed seagrass beds. Correspondence analysis (CA) and canonical correlation analysis (CCoA) were performed to estimate relationships for individual seagrass bed characteristics. The CCoA results revealed that species richness and three-dimensional structure of seagrass had great effect on the biomass and richness of the associated fish community. The CA results revealed that the relative importance of seagrass bed characteristics differed among fish functional groups including fishes appearing on the surface of, inside, and on the bottom of seagrass beds. The fishes found on the surface of the beds preferred beds with low seagrass biomass and high three-dimensional structure, those inside the beds preferred beds with high seagrass biomass and high three-dimensional structure, and those on the bottom of the beds preferred locations with low seagrass biomass and low three-dimensional structure. The results of this study provide compelling evidence that seagrass beds with high species diversity and high three-dimensional structure, but intermediate biomass, may provide the great benefit to the associated fish community. Such niche complementarity among fishes may be a process facilitated by seagrass diversity for secondary production as an ecosystem functioning.
  • Takehiro Okuda, Takashi Noda, Tomoko Yamamoto, Masakazu Hori, Masahiro Nakaoka
    JOURNAL OF ANIMAL ECOLOGY 78 2 328 - 337 2009年03月 [査読有り][通常論文]
     
    Although latitudinal gradients in species richness within a region are observed in a range of taxa and habitats, little is known about variability in its scale dependence or causal processes. The scale-dependent variability of latitudinal gradients in species richness can be affected by latitudinal differences in (i) the regional relative abundance distribution, and (ii) the degree of aggregated distribution (i.e., intraspecific aggregation and interspecific segregation; henceforth, the degree of aggregation) reflecting differences in ecological processes among regions, which are not mutually exclusive. In rocky intertidal sessile animal assemblages along Japan's Pacific coast (between 31 degrees N and 43 degrees N), scale-dependent variability of the latitudinal gradient in species richness and its causal mechanisms were examined by explicitly incorporating three hierarchical spatial scales into the monitoring design: plots (50 x 100 cm), shores (78 to 235 m), and regions (16.7 to 42.5 km). To evaluate latitudinal differences in the degree of aggregation, the degree of intraspecific aggregation at each spatial scale in each region was examined using the standardized Morishita index. Furthermore, the observed species richness was compared with the species richness expected by random sampling from the regional species pool using randomization tests. Latitudinal gradients in species richness were observed at all spatial scales, but the gradients became steadily more moderate with decreasing spatial scale. The slope of the relative abundance distribution decreased with decreasing latitude. Tests of an index of intraspecific aggregation and randomization tests indicated that although species richness at smaller scales differed significantly from species richness expected based on a random distribution, the degree of aggregation did not vary with latitude. Although some ecological processes (possibly species sorting) may have played a role in determining species richness at small spatial scales, the importance of these processes did not vary with latitude. Thus, scale-dependent variability in the latitudinal gradient of species richness appears to be explained mainly by latitudinal differences in the regional relative abundance distribution by imposing statistical constraint caused by decreasing grain size.
  • Takehisa Yamakita, Masahiro Nakaoka
    POPULATION ECOLOGY 51 1 33 - 40 2009年01月 [査読有り][通常論文]
     
    Although the importance of spatial scale in ecology has been increasingly recognized, the effects on ecological processes of changing the grain size of the observation have rarely been tested for empirical populations. A seagrass bed is an ideal system to study scale-dependency because it occurs in two-dimensional shallow soft-bottoms and can be monitored on a broader scale by using remote-sensing techniques. To investigate the grain dependency of seagrass spatial dynamics, we analyzed the effect of neighboring vegetation on the annual transition between vegetated and unvegetated states in a seagrass meadow in Futtsu, Tokyo Bay. The presence or absence of seagrass vegetation was observed at different grains from aerial photographs taken annually over 17 years. We detected the presence of a neighboring effect both in the increasing process (transition from the unvegetated to the vegetated state) and the decreasing process (vice versa) of vegetation. In the increasing process, the intensity of the neighboring effect was positive with the small grain, but the effect decreased to 0 with grain of ca. 20 m. In the decreasing process, the neighboring effect was negative with the small grain and increased to 0 with grain of ca. 30 m. The observed grain dependency in the neighboring effects also varied among different positions of the bed and among different years. The grain dependency in the increasing process cannot solely be explained by shoot elongation of the seagrass, which can cause positive neighboring effects only at small grain (a parts per thousand currency sign6 m). The neighboring effect at the greater grain can be regarded as an emergent property.
  • Masahiro Nakaoka, Masatoshi Matsumasa, Tetsuhiko Toyohara, Susan L. Williams
    MARINE BIOLOGY 153 4 589 - 598 2008年02月 [査読有り][通常論文]
     
    Eelgrass, Zostera marina, produces two types of shoots: morphologically simple vegetative shoots and highly branched flowering (reproductive) shoots, the latter found only in summer months. We examined whether the abundance and diversity of mobile epifaunal assemblage are affected by the presence of flowering shoots in an eelgrass meadow of Otsuchi Bay, northeastern Japan. Comparisons of epifauna in natural vegetation revealed that density and species richness did not differ significantly between sites consisting of both flowering and vegetative shoots, and those only of vegetative shoots. A transplant experiment, conducted to examine the colonization rates of epifauna to defaunated eelgrass planted with different combination of vegetative and flowering shoots, showed no obvious variation in abundance and species richness. At species level, the density of some species such as a tanaid Zeuxo sp. and a polychaete Platynereis sp. was higher at sites and/or treatments with flowering shoots, whereas that of some gastropods, such as Lirularia iridescens and Siphonacmea oblongata was higher at sites without flowering shoots. The species-specific response led to dissimilarity of epifaunal assemblage between sites and among treatments with different densities of vegetative and flowering shoots. Similar patterns observed for natural vegetation and the transplant experiment suggest that the variation in assemblage structure is caused by habitat selection of each species, for example, the utilization of flowering shoots as feeding ground and nursery by Zeuxo sp.
  • Katsumasa Yamada, Masakazu Hori, Yoshiyuki Tanaka, Natsuki Hasegawa, Masahiro Nakaoka
    HYDROBIOLOGIA 592 1 345 - 358 2007年11月 [査読有り][通常論文]
     
    Temporal and spatial variation of the macrofaunal community was investigated in seagrass meadows in Akkeshi-ko estuary and coastal area of Akkeshi Bay, northern Japan. We specifically addressed the question of how the salinity gradient in seagrass meadows affects the species richness, abundance and similarity of faunal groups classified based on the degree of association with the seagrasses, i.e. highly motile species that drift in the water column among seagrass blades (drift-fauna, DF group) and less motile species that are tightly associated with seagrass substrates (seagrass-associated fauna, SA group). A total of 70 species were collected semi-quantitatively using an epibenthic sledge, among which more than one third of the species were captured in all areas, and a quarter of species only in the marine area. Significant spatial variation in species richness, as well as a positive relationship between salinity and species richness was found for most sampling occasions and for both functional groups. Whereas, relationship between salinity and abundance of macrofauna was not clear although significant time and site interactions were found for both functional groups. Patterns of similarity of assemblages varied between the functional groups: clear differences by sampling sites were discerned for DF group but not for SA group. These results provided evidence that the macrofaunal community structures in seagrass beds varied with the salinity gradient, but the pattern differed with time and between functional groups, possibly due to the effect of biotic and abiotic factors that also changed with salinity.
  • Hiroshi Kawai, Mitsunobu Kamiya, Teruhisa Komatsu, Masahiro Nakaoka, Tomoko Yamamoto, Marine Life, Research Group of, Takeno Marine Life Research, Group of Takeno
    ALGAE 22 1 37  The Korean Society of Phycology 2007年03月 [査読有り][通常論文]
  • Yoshida M, Kouchi N, Nakaoka M
    Japanese Journal of Conservation Ecology 12 1 10 - 19 日本生態学会 2007年 [査読有り][通常論文]
     
    市民参加型モニタリングにより海草藻場の空間動態を正確に把握するためには、リモートセンシング等で得られる空間分布情報との比較解析により、データの精度および代表性を評価することが必要である。そこで、2004年1月から2005年1月にかけて日本自然保護協会によって沖縄島北東部で行われた市民参加型モニタリング(ジャングサウォッチ)と同時に無人観測気球を使って低高度・高解像度で撮影された海草藻場の空中写真を解析し、両方法の有効性を検討した。ジャングサウォッチと空中写真の解析は、調査期間中に頻発した台風に伴う撹乱による海草藻場面積の減少を同様にとらえており、両方法が藻場全体スケールおよび局所スケールでの時間変動を追跡するモニタリング手法として有効であることが明らかになった。ジャングサウォッチでは、空中写真では判別不可能な海草の種ごとの被度変化、および種多様性の変動も明らかにすることができた。一方、空中写真は面積1m^2以上の植生部(パッチ)の判別が可能であり、パッチの面積頻度分布や、パッチの消失率、形成率、連続植生部からの分断化などの変動プロセスを解析できた。ジャングサウォッチによる海草被度と、空中写真から判読した藻場の植被率の関係について、写真からの読み取り面積を段階的に変化させて、両者の相関係数を比較したところ、一部を除き有意な正の相関が認められた。しかし、読み取り範囲の変化に伴う相関係数の変化のパターンは、年により異なっており、これには、両年における海草藻場の全体の植被率や連続性の違いが関連している可能性が示唆された。市民参加型モニタリングと低高度・高解像度で撮影した空中写真の解析を統合的に行うことで、両方法の制約を克服した海草藻場の空間動態の様式およびそのプロセスの解明が進むことが期待される。
  • Yoshiyuki Tanaka, Masahiro Nakaoka
    MARINE ECOLOGY PROGRESS SERIES 350 63 - 70 2007年 [査読有り][通常論文]
     
    Low light levels are a major factor determining the depth distribution of submerged macrophytes. In the Indo-Pacific tropical region, different seagrass species have specific zonation patterns from intertidal to subtidal areas along depth and light gradients. Cymodocea serrulata generally occurs in deeper water than Thalassia hemprichii and C. rotundata, suggesting that C. serrulata probably has the lowest minimum photon requirement of the 3 species. We compared photosynthesis and respiration balances of these 3 tropical seagrasses by examining photosynthesis-irradiance (P-E) curves for leaves and for the whole plant bodies, Sample collection and measurement were conducted on 2 occasions (July and February on Ishigaki Island, southwestern Japan. Leaf photosynthetic traits were not concordant with the observed zonation pattern of the species. When respiration rates of the root and rhizome were taken into account, T hemprichii had a significantly higher light compensation point (158.1 mu mol photons m(-2) S-1 in July, 187.2 in February) than C. rotundata (47.9 in July, 41.0 in February) and C. serrulata (85.1 in July, 40.0 in February). The large amount of belowground respiration in T hemprichii was a major cause of the variation in the compensation irradiance. This result is in concordance with the realized distribution pattern of T hemprichii, which is sparse under low light conditions caused by depth or heavy siltation. Conversely, C. serrulata had less belowground biomass and a smaller respiration demand, enabling the species to maintain a better photosynthetic/respiration balance under lower light. C. rotundata had a lower saturating irradiance, a lower compensation point and a lower respiration rate than the other species. Thus, C. rotundata has the potential to inhabit the deepest water, although its realized distribution range is shallower than that of C. serrulata, suggesting that other factors limit the depth range of C. rotundata.
  • Selected Papers of the NaGISA Wrold Congress 2006 2007年 [査読有り][通常論文]
  • Selected Papers of the NaGISA Wrold Congress 2006 2007年 [査読有り][通常論文]
  • Naoko Kouchi, Masahiro Nakaoka, Hiroshi Mukai
    MARINE ECOLOGY-AN EVOLUTIONARY PERSPECTIVE 27 2 145 - 153 2006年06月 [査読有り][通常論文]
     
    Seagrass is an ephemeral habitat for epifaunal sessile invertebrates attaching on seagrass leaves, and spatial and temporal dynamics of seagrasses strongly affect the distribution of epifauna. Zostera caulescens Miki, a seagrass species endemic to Japan, provides a complex habitat for epifauna with two types of shoots: vegetative, less than 1 m tall, and flowering, 5-7 m tall. We conducted monthly field observations and a manipulative field experiment to investigate the effects of the seagrass vertical structure and its temporal variation on the distribution and recruitment of the encrusting bryozoan Microporella trigonellata. The density of M. trigonellata on the leaves of flowering shoots, located at the seagrass canopy, varied temporally, reaching maximum in summer and minimum in winter. In contrast, M. trigonellata density on the leaves of vegetative shoots near the sea floor was consistently low throughout the study period. Early recruit bryozoans also showed this temporal and vertical variation in density; thus spatial and temporal variation in recruitment determined the distribution of the whole colonies. The field experiment revealed that the recruitment rate of M. trigonellata was significantly higher at the higher position of the water column (3 m above the sea floor) than at the lower position (0.5 m) in June. However, the recruitment rate was higher at the lower position in October when most of the flowering shoots started falling down. The temporal change in bryozoan habitat selection is considered to be adaptive to maintain their population on the seagrass leaves that show complex temporal dynamics.
  • Masahiro Nakaoka, Norihiko Ito, Tomoko Yamamoto, Takehiro Okuda, Takashi Noda
    ECOLOGICAL RESEARCH 21 3 425 - 435 2006年05月 [査読有り][通常論文]
     
    Factors and processes affecting community structures operate at various spatial and temporal scales. We analyzed how similarities of rocky intertidal assemblages vary at different spatial scales using a nested, hierarchical sampling design. Intertidal assemblages consisting of algae, sessile animals, and mobile animals were censused on five rock walls at each of five shores chosen within each of six regions along the Pacific coast of Japan, encompassing 1,800 km of coastlines. Based on this sampling design, similarities in assemblages were calculated using both qualitative (presence/absence) and quantitative (percent cover and density) data, and compared at three spatial levels: (1) rock level (the finest spatial scale, encompassing several to hundreds of meters), (2) shore level (the intermediate spatial scale, encompassing several to tens of kilometers), and (3) region level (the broadest spatial scale, encompassing hundreds to thousands of kilometers). Cluster analysis showed that assemblages were categorized into distinct regional groups except for the two southern regions, but they did not separate clearly from each shore. A nested analysis of similarities revealed significant variation in similarities among regions and among shores within each region, with the former showing greater variation. Similarity was negatively correlated with geographic distance at the regional level but not at the shore or the rock levels. At the regional level, similarity decreased more rapidly with distance for mobile animals than sessile organisms. The analyses highlighted the importance of broad-scale abiotic/biotic factors such as oceanic current conditions and biogeographic factors in determining observed patterns in similarity of rocky intertidal assemblages.
  • Yoshiyuki Tanaka, Masahiro Nakaoka
    BOTANICA MARINA 49 5-6 365 - 371 2006年 [査読有り][通常論文]
     
    Sediment loading and siltation affect seagrasses directly by burying shoots, and indirectly by attenuating light through resuspension. In the Indo-Pacific tropical region, Cymodocea serrulata is considered to be one of the species most tolerant to burial and light attenuation, because it is able to form its canopy in a higher position above the bottom, due to the presence of a long vertical rhizome. To test whether C. serrulata survives in shaded environments by forming a tall canopy (through elongation of the vertical rhizome), we compared variability of this species in vertical rhizome length among sites with different levels of siltation and sedimentation with morphological variability in C. rotundata, which is less tolerant to the stresses. Monitoring of environmental conditions, seagrass collection and morphological measurements of seagrasses were carried out in a meadow in Japan and three meadows in Thailand. C. serrulata and C. rotundata showed different types of among-site variation. To produce a tall canopy, C. serrulata elongated vertical rhizomes, whereas C. rotundata extended blades. Upward elongation of the vertical rhizome or blade was not observed in either species in sites with heavier siltation, suggesting upward elongation is not related to low light stress or sedimental burial. As a conspicuous morphological trait, roots on vertical rhizomes of C. serrulata were abundant at sites where sediment deposition and erosion occur frequently. Having abundant roots on vertical rhizomes is considered to be adaptive for stabilizing unsettled sediment.
  • M Nakaoka
    POPULATION ECOLOGY 47 3 167 - 177 2005年12月 [査読有り][通常論文]
     
    Seagrass beds are some of the most productive parts of coastal ecosystems, hosting a wide variety of associated fauna. This paper reviews recent studies of animal-plant interactions in seagrass beds, focusing particularly on studies conducted in Japan and Thailand. Although the positive effect of seagrass habitat structure on animals has been widely acknowledged, the magnitude of this effect varies greatly among studies. A comparative study on epifaunal communities and a manipulative experiment using an infaunal bivalve revealed that behavioral and life-history traits of component species and their interactions influence the observed variation. Some recent studies have challenged the previously accepted view that direct herbivory on seagrasses is rare, and has a minor effect on the seagrass community. A series of studies of dugong herbivory revealed that the marine mammal has great impacts not only on seagrass productivity but also on the infaunal community. Furthermore, it has been found that seed predators have a negative influence on seed production and the subsequent recruitment of seagrass. Recent studies have also demonstrated significant effects of fine-scale landscape patterns in seagrass vegetation on productivity, species interactions and community structure in seagrass beds. Future research integrating new concepts and theories in ecology, such as metapopulation and hierarchy theories, with new research tools, such as molecular-genetic analyses and remote-sensing techniques, may aid in developing a more comprehensive understanding of population and community dynamics in seagrass beds.
  • M Watanabe, M Nakaoka, H Mukai
    BOTANICA MARINA 48 4 266 - 273 2005年 [査読有り][通常論文]
     
    Seasonal variations in vegetative growth and production of two seagrass species, Zostera asiatica and Z. marina, were investigated in Akkeshi Bay, northern Japan. Z. asiatica, a threatened species in Japan, was dominant, occurring from the intertidal zone to the deepest edge of the seagrass bed (5 m deep), whereas Z. marina was restricted to the shallower edge of the bed (<2 m). Above ground biomass and above ground net production per shoot were greater for Z. asiatica than for Z. marina. In contrast, shoot density was 3- to 4-fold higher for Z. marina. Biomass and production were minimum in winter to early spring (January to March), and maximum in summer (June to July) for both species. Annual production per unit area of Z. asiatica was larger than that of Z. marina (2033 and 1354 g DW m(-2) y(-1), respectively). Our findings reveal contrasting growth patterns for the two species: Z. asiatica allocates more resources to enlarging shoot size, whereas Z. marina allocates more to increasing shoot density by clonal propagation of rhizomes. Seagrass beds consisting of Z. asiatica contributed importantly to coastal ecosystems in Akkeshi Bay area because of high productivity.
  • T Okuda, T Noda, T Yamamoto, N Ito, M Nakaoka
    POPULATION ECOLOGY 46 2 159 - 170 2004年08月 [査読有り][通常論文]
     
    This study examined the latitudinal gradient of species diversity of rocky intertidal sessile assemblages on the slopes of rocks along the Northwestern Pacific coast of Japan, located between 31degreesN and 43degreesN, by explicitly incorporating an hierarchical spatial scale into the monitoring design. The specific questions were to examine, (1) whether there is a latitudinal gradient of regional diversity, (2) how spatial components of the regional diversity (local diversity and turnover diversity) vary with latitude depending on spatial scale, and (3) whether the latitudinal gradient differs between different measures of species diversity, i.e. species richness and Simpson's diversity index. We measured coverage and the presence or absence of all sessile organisms in a total of 150 census plots established at five shores in each of six regions. The results showed that there were clear latitudinal gradients in regional species richness and in species turnover among shores. However, these patterns were not reflected in smaller-scale local species richness. For Simpson's diversity index, there was no evidence of latitudinal clines either in regional diversity or in spatial components. These results suggest that relative abundance of common species does not vary along latitude, while the number of rare species increases with decreasing latitude.
  • Y Tanaka, M Nakaoka
    MARINE ECOLOGY PROGRESS SERIES 284 117 - 131 2004年 [査読有り][通常論文]
     
    The effects of emergence stress and morphological constraints on the distribution and growth of 3 subtropical seagrass species, Cymodocea rotundata, C. Serrulata and Thalassia hemprichii, were examined in a series of transplantation experiments and a laboratory desiccation experiment. C. rotundata and T hemprichii occur in both the intertidal and subtidal zones off Ishigaki Island, southwest Japan, whereas C. serrulata is found only in the subtidal zone. Within the same species, intertidal shoots for both C. robundata and T hemprichii are significantly smaller than subtidal shoots. A subtidal-to-intertidal transplantation experiment was conducted on 3 occasions: July and September 2001 and January 2002. In July and September, when the intertidal sites were exposed to air for a shorter period, shoot densities of the transplanted 3 species did not decrease. In contrast, the shoot densities of all 3 transplanted species decreased significantly in February, when the exposure to air was longer. The survival of C. serrulata (2% of the initial density) was much lower than that of C. rotundata (48%) and T hemprichii (48%). In subtidal-to-intertidal transplants, the size of C. rotundata and T hemprichii leaves decreased, approaching that of intertidal shoots, indicating high morphological plasticity. In situ observations revealed that transplanted seagrasses with large leaves were exposed to air for longer than were intertidal controls. In the desiccation experiment, T. hemprichii leaves had higher water contents than those of C. rotundata and C. serrulata. The morphological traits of C. rotundata and T hemprichii and their ability to change shoot size appear to be related to the better survival of these species in the intertidal area as compared to C. Serrulata. This is consistent with the observed variation in the species distribution in the intertidal zone.
  • M Nakaoka, N Kouchi, K Aioi
    AQUATIC BOTANY 77 4 277 - 293 2003年12月 [査読有り][通常論文]
     
    Zostera caulescens occurs only in limited localities around Japan and Korea, and is listed as a threatened plant species in Japan. We present the first quantitative data on seasonal dynamics of Z. caulescens based on a 13-month field study of a subtidal seagrass bed (4-6 m deep) in Funakoshi Bay, northeastern Japan. We investigated the relative importance of flowering shoots on total net production: these flowering shoots form a canopy structure several meters above the sea bottom. Flowering shoots were observed throughout the year but showed large seasonal variation in density, with a maximum in spring to summer (>30 shoots m(-2)) and a minimum in winter (3 shoots m(-2)). The density of vegetative shoots fluctuated between 120 and 238 shoots m-2, but did not show a significant seasonal variation. Age distribution of both flowering and vegetative shoots showed marked seasonal variation, with the peak in recruitment observed during winter to early spring. Leaf plastochrone intervals were 2- to 3-fold shorter in summer than in winter, with an annual average of 15.3 and 18.1 days for flowering and vegetative shoots, respectively. On the basis of these data, the absolute age of the oldest flowering shoot was estimated at 13 months. Biomass and net production of Z. caulescens were highest in summer and lowest in winter. During spring to autumn, flowering shoots constituted more than 70% of both biomass and production, while the contribution of vegetative shoots dominated during winter, when the density of flowering shoots was low. Annual net production was estimated to be 292 and 134 g DW m(-2) per year for the aboveground parts of flowering and vegetative shoots, respectively, and 47 g DW m 2 per year for the belowground parts, giving a total of 473 g DW m(-2) per year. These findings demonstrated that the flowering shoots of Z caulescens are important not only for seed production, but also as major photosynthetic parts of the population, helping to achieve high primary production despite their distribution at the deeper parts of the multispecific seagrass bed. (C) 2003 Elsevier B.V All rights reserved.
  • N Tanaka, J Kuo, Y Omori, M Nakaoka, K Aioi
    JOURNAL OF PLANT RESEARCH 116 4 273 - 279 2003年08月 [査読有り][通常論文]
     
    Phylogenetic analysis of the plastid (chloroplast) DNA matK gene of Zosteraceae species was undertaken. A molecular phylogenetic tree based on matK sequence data showed the monophyly of Heterozostera tasmanica and subgenus Zosterella and did not support the separation of Heterozostera from the genus Zostera. The tree based on matK supported the monophyly of the subgenus Zostera, and showed that Zosteraceae consist of three main groups: Phyllospadix, which is clearly defined by being dioecious; the subgenus Zosterella and Heterozostera; and the subgenus Zostera. Character-state reconstruction of chromosome number and geographic distribution for our molecular phylogenetic tree showed that 2n = 12 is a plesiomorphic character for Zostera and Heterozostera, that the chromosome number was doubled or tripled in two lineages, and that the initial speciation of Zostera and Heterozostera occurred in the Northern Hemisphere. The matK tree showed the close affinity of Z. noltii and Z. japonica, which have disjunct distributions. Zostera marina, which is the only widely distributed species in the subgenus Zostera, also occurring in the northern Atlantic, was shown to be embedded within other subgenus Zostera species.
  • T Yamamoto, M Nakaoka, T Komatsu, H Kawai, K Ohwada
    MARINE POLLUTION BULLETIN 47 1-6 91 - 98 2003年 [査読有り][通常論文]
     
    The impact of a heavy-oil spill from the Nakhodka on an intertidal animal community, and the recovery process of animals from the damage were surveyed from the autumn of 1997 to the spring of 2001. The field study was carried out in the rocky coast of Imago-Ura Cove, located along the Sea of Japan, where clean-up operations for oil pollution had been conducted less intensely than in other polluted areas. We have examined individual number of each animal taxon by continuously placing a quadrat of 5 m width along the entire intertidal zone of the cove. A total of 76 invertebrate taxa including 57 species of mollusks, 10 species of crustaceans were observed during the survey. The number of taxa increased from 1998 to 1999 in areas where the initial oil pollution was intense. Total individual number of benthic animals continued to increase from 1998 to 2000 in the polluted areas. The impact of oil on benthic animals was different from species to species. Some species such as Cellana toreuma and Monodonta labio confusa increased rapidly after the oil spill, whereas other species such as Patelloida saccharina lanx and Septifer virgatus did not show any apparent temporal tendencies. Population size structure of P. saccharina lanx varied greatly among years, however that of M. labio confusa did not. For P. saccharina lanx, recruitment was unsuccessful in 1997, possibly due to the effect of oil pollution. These differences in responses to oil pollution among benthic animals are considered to be caused by the differences in habitat use, susceptibility to heavy-oil, life history and migration ability. The findings suggest that it took at least 2-3 years for the intertidal animal community to recover to its original level after the oil spill. (C) 2003 Elsevier Science Ltd. All rights reserved.
  • 保全生態学研究 2003年 [査読有り][通常論文]
  • 沿岸海洋研究 2003年 [査読有り][通常論文]
  • K Teruhisa, N Masahiro, K Hiroshi, Y Tomoko, O Kouichi
    MARINE POLLUTION BULLETIN 47 1-6 99 - 104 2003年 [査読有り][通常論文]
     
    A major heavy-oil spill from the Russian tanker Nakhodka occurred in the Sea of Japan on 2 January 1997. We investigated the impacts of this spill on a rocky intertidal ecosystem along the southern coast of the Sea of Japan. We selected Imago-Ura Cove as our study site to observe temporal changes along the oiled shore, because minimal cleaning effort was made in this area. Field surveys were conducted every autumn and spring from 1997 to 2000. We measured coverage by macroalgae in 1 x 1-m(2) quadrats and counted the animals in 5 x 5-m(2) quadrats along the intertidal zone. Changes in the ecosystem caused by the oil spill were analyzed by applying a geographical information system (GIS) to the Sea of Japan for the first time. The GIS showed that following the accident there were heavily oiled areas in sheltered regions, but these decreased over the three years. It also showed that coverage by macroalgae and the number of animals increased, although some species of algae with microscopic sporophyte generations, and some populations of perennial shellfish, remained stable or decreased during the study period. GIS was able to trace temporal changes in intertidal communities resulting from the impacts of heavy oil on flora and fauna at a spatial scale of 10-100 m. GIS is thus a practical tool for visualizing, analyzing, and monitoring changes in an ecosystem polluted by oil, taking into account topographic differences along the coastline. (C) 2003 Elsevier Science Ltd. All rights reserved.
  • M Nakaoka, H Mukai, S Chunhabundit
    ECOLOGICAL RESEARCH 17 6 625 - 638 2002年11月 [査読有り][通常論文]
     
    We studied the community structure and abundance of benthic animals in intertidal seagrass beds in Thailand, where dugongs (Dugong dugon ) feed on the seagrass Halophila ovalis . Our objective was to examine whether the benthic community was affected by the foraging activity of the dugongs, which can cause disturbance to the sediment. We collected a total of 4156 benthic animals from three study sites and classified them into 77 different taxa. A lucinid bivalve, Pillucina sp., was the most abundant taxa (approximately 80% of individuals). Taxa richness of the benthic animals was higher in intact H. ovalis vegetation compared to dugong trails at all sites. In general, the densities of five functional groups (classified by position on/in the sediment and motility) and five dominant taxa were higher in intact seagrass vegetation compared to dugong trails, although the magnitude of this difference varied among functional groups and taxa. Densities were at least threefold higher in the seagrass vegetation than in the dugong trails for epifauna and shallow infauna, but were at most twofold higher for deep infauna. Taxa richness and abundance of the benthic animals in the dugong trails were similar between the day following, and 7-9 days after, the creation of the trails. Thus, delayed and/or indirect effects of dugong herbivory on benthic communities were not detected in this study. These findings demonstrate that the foraging activity of dugongs in seagrass can have considerable impacts on the abundance and diversity of benthic organisms, although this effect varies among benthic animals with different lifestyles.
  • M Nakaoka
    AQUATIC BOTANY 72 2 99 - 106 2002年03月 [査読有り][通常論文]
     
    This paper reports the first evidence of seed predation by a tanaid crustacean on seagrasses Zostera marina and Z caulescens in Otsuchi Bay, northeastern Japan. A tanaid, Zeuxo sp., was found to live in spathes of the seagrasses. Spathes with the tanaid were observed to have bored seeds. Laboratory observations revealed that the tanaid consumes seeds by drilling a hole. For both seagrass species, tanaids and bored ovules were not observed for spathes before anthesis, whereas spathes with bored seeds and density of the tanaid increased after anthesis, from June to August. In August, 14 and 27% of seeds were found bored in Z marina and Z caulescens, respectively, suggesting that seed predation by the tanaid has considerable negative impact on seed production of the seagrasses. Some adult individuals of Zeuxo sp. in spathes had brood pouches containing eggs and juveniles. A large number of juveniles were found in spathes in August. Thus, the tanaid utilizes seagrass spathes not only as feeding site, but also as place of reproduction and a nursery. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Otsuchi Marine Science 2002年03月 [査読有り][通常論文]
  • Teruhisa Komatsu, Chiaki Igararashi, Ken-ichi Tatsukawa, Masahiro Nakaoka, Tomonori Hiraishi, Asahiko Taira
    FISHERIES SCIENCE 68 sup1 580 - 583 2002年 [査読有り][通常論文]
     
    Mapping of seagrass and seaweed beds is very important for management and conservation of sound littoral ecosystems and sustainable fisheries in the coastal waters. The methods to map spatial distribution of seagrass and seaweed beds are reviewed. They are classified into two categories. One is a direct method by visual observation and the other is an indirect method using a remote sensing apparatus. Indirect methods are divided into optical or hydro-acoustic methods. Indirect methods require sea truth by direct methods. Optical methods are image analysis of aerial photography or satellite imagery. They are effective for mapping broad areas but limited to shallow waters due to light attenuation in waters. Hydro-acoustic methods such as an echosounder and a side scan sonar have no limitation of turbidity The echosounder is practical to map vertically density and height distributions of seagrass and seaweed beds. The side scan sonar is appropriate for mapping broad horizontal distributions. Coupling of several indirect mapping methods is more useful than using only one method.
  • M Nakaoka, T Toyohara, M Matsumasa
    MARINE ECOLOGY-PUBBLICAZIONI DELLA STAZIONE ZOOLOGICA DI NAPOLI I 22 4 379 - 395 2001年12月 [査読有り][通常論文]
     
    A seagrass bed in Otsuchi Bay, northeastern Japan, consists of three seagrass species (Zostera marina, Z. caulescens and Z. caespitosa) that differ in morphology and phenology. We studied the mobile epifaunal community in the seagrass. bed to examine (1) whether seasonal and between-substrate variation in the epifaunal community agrees with variation in seagrass abundance and morphological complexity, and (2) whether patterns of seasonal and between-substrate variation vary among epifaunal species. We collected mobile epifauna from each of Z marina and Z caulescens on 11 occasions between October 1995 and November 1996 (at 1-1.5 month intervals) using a hand-closing net. A total of 9842 individuals of mobile epiphytic animals were collected and they were classified into 80 taxa. Abundance and species richness of the epifaunal community were high in summer to autumn and low in winter to spring, and diversity index and evenness were higher in Z marina than Z caulescens. However, patterns of seasonal and between-substrate variation in these parameters did not parallel those in seagrass abundance and complexity. Most of the dominant epifaunal species showed significant seasonal and between-substrate variation in abundance, although their patterns varied greatly among individual species. A cluster analysis recognized several distinct groups of animals showing similar seasonal and between-substrate variation. Our findings suggest that the observed variation in the epifaunal community is not determined by a single or some strong external factors but by complex interactions of multiple factors operating differently for each component species.
  • Otsuchi Marine Science 2001年03月 [査読有り][通常論文]
  • Nakaoka Masahiro, Iisumi Hitoshi
    Ecological research 15 4 415 - 424 Ecological Society of Japan 2000年12月 [査読有り]
  • M Nakaoka
    ECOLOGY 81 4 1031 - 1045 2000年04月 [査読有り][通常論文]
     
    Predators affect dynamics of prey populations not only by decreasing their survivorship, but also by changing other vital rates such as growth and reproduction. However, such nonlethal effects have rarely been examined experimentally in the field. In North Carolina estuaries, the hard clam Mercenaria mercenaria generally shows lower growth rates in habitats where predation rates are higher. Predator avoidance behavior of the clams (feeding inhibition) might be one of the factors responsible for this correlation. To examine possible effects of predators on clam growth, I first compared variation in clam growth rate among habitats with different predation pressure, and between predator-exclusion cages and uncaged controls. I then carried out a predator-enclosure experiment using the clam and the whelk Busycon cal-ica, a major predator on adult clams. Among-habitat variation in survivorship, predation rate, and growth rate was generally small or not detected in winter, while large variation was found for adult clams in spring, their major growing season. Growth rate of adults was highest in a mud bottom where survivorship was highest (>60%) due to low predation rates, and it was lowest in an oyster shell bottom where survivorship was lowest (<10%). For juveniles, on the other hand, growth rate did not differ significantly among habitats, nor did survivorship. Clams in the predator-exclusion cages showed nearly twice the growth rate of uncaged controls in spring but not in winter. Clam growth rates were thus lower in habitats with lower survivorship and higher predation rates, suggesting that the predators can affect growth rates. In the whelk-enclosure experiment, the clams were enclosed in cages with three different treatments: (1) with whelks capable of attacking clams, (2) with whelks isolated from the prey, and (3) without whelks (control). The shell and somatic growth rates of the clam were at least twice as high in the control than in the two experimental treatments. However, the growth rates did not differ significantly between the two experimental treatments. The clam growth rates were therefore reduced in the presence of whelks even with no direct contact between whelks and clams, suggesting that the decrease in growth rates is due to a behavioral response of the prey to indirect cues, such as water-borne chemical signals produced by whelks. These findings show that predatory whelks can affect clam population dynamics not only by decreasing survivorship directly, but also by decreasing future reproduction and survivorship indirectly by suppressing growth rates, and that the predator-avoidance behavior observed in previous studies has significant demographic consequences. The non lethal effects of predation on clam growth rate may also be responsible for observed variation in growth rates among habitats.
  • Masahiro Nakaoka, Tetsuhiko Toyohara
    BENTHOS RESEARCH 55 2 53  The Japanese Association of Benthology 2000年 [査読有り][通常論文]
  • Biologia Marina Mediterranea 2000年 [査読有り][通常論文]
  • Biologia Marina Mediterranea 2000年 [査読有り][通常論文]
  • Biologia Marina Mediterranea 2000年 [査読有り][通常論文]
  • Otsuchi Marine Science 2000年 [査読有り][通常論文]
  • T Toyohara, M Nakaoka, K Aioi
    MARINE ECOLOGY-PUBBLICAZIONI DELLA STAZIONE ZOOLOGICA DI NAPOLI I 20 3-4 273 - 289 1999年12月 [査読有り][通常論文]
     
    We studied the population dynamics and reproductive traits of two phytal gastropods, Lirularia iridescens and Hiloa tristis, inhabiting a seagrass bed consisting of two seagrass species, Zostera marina and Zostera caulescens, in Otsuchi Bay, north-eastern Japan. The main objectives of the study were to (1) determine seasonal and between-substrata variations in gastropod populations and (2) examine two major factors potentially responsible for the variations, namely space (seagrass) and food (epiphytes). The biomass of Z. mar ina reached a peak in summer and decreased through autumn, whereas the biomass of Z. caulescens showed little seasonal fluctuation. Epiphyte biomass was maximum in April and remained low from summer to winter on both seagrass substrata. The population densities of both gastropod species increased rapidly due to increases in their new recruits from May to July for L. iridescens, from June to October for H. tristis. Eggs of L. iridescens were found in almost all months of the study period, with a breeding peak in April, whereas oviposition of H. tristis occurred only from June to October. The new recruits of both gastropods grew rapidly, with their abundance decreasing from summer to autumn. The peak densities of new recruits of the two species coincide with that of seagrass biomass rather tl lan epiphyte biomass, and the juveniles grew when the epiphyte biomass was fairly low. Hence, large postrecruitment declines in gastropods may be caused by food shortage. Egg density, size structure and growth rate of both gastropod species were not significantly different between seagrass substrata. Total abundance was not significantly different for L. iridescens, For H. tristis, however, abundance was lower on Z. caulescens than Z. marina during most of the year, mainly due to higher post-recruitment decline on the former. The ability of L. iridescens to breed continuously may enable them to successfully inhabit two seagrass species with different phenology, whereas the much shorter breeding season of H. tristis, which coincides with the periods of higher Z. marina biomass, may be more adaptive for inhabiting Z. marina than Z. caulescens.
  • M Nakaoka, K Aioi
    MARINE ECOLOGY PROGRESS SERIES 184 97 - 103 1999年 [査読有り][通常論文]
     
    We studied small-scale variation in morphology and growth rate of the seagrass Halophila ovalis in an intertidal flat of Thailand coast where the seagrass bed is subjected to grazing by dugongs. Our objectives were to examine whether morphology and growth rate differ between rhizomes in different positions within a patch (center, edge and dugong trails), and to test whether H. ovalis shows plastic growth response to disturbance by dugong feeding. Seagrass biomass and leaf density were 3 to 4 times greater at the patch center than the patch edge and the dugong trails. In contrast, branching rate and internode length of rhizomes were significantly greater at the patch edge and dugong trails than at the patch center. The results of marking experiments of H, ovalis revealed that net production, leaf production and rhizome elongation rates were 2 to 3 times greater at the patch edge than at the center. Growth and production rates at the edge of the dugong trails and artificial trails mimicking dugong trails were not significantly higher than at the patch center. Nevertheless, significant differences in some morphological parameters such as branching frequency and internode length between the dugong trails and the patch center suggest that morphological changes in H. ovalis can be induced over short time scales. Recovery of H, ovalis after disturbance by dugong herbivory was estimated to be quite rapid (<20 d). High growth rates of H. ovalis were probably responsible for its persistence under grazing by dugongs.
  • M Nakaoka, S Ohta
    MARINE BIOLOGY 132 3 471 - 481 1998年10月 [査読有り][通常論文]
     
    Seasonal Variation in reproduction and population size structure was investigated for the suspension-feeding bivalve Limopsis tajimae Sowerby inhabiting the upper bathyal zone (300 m deep) of Suruga Bay, central Japan. The bivalve was collected at 1- to 4-month intervals for a period of 22 months, and bottom environment was monitored concurrently to detect factors affecting seasonality in the bivalve. Bottom water temperature, organic carbon and nitrogen contents in the sediments did not exhibit seasonal variation. Size-adjusted soft-tissue weight varied slightly, but statistically significantly between stations and months. However, its seasonal pattern was not obvious, and the pattern of temporal variation was totally different between stations. The sex ratio did not deviate from 1:1, and there was no significant difference between shell lengths of females and males. Females possess both immature small oocytes and large developed oocytes in their ovaries throughout the year, suggesting that they can potentially undergo year-round continuous reproduction. The proportion of developed oocytes in each female varied greatly from month to month, although no seasonal cycle was obvious. Population size structure of L. tajimae was polymodal. A mode of the smallest size class occurred in most months, suggesting long periods of bivalve recruitment. These findings indicate that seasonal variation in reproduction of the bivalve was negligible, probably reflecting constant physical and nutritive conditions of the bottom environment.
  • Masahiro Nakaoka
    Evolutionary Ecology 12 3 347 - 361 1998年 [査読有り][通常論文]
     
    The effects of the morphological constraint of maximum reproductive output (reproductive capacity) and the size at which individuals can avoid heavy mortality (refuge size) on the resource allocation pattern between growth and reproduction are investigated using a dynamic modelling approach for a population of Yoldia notabilis (Mollusca: Bivalvia) in Otsuchi Bay, northeastern Japan. A state variable model is developed using field data on shell length, somatic weight, production, survivorship and reproductive capacity of the bivalve. The optimal allocation pattern is characterized by sudden switching from growth to reproduction without the assumption of reproductive capacity, while simultaneous investment in growth and reproduction becomes optimal when maximum reproductive output is limited by reproductive capacity. Size-specific reproductive effort, size at maturity and the growth curve predicted by the latter model fit more closely to the field data, suggesting that size-limited reproductive capacity can play an important role in the evolution of the observed resource allocation pattern. The mortality pattern affects optimal size at maturity, but not size-specific reproductive effort after maturity. When refuge size is fixed, optimal size at maturity increases with survivorship above refuge size. Optimal size at maturity changes in a more complex way with changes in refuge size. Size at maturity remains constant when refuge size is small, increases when it is intermediate, and decreases when it is large. The results suggest that refuge size is an important factor in the evolution of size at maturity, although its contribution varies depending on the values of other factors, such as size-dependent production and survivorship above refuge size.
  • M Nakaoka
    OIKOS 79 1 59 - 68 1997年05月 [査読有り][通常論文]
     
    A population of the marine bivalve Yoldia notabilis in Otsuchi Bay, northeastern Japan shows large interannual fluctuations in recruitment rate and individual growth rate. The effects of these fluctuations on population growth rate were examined using a stochastic size-classified matrix model. Stochastic population growth rate (1n lambda(S)) estimated by numerical iterations differed greatly between models with lognormal distributions and normal distributions fitted to the fluctuating recruitment rate. The estimates of 1n lambda S, its confidence interval and 1n mu (growth rate of average population size) increased greatly with an arbitrary increase in the variance of recruitment rate, while the variance in individual growth rate has less effects on the estimates of these parameters. The fluctuation in recruitment has therefore more impact on the population dynamics. The stochastic growth rate 1n lambda(S) was always no greater than 1n mu, the latter equivalent to the deterministic growth rate, and their difference increased with the variance in the recruitment rate and the individual growth rate, suggesting that the population growth rate estimate based on average vital rates may be an overestimate. These findings demonstrate that the estimates of population growth rates are greatly influenced by the types of probability distributions fitted to fluctuating vital rates, and by the types of vital rates which are subjected to fluctuation.
  • M Nakaoka
    RESEARCHES ON POPULATION ECOLOGY 38 2 141 - 152 1996年12月 [査読有り][通常論文]
     
    Recent developments of the theory of stochastic matrix modeling have made it possible to estimate general properties of age- and size-structured populations in fluctuating environments. However, applications of the theory to natural populations are still few. The empirical studies which have used stochastic matrix models are reviewed here to examine whether predictions made by the theory can be generally found in wild populations. The organisms studied include terrestrial grasses and herbs, a seaweed, a fish, a reptile, a deer and some marine invertebrates. In all the studies, the stochastic population growth rate (In lambda(s)) was no greater than the deterministic population growth rate determined using average vital rates, suggesting that the model based only on average vital rates may overestimate growth rates of populations in fluctuating environments. Factors affecting In lambda(s) include the magnitude of variation in vital rates, probability distribution of random environments, fluctuation in different types of vital rates, covariances between vital rates, and autocorrelation between successive environments. However, comprehensive rules were hardly found through the comparisons of the empirical studies. Based on shortcomings of previous studies, I address some important subjects which should be examined in future studies.
  • M Nakaoka
    JOURNAL OF SHELLFISH RESEARCH 15 2 355 - 362 1996年06月 [査読有り][通常論文]
     
    Age-specific survivorship of the bivalve Yoldia notabilis was estimated by quantitative field samplings, and the possible effect of predation by the crab Paradorippe granulata on its survivorship pattern was examined by laboratory experiments. The annual mortality rate in the field was high (>86%) in the two youngest year classes, whereas mortality was lower (<40%) in the classes older than 3 y, leading to Deevey's type 3 survivorship curve. Field mortality was size dependent; bivalves smaller than 10 mm in shell length suffered high mortality (>68%), whereas those larger than 10 mm did not (<40%), regardless of actual age. Burrowing depth of Y. notabilis increased with shell length, although considerable variation was found among larger individuals. The laboratory experiment revealed that crabs preferred smaller bivalves. The resultant size-related mortality pattern in the experiment was similar to that in the field, suggesting that size-selective predation by P. granulata contributes to the size-specific survivorship pattern of Y. notabilis. Size-selective predation by this crab did not depend on the size-dependent burrowing ability of the bivalve, because small sizes were preferred even when bivalves of all sizes were constrained to live in shallow sediments.
  • M NAKAOKA
    MARINE ECOLOGY PROGRESS SERIES 114 1-2 129 - 137 1994年11月 [査読有り][通常論文]
     
    Between-site variation in age and size at maturity, egg size, fecundity and reproductive effort was measured in a population of the bivalve Yoldia notabilis in Otsuchi Bay, northeastern japan, and tests were conducted to address whether these reproductive traits are dependent on size or age. The diameter of mature oocytes increased with age and size, as did fecundity and reproductive effort. Most individuals were mature at 3 yr of age (Age 3) at the shallower station (10 m depth) and at Age 4 at the deeper station (14 m), although the size at maturity was similar (between 15 and 20 mm shell length) at the. 2 stations. This is the size at which the bivalve escapes heavy predation from the crab Paradorippe granulata. Age-specific reproductive effort was higher at the shallower station than at the deeper one; however, reproductive effort did not differ significantly between stations when compared on the basis of size, These lines of evidence suggest that the onset of reproduction and the schedule of reproductive effort depend more on size than age. The observed size-dependency of reproduction is considered to be associated with size-dependent mortality rate due to predation, as well as with size-limited reproductive capacity due. to morphological constraints in shell volume.
  • M NAKAOKA, S MATSUI
    MARINE BIOLOGY 119 3 397 - 404 1994年06月 [査読有り][通常論文]
     
    Annual variation in the growth rate of the protobranch bivalve Yoldia notnbilis (collected in Otsuchi Bay, northeastern Japan between 1989 and 1991) was determined by measuring shell length at successive growth lines. Factors affecting growth rates were assessed by examining long-term environmental data. Shell cross-sections of Y. notabilis showed a clear pattern of internal growth lines which formed simultaneously with the annual external lines on the outer shell surface. Hence, they were used as an age marker. A maximum lifespan of 17 yr was determined for this species, and a sigmoidal growth curve was obtained by the internal growth line analysis. Examination ofthe growth lines also revealed a large annual variation in growth rate, fluctuating as much as 32-fold during the past 9 yr. The variation correlated negatively with water temperature and positively with chlorophyll a content in the water column. It is suggested that the variation in annual growth rate is dependent on food supply during the spring phytoplankton bloom which varies from year to year according to the flow of the cold Oyashio current each spring.
  • M NAKAOKA
    RESEARCHES ON POPULATION ECOLOGY 35 2 199 - 213 1993年12月 [査読有り][通常論文]
     
    Long-term variation in recruitment was estimated by constructing projection matrices for a marine bivalve, Yoldia notabilis, at two stations in Otsuchi Bay, northeastern Japan, and the effeCtS of its variation on population dynamics were examined using a simple matrix model. The matrix model was developed from the Leslie matrix, in which the population growth rate lambda was expressed as a function of recruitment rate r0. The equilibrium recruitment rate r(s), or the recruitment rate required to maintain population at constant size (lambda=1), was expressed by the reciprocal of the reproductive value of a newly recruited individual. The estimates of r(s) for the field population were lower at the shallower station than at the deeper station, reflecting higher survivorship and fecundity. Past recruitment rate estimated both by the field samplings for 3 years and by the back-calculation from the current age structure for over 10 years showed large yearly variation, ranging between 0 and 58.6 x 10(-4). The estimates were larger than r(s), and hence, large enough to increase population size (lambda > 1) only in approximately one-third of the estimated years. This suggests that the population has been maintained by occasional successful recruitment occurring once every few years.
  • M NAKAOKA
    MARINE ECOLOGY PROGRESS SERIES 88 2-3 215 - 223 1992年11月 [査読有り][通常論文]
     
    A 1 yr field study of a long-lived protobranch bivalve, Yoldia notabilis Yokoyama, in Otsuchi Bay, northeastern Japan, revealed that there was a large seasonal and spatial variation in growth rate and secondary production, and that primary production in the water column and following organic supply to the bottom were responsible for the variation. Both shell and soft tissue growth of each of 9 year-classes were rapid in spring, and slow or even negative in other seasons. The rapid growth coincided well with the occurrence of spring phytoplankton bloom in the water column and the peak of organic flux to the bottom. Mean shell length and mean soft tissue weight of each year-class were larger, and the growth rates of shell and soft tissue as well as the secondary production were higher at the shallower station (10 m deep) than at the deeper station (14 m). The differences in size, growth rate and production between the 2 stations were consistent with the local difference in food supply from the water column to the bottom, but not related to other environmental factors such as temperature, salinity, organic content in the sediment and density of Y. notabilis. Annual production was 1.38 and 0.89 g ash-free dry wt 0.1 m-2 yr-1, giving P/B ratios of 0.76 and 0.41 for the shallow and deep station respectively. Food intake by Y. notabilis between February and April 1991 was estimated to be 26.4 and 13.9 g C m-2 (shallow and deep respectively), which amounted to ca 10 % of the primary production and 30 to 40 % of the organic supply to the bottom. These estimates suggested that the Y. notabilis population plays an important role in the energy flow from pelagic to benthic communities.
  • MASAHIRO NAKAOKA
    BENTHOS RESEARCH 1992 43 53  The Japanese Association of Benthology 1992年 [査読有り][通常論文]

書籍

  • 堀, 正和, 桑江, 朝比呂 
    地人書館 2017年06月 (ISBN: 9784805209097) xii, 254p, 図版 [4] p
  • 日本生態学会, 津田, 敦, 森田, 健太郎, 仲岡, 雅裕, 齊藤, 宏明, 河村, 知彦, 鈴木, 光次, 山村, 織生, 高橋, 一生 
    共立出版 2016年02月 (ISBN: 9784320057456) xi, 305p, 図版 [4] p
  • 水産学シリーズ 169 浅海域の生態系サービス. 海の恵みと持続的利用
    小路淳, 堀正和, 山下洋 (範囲:地球環境変動と生態系サービス、人間活動の関連性の解明に向けて)
    恒星社厚生閣 2011年 129-143
  • エコロジー講座4 地球環境問題に挑む生態学
    日本生態学会, 仲岡雅裕 
    文一総合出版 2011年
  • エコロジー講座3 なぜ地球の生きものを守るのか
    日本生態学会 (範囲:アマモ場の生物多様性と機能)
    文一総合出版 2010年 6-17
  • シリーズ群集生態学4 生態系と群集をむすぶ
    大串隆之, 近藤倫生, 仲岡雅裕 (範囲:気候変動にともなう沿岸生態系の変化?生物群集から考える)
    京都大学学術出版会 2008年 179-204
  • ジャングサウォッチハンドブック
    仲岡雅裕, 河内直子, 吉田正人, 大野正人, 小林愛 
    日本自然保護協会 2006年 36
  • 流出油の海洋生態系への影響 −ナホトカ号の事例を中心に−
    大和田紘一, 小山次朗, 広石伸互 (範囲:GISを用いた岩礁域潮間帯生物相に及ぼすナホトカ号重油流出事故の影響評価. 流出油の海洋生態系への影響)
    恒星社厚生閣 2005年 120-134
  • 三陸の海と生物―フィールドサイエンスの新しい展開
    宮崎信之 (範囲:海草藻場の生物多様性)
    サイエンティスト社 2005年 66-83
  • 海洋ベントスの生態学
    日本ベントス学会 (範囲:個体群と生活史)
    東海大学出版会 2003年 33-115

その他活動・業績

受賞

  • 2003年 個体群生態学会 個体群生態学会奨励賞
     Population and community ecology of marine benthic organisms: From single-species study to multi-disciplinary and multi-scale approaches for understanding processes and dynamics of open populations and communities

共同研究・競争的資金等の研究課題

  • 東南アジア沿岸域の生物多様性評価:ベースライン復元による現況・将来予測の高精度化
    日本学術振興会:科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B))
    研究期間 : 2020年10月 -2026年03月 
    代表者 : 仲岡 雅裕, 百田 恭輔, 諏訪 錬平, 山北 剛久
  • コーラル・トライアングルにおけるブルーカーボン生態系とその多面的サービスの包括的評価と保全戦略
    JST-JICA:地球規模課題対応国際科学技術協力事業
    研究期間 : 2017年04月 -2022年03月 
    代表者 : 灘岡和夫
  • 海洋「脱」酸性化:アマモ場の酸性化緩和機能の検証と生物群集・生態系機能変動予測
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2016年04月 -2021年03月 
    代表者 : 仲岡 雅裕, 栗原 晴子, 藤井 賢彦
     
    アマモ場は光合成により二酸化炭素を吸収するため、海洋酸性化を緩和する機能がある。本研究では、アマモ場の海洋酸性化緩和機能の大きさと空間的な影響範囲を明らかにすると共に、その効果の海洋生物群集への影響を評価する。この目的を達成するため、(A) 北海道東部の環境条件の異なる複数のアマモ場でpH, CO2濃度の連続観測を実施し、(B) 生態系モデルにより緩和機能の影響範囲を評価する。また、(C) 現場のpH・CO2濃度の変動を再現したメソコズム実験により、緩和機能が生物群集に与える影響を検証し、(D)以上の結果を取り入れた統合解析により、アマモ場生物群集の動態に関する将来予測を行う。 2年目にあたる平成29年度は、前年台風により異常値が出た夏季を中心に厚岸湖および厚岸湾のpH, CO2濃度の連続観測を継続した。これらの観測から、アマモ場のpH, CO2濃度の変動パターンが年により大きく異なることが判明した。この原因を明らかにするために、昨年度に開発した流動・生態系構造を考慮した炭素循環予測モデルによる動態予測を行ったところ、淡水流入に伴うアマモの生物量の変化がpH, CO2濃度の変動に大きく関与している可能性が示唆された。 メソコズム実験においては、昨年度に引き続き、水温と二酸化炭素濃度を同時に操作する室内実験によりアマモ、付着藻類、植食性巻貝の相互作用の検証を進めた。その結果、水温上昇の効果に比べ、二酸化炭素分圧の変化が相互作用の変化に与える効果は不明瞭であった。また、上記で観測したpH, CO2濃度の時間変化も考慮した操作実験系の開発を開始した。
  • 海洋プラスチックごみに係る動態・環境影響の体系的解明と計測手法の高度化に係る研究
    環境省:環境研究総合推進費
    研究期間 : 2018年04月 -2021年03月 
    代表者 : 磯辺篤彦
  • 社会・生態システムの統合化による自然資本・生態系サービスの予測評価
    環境省:環境研究総合推進費
    研究期間 : 2016年04月 -2021年03月 
    代表者 : 武内和彦
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 仲岡 雅裕, 水川 薫子, 頼末 武史
     
    本研究では、海洋中に増加しているマイクロプラスチックが底生無脊椎動物に与える影響を評価することを目的とした。まず、調査地である北海道厚岸湾の堆積物中のマイクロプラスチック量は他地域と比較すると低い値であったが、漁業活動由来のファイバー状のものが多いことが判明した。次に、ムラサキイガイを対象とした室内実験により、水温上昇によりマイクロプラスチックの負の効果が増幅されることが判明した。さらに、野外に存在するPOPs(残留性有機汚染物質)をマイクロプラスチックに吸着させて、ムラサキイガイを対象に暴露実験を行ったところ、マイクロプラスチックを通じたPOPsの蓄積が生ずることが示唆された。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2012年04月 -2016年03月 
    代表者 : 笹 賀一郎, 福澤 加里部, 佐藤 冬樹, 東 隆行, 星野 洋一郎, 四ッ倉 典滋, 傳法 隆, 長坂 晶子, 仲岡 雅裕, 柴田 英昭, 秦 寛
     
    非カンラン岩地帯との比較から、カンラン岩地帯の流域と植生が、陸域における物質移動と沿岸域の水質環境や植物生産に与える影響を明らかにしようとした。 カンラン岩流域においては、水分の地表流出率が高く、DOC(溶存炭素)の流出量も多くなっている。DOCと土壌中のFeイオンとの有機―無機複合体の形成は、針葉樹林下において、秋期を中心に行われ、O層の下部より溶出する。また、SS(浮遊砂)の流出量は少なく、落葉の流出率が高くなっている。カンラン岩地帯の河川は沿岸域の水質環境や昆布の成育などに好条件をもたらしているが、水質環境の悪化などにより、コンブの藻場が縮小傾向にある状況も把握された。
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2012年04月 -2016年03月 
    代表者 : 堀 正和, 小路 淳, 仲岡 雅裕, 長谷川 夏樹
     
    環太平洋のアマモ場の生態系機能と生態系サービスの地域変異性を生み出す要因を解明することを目的に、日本産マガキの養殖のために日本から多くの種が移入している北米西海岸のアマモ場を対象に調査・解析を行った。その結果、移入種よりもマガキ養殖そのものがアマモの生態系機能と生態系サービスの変化を生じさせている傾向が確認された。マガキは本来の生息地である日本周辺海域ではアマモ場に隣接してカキ礁を形成することが多く、アマモ場と物質循環面で相互作用していたことが知られている。本結果は、マガキが移入先の北米西海岸でもアマモ場との相互作用を形成している可能性を示唆している。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2011年 -2012年 
    代表者 : 仲岡 雅裕, 福澤 加里部, 中路 達郎
     
    光学的な生態系測定法をアマモ場に適用することにより、海草類の地下部の生産量・分解量を評価する方法を確立することを目的とする。屋内水槽実験により、細根の生物量は炭素シンクとしての寄与は無視できないことが判明した。また、可視~近赤外波長の分光画像撮影により、加齢は細根における可視波長反射率を低下させ、枯死は反射率を全体的に低下させることが明らかになった。分光反射率から根の齢、炭素、窒素量が12~37%の誤差推定可能であった。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2009年 -2012年 
    代表者 : 仲岡 雅裕, 田中 法生, 堀 正和, 四ッ倉 典滋, 宮下 和士, 磯田 豊, 野田 隆史, 灘岡 和夫, 山本 智子, 浜口 昌巳
     
    本研究は、日本の温帯と冷温帯の沿岸生物群集を対象に、生産者と消費者の広域分散過程、および温度変化に伴う生産者と消費者の相互作用の変異を調べることにより、地球規模での環境変動に伴う沿岸生物群集の変化を理解し、沿岸資源生物および沿岸生態系の保全・管理に資することを目的とする。広域野外調査、リモートセンシング・GISを用いた長期変動解析、メタ群集決定構造の数理的解析、集団遺伝解析、野外操作実験を組み合わせたアプローチにより、沿岸生物群集の構成には、水温等の広域スケールの変動要因と、競争・捕食等の局所スケールの変動要因が複雑に関与していることが判明した。今後の気候変動に伴い、沿岸生物群集の動態は、植物-動物間相互作用の変化を通じて不安定化する可能性が高いことが予測された。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2009年 -2011年 
    代表者 : 灘岡 和夫, 仲岡 雅裕, 練 春蘭, 渡邉 敦
     
    高い生物多様性を有しているにもかかわらず,様々な環境負荷による衰退が深刻になっているCoral Triangle海域の沿岸生態系を対象として,「大気-陸域-沿岸域-海洋」物理流動・水循環統合モデル開発や陸源負荷評価モデル,および炭酸系を含む低次生態系沿岸海洋モデルの開発を行った.また, reef connectivity解明のための集団遺伝学的解析や幼生分散シミュレーションを実施した.これらにより,同海域の沿岸生態系保全・回復に学術面から寄与するスキームを示した.
  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2007年 -2010年 
    代表者 : 仲岡 雅裕, 宮島 利宏, 小松 輝久, 鈴木 孝男, 松政 正俊, 山野 博哉, 堀 正和, 田中 義幸, アユタカ チッチマ, スパンワニッド チャッチャリー, モントム ヤオワルック
     
    本課題は、熱帯沿岸生態系の主要な構成要素である海草藻場を対象に、津波による大規模撹乱と局所的な環境改変の複合効果が生物群集に与える影響を解明する。一連の統合的アプローチにより、津波発生前後の海草藻場の変動パターンが明らかになると共に、津波による効果には、モンスーンや河川水による物質供給パターンの変動や、底生生物による生物撹乱等も複雑に関与していることが明らかになった。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2006年 -2008年 
    代表者 : 仲岡 雅裕, 梶田 忠, 田中 法生, 野田 隆史, 灘岡 和夫, 近藤 昭彦, 熊谷 直喜, 島袋 寛盛, 近藤 昭彦, 灘岡 和夫, 野田 隆史
     
    沿岸生態系の諸機能(生産性、安定性、物質循環など)に多大な影響を与える海草やマングローブなどの優占種(景観形成種)を対象に、生態学、分子生物学、海洋工学、地理情報学の各分野の最先端の理論・方法論・技術を統合的に利用することにより、メタ個体群の広域変動様式および変動機構の一般性、特異性を解明し、主要個体群の生物学的情報、生活史・分散特性に応じた保全指針の作成を行った。
  • 広域多重連成・開放系としての沿岸浅海生態系の劣化の構造解明と保全戦略研究
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2005年 -2007年 
    代表者 : 灘岡 和夫, 茅根 創, 仲岡 雅裕, 浜口 昌巳, 宮澤 泰正
     
    1)石垣島東海岸を対象とした現地調査によって,土壌粒子(赤土)の移流拡散,栄養塩や植物プランクトン等の時空間変動特性,台風等の強風時のリーフ内流動特性やサンゴキャノピー周辺の特徴的な3次元流動構造等を明らかにした.2)サンゴ礁内の局所的な幼生分散過程を解明するべく,石垣島白保海域を対象として現地調査と数値シミュレーション解析を行った.その結果,リーフ周辺でのサンゴ・スリック形成メカニズムを解明するとともに,現地調査結果からアオサンゴ幼生放出やリーフ内幼生密度のピーク時期と潮汐位相等との関係や,幼生の存在水深分布特性等を明らかにした.3)またサンゴキャノピー層効果を取り込んだ3次元リーフ内海水流動モデルならびにそれに基づく幼生分散モデルを新たに開発し,それによって,小潮期に幼生放出が行われることで幼生のリーフ内滞留率が高まり,サンゴキャノピー層内に自己加入する可能性が高くなることを示した.4)同海域に隣接する轟川流域からの陸源負荷量についての長期連続観測を実施するとともに,それに基づいて陸源負荷評価モデルの基本形を構築した.5)オニヒトデに関するマイクロサテライトを開発し,琉球列島周辺を含むインド洋・太平洋の合計23地点でのオニヒトデ集団を対象に集団遺伝学的解析を行うことにより,対象海域の海流規模によって遺伝子流動が大きく規定されることを明らかにした.また,黒潮海域での幼生分散数値シミュレーションを行うことにより,フィリピンから琉球列島,九州,四国,紀伊半島沿岸に至る海域間での非対称的な幼生分散過程を再現し,黒潮を介した2次的大量発生が起きていることを数値シミュレーションと集団遺伝解析の両面から示した.6)サンゴ礁コアによって過去数千年の環境変動の変遷を100年の時間分解能で,マングローブ泥コアによって過去100年の陸域物質流入フラックスの変遷を数年の時間分解能で,サンゴ年輪の解析によって過去100年の環境変動と陸域負荷の変遷を1月の時間分解能で復元することができることを示した.
  • 熱帯海草藻場における生物多様性を指標とした沿岸生態系の機能評価法の開発
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2004年 -2006年 
    代表者 : 仲岡 雅裕, 近藤 昭彦, 小松 輝久, 宮島 利宏, 松政 正俊, 鈴木 孝男, 向井 宏, 野島 哲
     
    タイの熱帯海草藻場を対象に、自然および人為的な環境ストレスが海草藻場の生態系機能と生物多様性に与える影響を解明することにより、海草藻場の生物多様性(種組成および生物量)を指標とした沿岸生態系の機能評価の手法を開発することを目的とする。この目的を達成するため、タイにおける野外調査を3年間行った。得られた成果の概要は下記のとおりである。 1.陸域からの物質流入の程度の異なる2地域5箇所の海草藻場を調査域として、環境条件、生物多様性および生態系機能の長期変動を把握した。海草藻場の物理学的・化学的プロセスは、河川流入のある河口域の海草藻場と、河口から離れた海草藻場で大きく異なること賀判明した。また、海草藻場間の比較では、生物多様性の高い海草藻場ほど生態系機能(生産性および安定性)が高いことが判明した。さらに、これらの変異は、海草の生化学的構成の変化とも相関していることを明らかにした。これらの結果により、海草および付随する動物群集の状態および生物多様性を指標にした海草藻場の生態系機能評価法を検討した。 2.2004年12月に発生した津波による大規模攪乱が海草藻場生態系および生物群集に与える影響を評価した。その結果、海草の種多様性および生物多様性は、津波による攪乱の強度と相関していたのに対し、動物群集のそれは、必ずしも関係しないこと、また海草植生の有無が津波の効果の変異に関連していることが判明した。また堆積物の物理的構造の変化および海草の地下茎の安定同位体比の変化を通じて、津波前後の物理環境の変化を推定し、津波等による堆積物環境の攪乱が生物群集に与える効果の新たな検証方法を確立した。
  • 生物群集の多様性とその決定機構の空間スケール依存性:潮間帯における大規模比較実験
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2002年 -2005年 
    代表者 : 仲岡 雅裕, 野田 隆史, 山本 智子
     
    本研究は、岩礁潮間帯群集を対象に、パッチ群集スケールから地域群集スケールまでを階層的に組み合わせた定量調査・実験を行うことにより、群集の多様性や安定性、およびその決定機構に対する空間スケールの効果を検討することを目的とする。この目的を達成するため、北海道東部から鹿児島県に至る太平洋沿岸の岩礁潮間帯に150調査点を空間の階層性を考慮して設置し、海藻、固着性動物、移動性動物の野外定量調査を行うと共に、環境観測、生物遷移実験、ベントス幼生の加入量の測定を4年間継続した。主な成果は下記のとおりである。 1:空間スケールの変化に伴う種多様性の階層的変異性の違いを明らかにすることを目的とした解析を行った。その結果、種多様性については、地域スケールで明瞭な緯度勾配が見られ、空間スケールの拡大に伴ってγ多様性に対するα多様性の貢献度が相対的に小さくなることが判明した。 2:岩礁潮間帯群集の類似度が異なる空間スケールでどのように変異するか明らかにするために、空間階層サンプリングデザインを用いた調査方法により解析した。その結果、各地域の群集構造は南の2地域を除き有意な違いがあること、また類似度は地理的距離と負の相関があるものの、生物のグループにより距離の効果が異なることが判明した。 3:海藻類を対象にRabinowitzによる希少性分類を適用し、各カテゴリー間で含まれる種の生物学的特徴の違いと、海岸ごとの希少種数と群集の特徴の関係を検討した。その結果、最大のカテゴリーは、希少種の1カテゴリー「地理的分布は広く、生息地の特殊性が低く、個体群密度が低い種」で、全種の約5割を占めた。次いで大きかったカテゴリーは普通種のカテゴリー「地理的分布は広く、生息地の特殊性が低く、個体群密度が高い種」であった。
  • 音響による海底表層の生物・環境3次元マッピングシステムの開発
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2000年 -2002年 
    代表者 : 小松 輝久, 仲岡 雅裕, 平 朝彦, 杉本 隆成, 立川 賢一
     
    正確な船位情報を取得しながらマルチビームソナーを用い,海底の形状と底質の分布,海藻などの生物の分布を測定し,リアルタイムに海底地形を表示しながら,正確な沿岸域の海底のマッピングができる,小型で持ち運びできる海底表層の生物・環境3次元マッピングシステムを開発することを目的に研究を行なった.音響測深機や魚群探知機のように1本のビームによる底深測定では観測線の間隔が広く,観測線の間を補間しなければならない.本研究により開発したシステムは,隙間がなく,補間を必要としない海底表層の3次元的な形状を測量するとともに海底の性質を判別し,海草藻類などのバイオマスをリモートセンシングで測定することが可能である.高性能の衛星測位システム,ジャイロコンパス,動揺センサーにより海底の位置を正確に測量できる.取得されたデータを地理情報システム(GIS)を用いて処理し,海底地形と海底の性質をマッピングする手法も開発した.現場研究は,三陸大槌湾周辺,三浦半島の油壺地先,チュニジア南部ザルジス東方70kmの海台で行なった.大槌湾周辺での調査では,海草藻場を対象として行い,Sea truthとして海草の生態と分布量についても調査した.さらにマッピングソフトウエアの開発に先立って,GISの水産資源分野および海洋学分野への応用に関する研究としてナホトカ号重油汚染による潮間帯生態系の変化や沿岸域保全や管理を対象とした研究も行なった.従来,環境計測に用いられる沿岸域の海底の底質分布や底生生物のバイオマスの測定技術は,現在,古典的なマンパワーにたよるライントランセクト法や観測点における採泥サンプリングなどの非効率的な測定方法しかなかった.開発したシステムは,1-100mの微小スケールの変化に富んだ沿岸生態系をもつ海底環境を詳細に把握できることが確認され,科学的面のみならず沿岸域管理という実際的な社会的面においても貢献できるものと確信する.
  • 熱帯海草藻場の沿岸生態系における機能とその保全に関する研究
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2000年 -2002年 
    代表者 : 小池 勲夫, 向井 宏, 野島 哲, 飯泉 仁, 木暮 一啓, 仲岡 雅裕, 相生 啓子
     
    タイ南部のアンダマン海に面した海草藻場において、陸域からの栄養塩や懸濁粒子の流入、あるいは海岸線の人的改変等が海草藻場の種組成および分布や、藻場生態系の中の底生生物群集に対してどのような影響を与えているかを中心に現地調査を行った。その結果、以下のような研究成果を挙げることが出来た。 (1)卓越する海草の種類が光環境、堆積物の供給量などの外的環境と対応しているかについて解析を行い、種による光合成能力の違い以外に、RhizomeとRootの出し方などの外部形態の違いや光合成生産物の地上部と地下部への配分方法の違いなどが、種の対応性に大きく関与していることが確認された。 (2)窒素、炭素、イオウなどの安定同位体を使って、海草の環境対応性を検討した結果、これらの同位体が海草に対する微妙な環境ストレスの良い指標となることがわかった。 (3)大規模河川の河口から河川流入が全くない海草藻場まで陸域影響の大きく異なる藻場において種組成や生物量を計測した所、河川の影響が強くなるに従って種組成、生物量とも減少し、これらがこの海域においては負の影響を持っていることが推測された。 (4)藻場に対する光環境を強く支配する堆積物の再懸濁プロセスを現場観測で解析し、陸からの流入懸濁物、潮汐および風波の3つの要因が、小規模の海草藻場でも地形その他の影響を受けて、大きく個々の物理的営力の効果が違っていることがわかった。またその違いは藻場の種組成のみならず、底生生物の活性にも大きな影響を与えていることが推測された。 (5)海草が主な餌であるジュゴンがどのような種類の海草をより好んで食べるかについてフィールド調査を行い、このタイ南部の海域で摂餌はが最も盛んなのは、Halophila藻場であることが確認された。この藻場は土砂流入などの環境変動を最も受けやすい種なので、その藻場の保全がジュゴンの生息環境としても重要である。
  • 陸と海との相互作用―陸上生態系の人為的改変と沿岸生態系の応答―
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2001年 -2001年 
    代表者 : 小池 勲夫, 小松 輝久, 柳 哲雄, 向井 宏, 仲岡 雅裕, 茅根 創
     
    本研究では、わが国の環境問題を理解する上で極めて重要な課題でありながらこれまで殆ど研究の行われていなかった陸域と沿岸域の相互作用について総合的に研究するため、研究グループの組織および各研究グループでの研究手法のすり合わせ、および具体的な研究フィールドの選択について調査を行い、「特定研究領域」として申請するための準備を行った。具体的には平成13年8月に関連研究者により研究フィールド選定のための視察を北海道の厚岸周辺で行うとともに、研究計画立案のための打ち合わせ会議を北大厚岸臨海実験所で開いた。さらに同年10月に具体的な研究計画を詰めるための会合を東大海洋研究所で開き、さらに、本研究領域参加メンバーが主体となった公開シンポジウム森と海の相互作用(東京大学海洋研究所共同利用シンポジュム 平成13年10月4-5日)を開催し、研究者および一般市民を対象にこの問題全般においてのこれまでの取り組みの成果および今後の研究指針についての論議を行った。このような準備段階を経て特定領域研究申請書海と陸の相互作用に関する研究--地域・海域環境の総合的な理解を目指して--が本研究課題代表者によって作成され提出することが出来た。本研究は陸上生態系と沿岸生態系の相互作用を、1)これまで予察的な研究が進んでいるわが国の2つの水系による中核拠点観測・研究、2)全国の森林、河川、沿岸データを集積・補強して陸上生態系との利用形態と沿岸との比較研究、3)大都市域の流域で自然科学と社会科学との共同研究で自然環境とと人間活動との共生を目指す研究を3つの柱として行う。この領域研究全体に共通する視点は、河川の集水域とその沿岸域を1つのユニットとし「集水域大生態系」と考えて研究を実施する点である。又、物質のユニット内での輸送は1)物理プロセス、2)生物プロセスの2つに分離してその特性を解析する予定である。
  • 海草混合群落の空間構造の変動に対する栄養成長と種子繁殖の相対的重要性の解明
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1999年 -2000年 
    代表者 : 仲岡 雅裕
     
    本研究では、海草藻場の空間構造の変動に対する海草の栄養成長と種子繁殖の効果を、定量調査、野外実験およびモデル解析により明らかにすることを目的とする。本年度は下記の項目について成果が得られた。 1:海草藻場の空間構造と動態の定量的解明:前年度に設置した岩手県大槌湾・船越湾の海草藻場調査域において、主要構成種であるアマモとタチアマモの動態を解析した結果、種子生産量、種子埋土量および実生の発芽率はアマモの方が高いことが判明した。これは、撹乱により生じたギャップにアマモが先に侵入しやすいことを示するが、海草藻場の追跡調査によってもこの点が確認された。また、栄養生長については、光資源の少ない深い水深帯に生育するタチアマモが、浅い水深帯のアマモと同等の一次生産量を持つことが明らかになった。 2:種間相互作用に関する実験的解析:アマモとタチアマモの移植実験を行った結果、水深帯により種間相互作用の様式が異なることを示すデータが得られた。この変異には光・栄養塩・撹乱の各要因が複合的に関与していることが示唆された。また、植食性動物の効果について、種子食者であるタナイスの摂食量を室内実験で検討した結果、タチアマモに対する影響が強いことが確認され、前年度に示した両種の種子食害率の変異をもたらす要因が解明された。 3:モデルによる海草藻場空間構造の動態解析:以上のデータに基づいて海草2種の動態をシミュレーションモデルにより解析したところ、空間構造および種子繁殖量の変異の効果を取り入れることにより、両種の共存する水深帯が拡大することが予想された。この結果は、実際の海草藻場における両種の分布と一致しており、両種の共存において、海草藻場の空間構造と、種による栄養成長と種子繁殖の相対的重要性の変異が重要であることが明らかになった。
  • 二枚貝とヒドロゾアの相互作用の可塑性に関する実験生態学的・個体群統計学的研究
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1997年 -1998年 
    代表者 : 仲岡 雅裕
     
    本研究は、付着性のヒドロ虫類(カタテニンギョウ)と宿主である二枚貝キララガイについて、両種の相互作用の経時的変化を定量的に評価することを目的とする。今年度の成果は下記の通りである。 1、 野外調査:岩手県大槌湾でキララガイの採集を行い、カタテニンギョウの付着率を計測した。今年度はキララガイの新規加入がなかったため、キララガイの平均サイズは増加した。これに伴いカタテニンギョウの付着率も減少した。この結果は、前年度確認されたカタテニンギョウのサイズ依存的付着率からの予測と一致した。 2、 野外実験:春季にキララガイを標識後埋設し、カタテニンギョウの有無による生長量、生存率の変異を検定した。その結果、カタテニンギョウの有無に伴うキララガイの成長量、生存率に有意な差は見られなかった。この結果は前年度行った夏季、秋季の結果と同じであり、両種の相互作用に著しい季節変異がないことを示している。 3、 室内実験:キララガイの捕食者である十脚類数種には、カタテニンギョウの付着の有無に伴うキララガイへの攻撃率に変異は検出されかった。 4、 個体群統計解析:上記で得られたデータを用い、以下の解析を行った。 (1), キララガイの加入の変動がカタテニンギョウ群集に与える影響:確率論的行列モデルを用いた解析では、キララガイの新規加入の経年変動が大きいほど、両種の共存条件が厳しくなることが判明した。これは前年度解析した決定論的モデルの予測とは異なった。 (2), カタテニンギョウがキララガイに与える影響:行列モデルによる解析の結果、カタテニンギョウが付着したキララガイの適応度の減少は1%以下であった。両者の相互作用は、カタテニンギョウの片利共生と結論された。
  • 岩手県船越湾における海草藻場・タチアマモ群落の構造と葉上動物群集の解析
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 1996年 -1998年 
    代表者 : 相生 啓子, 小松 輝久, 仲岡 雅裕
     
    (1) 船越湾および大槌湾の海草藻場の分布と面積を把握するため、タチアマモの花株の最盛期にあたる6月に精密小型音響測深機による船上からの探査を行った。船越湾では、吉里吉里港内の水深3〜4mのギャップに、アマモとタチアマモがモザイク状に群落を形成している。東西方向に設置したトランセクト・ラインに添って、ライン上の海草の出現状況についての詳細なセンサスを行った。アマモおよびタチアマモ群落内は、安定した砂泥底があり、草高は潮位によって決められることが示唆された。水中光量子の分布プロファイルから、港外のタチアマモ群落の水深16m付近の光条件が、分布の限界の要因になっていることが示唆された。船越湾におけるタチアマモ群落の立地条件は、透明度が高く低い海水温、緩く傾斜した斜面のような海底地形によるものであると考えられる。 (2) タチアマモの花株の花穂の生長は6月頃開始し、種子が成熟し、花穂が落下し終るのが8月末である。その後も花株は6〜7mの長いまま生きていて、11月末頃枯れる。前年の冬から春にかけて、花株本体が伸長し始めるので、枯死するまでの期間は1年半以上かかることが示唆された。タチアマモの花株の生長期間が長いのは、年間を通じ海水温度が、冬期3〜5度、夏期18〜20度と寒冷域にあることと、光環境との相互作用によるものと考えられる。 (3) タチアマモの葉上動物群集に関しては、巻貝を中心に定量採集を行い、個体群の動態を調査した。葉上性巻貝の優占種は、アコヤシタダミとコムラサキバイである。アコヤシタダミが海草種・アマモあるいはタチアマモのいずれか一方に特異的に依存する繁殖特性を示すことは無かった。アコヤシタダミは、アマモに適応的な繁殖特性が見られた。
  • 海草群落に生息する葉上藻食性巻貝と海草の相互作用に関する実験生態学的研究
    日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 1996年 -1996年 
    代表者 : 仲岡 雅裕
     
    本研究では野外調査および実験により、海草類と葉上藻食性巻貝類の相互関係について、以下の新たな知見が得られた。 1.藻食性巻貝の個体数変動の要因について: 調査地である岩手県大槌湾および船越湾の海草葉上巻貝の中の優占種であるアコヤシタダミとコムラサキバイ2種に注目し、海草2種(アマモとタチアマモ)の葉上における季節変動と基質間変異を調査した。その結果、(1)巻貝両種とも海草の現存量および水温が最大になる夏に、新規加入に伴い個体数が増加し、夏から秋にかけて個体数が減少すること、(2)アコヤシタダミの密度は海草2種間で変異がないが、コムラサキバイではアマモ葉上のほうが密度が高いこと、が明らかになった。餌となる付着藻類は春から夏にかけて急減することから、餌量が巻貝の個体数の減少要因になっていることが示唆された。室内実験の結果、(3)巻貝類には餌をめぐる種内・種間競争が存在し、これが、個体数の季節変動、基室間変異に大きな影響を与えていること、(4)巻貝の海草2種に対する選好性には変異がなく、従ってコムラサキバイに見られた基質間変異は、海草の質によるものではなく、海草2種の群落間の環境要因に存在していることが示された。また、野外実験の結果、(5)巻貝の個体数変異に海草の立体構造が有意な効果を与えている証拠は得られなかった。 2.海草および付着藻類に対する藻食性巻貝の影響: 野外調査および室内実験の結果、巻貝の密度は付着藻類の量に負の効果を与えるものの、海草自身の成長、現存量の変化に対する有意な効果は検出できなかった。これらのデータを利用して求めた数理モデルは広い密度領域での3者の共存を予測した。室内実験は夏にのみ行われたため、今後は種間関係の季節的な変異を明らかにすることが必要と思われる。

教育活動情報

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    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 生物多様性、進化生態学、適応、生物間相互作用、被食防衛系、昆虫生態学、群集生態学、生態系機能 biodiversity, evolutionary ecology, adaptation, biological interaction, defensive system, pollination system, ecological entomology, community ecology, ecosystem function
  • 生物圏科学特別講義Ⅱ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : Aquatic Biology, Marine Ecology, Oceanography
  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Marine ecosystem, biodiversity, biological community, hydrodynamics, seagrass beds, kelp forest, statistical data analyses, cold current system
  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Seagrass bed, seaweed bed, kelp forest, biodiversity, plant-animal interactions, eco-physiology, statistical data analyses, cold current system
  • フィールド科学特別実習Ⅰ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : フィールド科学、森林圏、水圏、耕地圏、生物学、生態学、資源・生態系管理 field science, forest ecosystem, aquatic ecosystem, agricultural ecosystem, biology, ecology, resource and ecosystem management
  • フィールド科学特別実習Ⅱ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : フィールド科学、森林圏、水圏、耕地圏、生物学、生態学、資源・生態系管理 field science, forest ecosystem, aquatic ecosystem, agricultural ecosystem, biology, ecology, resource and ecosystem management
  • 水圏科学特論Ⅰ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 水圏生物 藻類 海草類 プランクトン 細胞 発生 環境適応 生理生態学 群集生態学 生態系生態学
  • 大学院共通授業科目(一般科目):自然科学・応用科学
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : Global Ocean, resources, economy, sustainability, resilience. clean energy, remediation, adaptation, conservation, UN Development Goals
  • 自然史科学特別講義Ⅲ
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 理学院
    キーワード : Global Ocean, resources, economy, sustainability, resilience. clean energy, remediation, adaptation, conservation, UN Development Goals
  • 科学・技術の世界(1単位)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 現代生物科学,21世紀に生物科学が解決しなければならない課題,生物の多様性,系統,進化,生物の形態,生命活動の多様性
  • 海洋生態学実習
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 厚岸臨海実験所、海洋生態学、プランクトン、ベントス、アマモ場、岩礁潮間帯群集
  • 海洋生態学実習
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 理学部
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 北海道東部、別寒辺?川、森林、河川、湿原、汽?、海洋、?態系のつながり、フィールドワーク、?物多様性、?態系機能
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 森林、河川、沿岸生態系、相互作用、構造、物質循環、生物多様性、自然景観
  • 一般教育演習(フレッシュマンセミナー)
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : フィールド、体験型、環境科学、自然、産業
  • 野外巡検
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : フィールド実習, 野外観察, 生物相, 生態学

大学運営

学内役職歴

  • 2020年4月1日 - 2022年3月31日 北方生物圏フィールド科学センター 副センター長

委員歴

  • 2018年01月 - 2019年12月   日本生態学会   Ecological Research編集長
  • 2016年01月 - 2017年12月   日本生態学会   Ecological Research副編集長


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