研究者データベース

平譯 享(ヒラワケ トオル)
水産科学研究院 海洋生物資源科学部門 海洋計測学分野
准教授

基本情報

所属

  • 水産科学研究院 海洋生物資源科学部門 海洋計測学分野

職名

    准教授

学位

  • 理学博士 (名古屋大学)

メールアドレス

    eメール:    hirawake@fish.hokudai.ac.jp

ホームページURL

研究キーワード

  • 海洋生態系   生物生産   植物プランクトン   海洋環境   極域海洋   低温   生物多様性   チャクチ海   ベーリング海   北極海   極球海洋   海氷   南極海   環境変動   海洋生態   極地   高緯度海域   地球規模   春季ブルーム   海氷生態系   海洋光学   衛星海色リモートセンシング   衛星海洋学   海洋基礎生産   

研究分野

  • 環境学 / 環境動態解析
  • 水産学 / 水産学一般
  • 環境学 / 環境影響評価・環境政策
  • 環境学 / 環境動態解析

職歴

  • 2007年04月 - 現在  北海道大学大学院・水産科学研究院准教授
  • 1998年04月 - 2007年03月  国立極地研究所助手・助教

所属学協会

  • 米国海洋学会   日本海洋学会   日仏海洋学会   水産海洋学会   

研究活動情報

論文

  • Isada Tomonori, Hirawake Toru, Nakada Satoshi, Kobayashi Tsukuru, Sasaki Ken'ichi, Tanaka Yoshiyuki, Watanabe Shuichi, Suzuki Koji, Saitoh Sei-Ichi
    ESTUARINE COASTAL AND SHELF SCIENCE 188 199 - 211 0272-7714 2017年03月 [査読有り][通常論文]
  • Tokuhiro Koki, Abe Yoshiyuki, Matsuno Kohei, Onodera Jonaotaro, Fujiwara Amane, Harada Naomi, Hirawake Toru, Yamaguchi Atsushi
    POLAR SCIENCE 19 94 - 111 1873-9652 2019年03月 [査読有り][通常論文]
  • Kostadinov Tihomir S., Cabre Anna, Vedantham Harish, Marinov Irina, Bracher Astrid, Brewin Robert J. W., Bricaud Annick, Hirata Takafumi, Hirawake Toru, Hardman-Mountford Nick J., Mouw Colleen, Roy Shovonlal, Uitz Julia
    REMOTE SENSING OF ENVIRONMENT 190 162 - 177 0034-4257 2017年03月 [査読有り][通常論文]
  • Alabia Irene D., Molinos Jorge Garcia, Saitoh Sei-Ichi, Hirawake Toru, Hirata Takafumi, Mueter Franz J.
    DIVERSITY AND DISTRIBUTIONS 24 (11) 1583 - 1597 1366-9516 2018年11月 [査読有り][通常論文]
  • Syah Achmad Fachruddin, Saitoh Sei-Ichi, Alabia Irene D., Hirawake Toru
    3RD INTERNATIONAL SYMPOSIUM ON LAPAN-IPB SATELLITE FOR FOOD SECURITY AND ENVIRONMENTAL MONITORING 2016 54 1755-1307 2017年 [査読有り][通常論文]
  • Fujiwara Amane, Nishino Shigeto, Matsuno Kohei, Onodera Jonaotaro, Kawaguchi Yusuke, Hirawake Toru, Suzuki Koji, Inoue Jun, Kikuchi Takashi
    POLAR BIOLOGY 41 (6) 1279 - 1295 0722-4060 2018年06月 [査読有り][通常論文]
  • Shigeto Nishino, Takashi Kikuchi, Amane Fujiwara, Toru Hirawake, Michio Aoyama, Michio Aoyama
    Biogeosciences 13 (8) 2563 - 2578 17264170 2016年04月 [査読有り][通常論文]
     
    © Author(s) 2016.We analysed mooring and ship-based hydrographic and biogeochemical data obtained from a Hope Valley biological hotspot in the southern Chukchi Sea. The moorings were deployed from 16 July 2012 to 19 July 2014, and data were captured during spring and autumn blooms with high chlorophyll a concentrations. Turbidity increased and dissolved oxygen decreased in the bottom water at the mooring site before the autumn bloom, suggesting an accumulation of particulate organic matter and its decomposition (nutrient regeneration) at the bottom. This event may have been a trigger for the autumn bloom at this site. The bloom was maintained for 1 month in 2012 and for 2 months in 2013. The maintenance mechanism for the autumn bloom was also studied by hydrographic and biogeochemical surveys in late summer to autumn 2012 and 2013. Nutrient-rich water from the Bering Sea supplied nutrients to Hope Valley, although a reduction in nutrients occurred in 2012 by the influence of lower-nutrient water that would have remained on the Chukchi Sea shelf. In addition, nutrient regeneration at the bottom of Hope Valley could have increased nutrient concentrations and explained 60ĝ€% of its nutrient content in the bottom water in the autumn of 2012. The high nutrient content with the dome-like structure of the bottom water may have maintained the high primary productivity via the vertical nutrient supply from the bottom water, which was likely caused by wind-induced mixing during the autumn bloom. Primary productivity was 0.3ĝ€gĝ€Cĝ€mĝ'2ĝ€dĝ'1 in September 2012 and 1.6ĝ€gĝ€Cĝ€mĝ'2ĝ€dĝ'1 in September 2013. The lower productivity in 2012 was related to strong stratification caused by the high fraction of surface sea ice meltwater.
  • Natsuike Masafumi, Matsuno Kohei, Hirawake Toru, Yamaguchi Atsushi, Nishino Shigeto, Imai Ichiro
    HARMFUL ALGAE 61 80 - 86 1568-9883 2017年01月 [査読有り][通常論文]
  • Natsuike Masafumi, Saito Rui, Fujiwara Amane, Matsuno Kohei, Yamaguchi Atsushi, Shiga Naonobu, Hirawake Toru, Kikuchi Takashi, Nishino Shigeto, Imai Ichiro
    PLOS ONE 12 (11) 1932-6203 2017年11月 [査読有り][通常論文]
  • Mouw Colleen B., Hardman-Mountford Nick J., Alvain Severine, Bracher Astrid, Brewin Robert J. W., Bricaud Annick, Ciotti Aurea M., Devred Emmanuel, Fujiwara Amane, Hirata Takafumi, Hirawake Toru, Kostadinov Tihomir S., Roy Shovonlal, Uitz Julia
    FRONTIERS IN MARINE SCIENCE 4 2017年 [査読有り][通常論文]
  • Alabia Irene D., Dehara Mariko, Saitoh Sei-Ichi, Hirawake Toru
    REMOTE SENSING 8 (11) 2072-4292 2016年11月 [査読有り][通常論文]
  • Zhang Xun, Saitoh Sei-Ichi, Hirawake Toru
    INTERNATIONAL JOURNAL OF REMOTE SENSING 38 (21) 6129 - 6146 0143-1161 2017年 [査読有り][通常論文]
  • Landeira Jose M., Matsuno Kohei, Yamaguchi Atsushi, Hirawake Toru, Kikuchi Takashi
    POLAR BIOLOGY 40 (9) 1805 - 1819 0722-4060 2017年09月 [査読有り][通常論文]
  • Achmad F. Syah, Achmad F. Syah, Sei Ichi Saitoh, Sei Ichi Saitoh, Irene D. Alabia, Toru Hirawake
    Fishery Bulletin 114 (3) 330 - 342 00900656 2016年06月 [査読有り][通常論文]
     
    © 2016, National Marine Fisheries Service. All rights reserved.Fishing locations for Pacific saury (Cololabis saira) obtained from images of the Operational Linescan System (OLS) of the U.S. Defense Meteorological Satellite Program, together with maximum entropy models and satellite-based oceanographic data of chlorophylla concentration (chl-a), sea-surface temperature (SST), eddy kinetic energy (EKE), and sea-surface height anomaly (SSHA), were used to evaluate the effects of oceanographic conditions on the formation of potential fishing zones (PFZ) for Pacific saury and to explore the spatial variability of these features in the western North Pacific. Actual fishing regions were identified as the bright areas created by a 2-level slicing method for OLS images collected August-December during 2005-2013. The results from a Maxent model revealed its potential for predicting the spatial distribution of Pacific saury and highlight the use of multispectral satellite images for describing PFZs. In all monthly models, the spatial PFZ patterns were explained predominantly by SST (14-16°C) and indicated that SST is the most influential factor in the geographic distribution of Pacific saury. Also related to PFZ formation were EKE and SSHA, possibly through their effects on the feeding grounds conditions. Concentration of chl-a had the least effect among other environmental factors in defining PFZs, especially during the end of the fishing season.
  • Waga Hisatomo, Hirawake Toru, Fujiwara Amane, Kikuchi Takashi, Nishino Shigeto, Suzuki Koji, Takao Shintaro, Saitoh Sei-Ichi
    REMOTE SENSING 9 (3) 2072-4292 2017年03月 [査読有り][通常論文]
  • Irene D. Alabia, Sei Ichi Saitoh, Sei Ichi Saitoh, Toru Hirawake, Hiromichi Igarashi, Yoichi Ishikawa, Norihisa Usui, Masafumi Kamachi, Toshiyuki Awaji, Masaki Seito
    Hydrobiologia 772 (1) 215 - 227 00188158 2016年06月 [査読有り][通常論文]
     
    © 2016, Springer International Publishing Switzerland.The effects of the El Niño Southern Oscillation (ENSO)-mediated environmental changes to marine resources were long recognized; however, species-specific responses were also reported to vary, possibly more so, under the emerging event-to-event diversity of the ENSO conditions. Hence, the objective of this study is to characterize the potential impacts of the ENSO-regulated environmental variability to squid habitat in the central North Pacific under the different ENSO flavors, using habitat models developed from at least a decade of fishery-dependent dataset and environmental parameters. Our findings revealed that the potential squid habitats were largely influenced by ENSO-forced environmental changes during the squid’s spawning and nursery periods, resulting in substantial reduction/enhancement of available habitats in the succeeding summers of Central Pacific El Niño/La Niña, where the latter led to an expansion of favorable spawning and nursery grounds. However, the autumn–winter periods of weaker and short-lived Eastern Pacific El Niño showed elevated potential habitats due to minimal sea surface temperature drop and close proximity of spawning and nursery grounds to optimal feeding environments. The quick, albeit variable, squids’ responses to ENSO flavors accentuate their promising potential as ecological beacons under climate changes, aiding the development of adaptive management strategies for commercially exploited fisheries.
  • Kohei Matsuno, Jose M. Landeira Sanchez, Atsushi Yamaguchi, Toru Hirawake, Takashi Kikuchi
    Polar Science 10 (3) 335 - 345 18739652 2015年07月 [査読有り][通常論文]
     
    © 2016.From July to August 2007 and June to July 2008, the horizontal/geographical changes in the zooplankton community in the Bering and Chukchi Seas were studied. The geographical patterns, which were common for these two years, were observed for salinity, chlorophyll a (Chl. a), zooplankton chaetognaths, hydrozoans and the whole zooplankton community. Among them, the patterns of salinity and Chl. a were related with the horizontal distribution of the water masses. The distributions of the two carnivorous taxa were correlated with their prey (copepods or barnacle larvae). The analysis of the structural equation model (SEM) revealed that the horizontal distribution of the zooplankton abundance and biomass were governed by the different taxa. Thus, the zooplankton abundance was governed by the numerically dominant but smaller-bodied taxa, such as the barnacle larvae and copepod Pseudocalanus spp., while the zooplankton biomass was determined by the large-bodied copepods, such as Calanus glacialis/. marshallae and Eucalanus bungii.
  • Mega Syamsuddin, Sei Ichi Saitoh, Toru Hirawake, Fadli Syamsudin, Mukti Zainuddin
    International Journal of Remote Sensing 37 (9) 1 - 14 01431161 2016年01月 [査読有り][通常論文]
     
    © 2016 Taylor & FrancisRemotely derived environmental variables, including sea surface height anomaly (SSHA), sea surface temperature (SST), chlorophyll-a (chl-a), eddy kinetic energy (EKE), mixed layer data set of argo float (MLD), Niño 3.4 index, and bigeye tuna catch data for the period 1997–2008, were used to analyse ocean climate variability and how they relate to the hotspots of bigeye tuna catch in the eastern Indian Ocean off Java. The empirical orthogonal function (EOF) was performed to obtain a more detailed structure of the spatio-temporal ocean variability in the region. The results showed that the first EOF modes of chl-a, SSHA, and SST accounted for 42.8%, 36.5%, and 27.4% of total variance, respectively, and these corresponded to the interannual signal. The maps of spatial patterns of the first EOF modes of SSHA, SST, and chl-a gave very typical values for cold-water SSHA, low SST, and high chl-a concentration along the southern coast of the Indonesian archipelago; and warm-water SSHA, high SST, and low chl-a concentration in the offshore region to make frontal areas along the latitudinal line around 10–12º S. The EOF analysis further revealed a strong relationship between the El Niño event and favourable oceanographic conditions, resulting in a significant increase in bigeye tuna catch. The average hook rate of 0.71 (0.43) was recorded during El Niño (La Niña). Major hotspots were located away from the confluence region and frontal areas around 11–16° S and 110–118° E and were thus demonstrated as the most favourable oceanographic conditions for bigeye tuna fishing in the eastern Indian Ocean off Java.
  • Lee YJ, Matrai PA, Friedrichs MA, Saba VS, Antoine D, Ardyna M, Asanuma I, Babin M, Bélanger S, Benoît-Gagné M, Devred E, Fernández-Méndez M, Gentili B, Hirawake T, Kang SH, Kameda T, Katlein C, Lee SH, Lee Z, Mélin F, Scardi M, Smyth TJ, Tang S, Turpie KR, Waters KJ, Westberry TK
    Journal of geophysical research. Oceans 120 (9) 6508 - 6541 2169-9275 2015年09月 [査読有り][通常論文]
  • Tanaka K, Takesue N, Nishioka J, Kondo Y, Ooki A, Kuma K, Hirawake T, Yamashita Y
    Scientific reports 6 34123  2045-2322 2016年09月 [査読有り][通常論文]
  • 松本 健太郎, 有馬 大地, 松野 孝平, 山﨑 康裕, 大西 広二, 大木 淳之, 平譯 享, 山口 篤, 今井 一郎
    北海道大学水産科学研究彙報 北海道大学水産科学研究彙報 66 (1) 29 - 38 1346-1842 2016年03月 [査読無し][通常論文]
     
    The spring phytoplankton community in the western North Pacific is characterized by large variability in both the horizontal and verical dimensions. To evaluate this variability, phytoplankton communitiesat 39°30'N-44°00'N along 155°E were investigated in situ using a multi-excitation fluorometer during May 2014. The sea surface chlorophyll a(Chi. a) level was high and composed mainly of diatoms near 43°30'N-42'N, while it was low and composed of dinoflagellates south of 40°N. Based on seven fixed-station investigations, the phytoplanklton communities were classified into 4 types : a low Chl. a level before bloom (44°N), massive diatom bloom(42°N-43°N), low Chl. a level with dinoflagellates(40°N-41°N) and lowest Chl.a(at the southernmost station at 39°30'N). These phytoplankton communities corresponded with the formation of a water mass separating the Subartctic front(SAF) and Subarctic boundary(SAB). Multi-excitation fluorometry data showed a high correlation with Chl. a measurements obtained via Thrmo-salinometer and biovolume microscopic analyses(r²=0.67-0.97,p<0.05). Thus, we concluded that a multi-excitation fluorometer can be applied for the evaluation of detailed spatial and temporal changes in the phytoplankton community at various locations.
  • Tomonori Isada, Toru Hirawake, Tsukuru Kobayashi, Yuichi Nosaka, Masafumi Natsuike, Ichiro Imai, Koji Suzuki, Koji Suzuki, Sei Ichi Saitoh
    Remote Sensing of Environment 159 134 - 151 00344257 2015年03月 [査読有り][通常論文]
     
    © 2014 Elsevier Inc. Identification of phytoplankton functional groups is key to understanding marine biogeochemical cycles. For more accurate understanding of phytoplankton community structure and its implications for ocean color remote sensing applications, we investigated seasonal changes in phytoplankton pigments with high-performance liquid chromatography (HPLC), hyperspectral absorption coefficients of detritus (ad(λ)), phytoplankton (aph(λ)), and colored dissolved organic matter (aCDOM(λ)), and hyperspectral aph(λ) derived from remote sensing reflectance (aph_Rrs-derived(λ)) in the coastal waters of Funka Bay from 2010 to 2012. Chlorophyll a (Chl a) concentrations measured by HPLC ranged from 0.29 to 8.6mgm-3. Phytoplankton community compositions, as estimated by chemotaxonomic analysis (CHEMTAX) based on HPLC phytoplankton pigments, showed a seasonal succession of diatoms, chlorophyll b-containing phytoplankton (chlorophytes and prasinophytes), and cyanobacteria. Additionally, to identify the dominant type of phytoplankton with an alternative technique to CHEMTAX analysis, we employed a derivative spectroscopy/similarity index (SI) approach for aph(λ) as an optical detection technique for discriminating between different types of phytoplankton. In particular for diatom-dominated stations, SI values relative to the second derivative spectra of aph(λ) of diatom cultures, isolated from our study region, were significantly higher than those for chlorophyll b-containing phytoplankton- and cyanobacteria-dominated stations. Furthermore, we found a strong relationship between the SI values calculated from the second derivative spectra and the composition of diatoms as estimated by CHEMTAX. These results suggest that the two different methods validated each other's performance and precision in estimating relative diatom abundance from bulk samples and that it is possible to optically discriminate the dominance of diatoms using derivative spectra of aph(λ). We extended this combination approach to hyperspectral aph_Rrs-derived(λ), using a quasi-analytical algorithm within 400-546nm range. We found a significant correlation between SI values obtained from the second derivative spectra of aph_Rrs-derived(λ)/aph_Rrs-derived(443) and the composition of diatoms derived by CHEMTAX, but it was not as high as for aph(λ) measured by filter-pad analysis. These results indicate that using hyperspectral optical data of aph(λ) and Rrs(λ) with derivative spectroscopy is potentially a promising approach to identify seasonal variability in the composition of diatoms in coastal waters. Furthermore, a hyperspectral approach in combination with CHEMTAX analysis as a reference for phytoplankton community structure has proven useful in improving our understanding of phytoplankton community structure in the coastal waters of Funka Bay.
  • Yang Liu, Sei Ichi Saitoh, Sei Ichi Saitoh, Yu Ihara, Satoshi Nakada, Makoto Kanamori, Xun Zhang, Katsuhisa Baba, Yoichi Ishikawa, Toru Hirawake, Toru Hirawake
    ICES Journal of Marine Science 72 (9) 2684 - 2699 10543139 2015年01月 [査読有り][通常論文]
     
    © 2015 International Council for the Exploration of the Sea. All rights reserved.The Japanese scallop (Patinopecten (Mizuhopecten) yessoensis) is an important commercial species in Funka Bay, Japan, where it is farmed using the hanging culture method. Our study was based on 6 years (from 2006 to 2011) of monthly in situ observations of scallop growth at Yakumo station. To produce a basic spatial distribution dataset, we developed an interpolation solution for the shortage of Chl- A concentration data available from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite. Additionally,we integrated four-dimensional variational (4D-VAR) assimilation water temperature data from ocean general circulation models (OGCMs), with four vertical levels (6, 10, 14, and 18 m) from the sea surface. Statistical models, including generalized additive models (GAMs) and generalized linear models, were applied to in situ observation data, satellite data, and 4D-VARdata to identify the influence of environment factors (interpolated Chl-a, temperature, and depth) on the growth of scallops, and to develop a three-dimensional growth prediction model for the Japanese scallops in Funka Bay. We considered three methods to simulate the growth process of scallops (accumulation, summation, and product), and used them to select the most suitable model. All the interpolated Chl- A concentrations and 4D-VAR temperature data were verified by shipboard data. The results revealed that GAM, using an accumulation method that was based on a combination of integrated temperature, integrated log Chl-a, depth, and number of days, was best able to predict the vertical and spatial growth of the Japanese scallop. The predictions were verified by in situ observations from different depths (R2 = 0.83- 0.94). From the distribution of three-dimensional predicted scallop growth maps at each depth, it was suggested that the growth of the Japanese scallop was most favourable at 6 m and least favourable at 18 m, although variations occurred in each aquaculture region in different years. These variations were probably due to the ocean environment and climate variation.
  • Kohei Matsuno, Atsushi Yamaguchi, Toru Hirawake, Shigeto Nishino, Jun Inoue, Takashi Kikuchi
    Polar Biology 38 (7) 1075 - 1079 07224060 2015年02月 [査読有り][通常論文]
     
    © 2015 Springer-Verlag Berlin Heidelberg The species composition of Arctic zooplankton differs greatly from that of the zooplankton of the North Pacific and Bering Sea. Particularly with greater warming from sea-ice retreat, the reproduction of North Pacific species transported into the Chukchi Sea and beyond may lead to changes in the Arctic pelagic ecosystem. We report the egg production and hatching of the Pacific copepod Neocalanus flemingeri in the Chukchi Sea based on shipboard experiments performed in September 2013. The reproductive capability of N. flemingeri observed in the Chukchi Sea resembled that reported in the Pacific, with the exception of a lower hatching success. Only 7.5 % of N. flemingeri eggs hatched compared with 93 % in Pacific experiments. Low hatching success is considered to be caused by failures of fertilization. The potential recruitment number for N. flemingeri suggests that it is unlikely to establish expatriate Arctic populations in the near future.
  • Shigeto Nishino, Yusuke Kawaguchi, Yusuke Kawaguchi, Jun Inoue, Jun Inoue, Toru Hirawake, Amane Fujiwara, Amane Fujiwara, Ryosuke Futsuki, Jonaotaro Onodera, Michio Aoyama, Michio Aoyama
    Journal of Geophysical Research C: Oceans 120 (3) 1975 - 1992 21699275 2015年03月 [査読有り][通常論文]
     
    © 2015. American Geophysical Union. All Rights Reserved. A fixed-point observation station was set up in the northern Chukchi Sea during autumn 2013, and for about 2 weeks conductivity-temperature-depth (CTD)/water samplings (6 h) and microstructure turbulence measurements (2 to 3 times a day) were performed. This enabled us to estimate vertical nutrient fluxes and the impact of different types of turbulent mixing on biological activity. There have been no such fixed-point observations in this region, where incoming low-salinity water from the Pacific Ocean, river water, and sea-ice meltwater promote a strong pycnocline (halocline) that stabilizes the water column. Previous studies have suggested that because of the strong pycnocline, wind-induced ocean mixing could not change the stratification to impact biological activity. However, the present study indicates that a combined effect of an uplifted pycnocline accompanied by wind-induced inertial motion and turbulent mixing caused by intense gale-force winds (>10 m s-1) did result in increases in upward nutrient fluxes, primary productivity, and phytoplankton biomass, particularly large phytoplankton such as diatoms. Convective mixing associated with internal waves around the pycnocline also increased the upward nutrient fluxes and might have an impact on biological activity there. For diatom production at the fixed-point observation station, it was essential that silicate was supplied from a subsurface silicate maximum, a new feature that we identified during autumn in the northern Chukchi Sea. Water mass distributions obtained from wide-area observations suggest that the subsurface silicate maximum water was possibly derived from the ventilated halocline in the Canada Basin.
  • A. Fujiwara, T. Hirawake, K. Suzuki, L. Eisner, I. Imai, S. Nishino, T. Kikuchi, S. I. Saitoh
    Biogeosciences 13 115 - 131 17264170 2016年01月 [査読無し][通常論文]
     
    © 2016 Author(s).The size structure and biomass of a phytoplankton community during the spring bloom period can affect the energy use of higher-trophic-level organisms through the predator-prey body size relationships. The timing of the sea ice retreat (TSR) also plays a crucial role in the seasonally ice-covered marine ecosystem, because it is tightly coupled with the timing of the spring bloom. Thus, it is important to monitor the temporal and spatial distributions of a phytoplankton community size structure. Prior to this study, an ocean colour algorithm was developed to derive phytoplankton size index L, which is defined as the ratio of chlorophyll/Emphasis (chl
  • Yang Liu, Sei Ichi Saitoh, Satoshi Nakada, Xun Zhang, Toru Hirawake
    Sustainability (Switzerland) 7 (2) 1263 - 1279 20711050 2015年01月 [査読有り][通常論文]
     
    © 2015 by the authors. We provide an overview of selected recent operational applications of satellite remote sensing and marine Geographic Information Systems (GIS) procedures to the practice of sustainable aquaculture in southern Hokkaido, Japan, focusing mainly on kelp and scallop aquaculture. We also developed a suitable aquaculture site-selection model (SASSM) for suspension culture of Gagome (a kelp species) in the same region. Models for Japanese kelp and Gagome showed that the distributions of the most suitable areas for both species overlapped. Competition between kelps was especially marked along the coastline between Hakodate and Esan. In addition, we examined the impact of oceanographic environmental changes and atmospheric events on scallop and kelp aquaculture sites, demonstrating that variations in the coastal Oyashio Current and the Tsugaru Warm Current significantly influenced the growth and harvesting seasons of scallops and kelps in Funka Bay and other sections of southern Hokkaido. Because a strong El Niño event occurred in 2010, January of that year was extremely cold. The proportion of suitable areas for both scallops and kelps during their respective growing seasons contracted in 2010. Thus, shifts in oceanographic and atmospheric conditions should be incorporated into sustainability management planning for coastal scallop and kelp aquaculture in southern Hokkaido.
  • Shengqiang Wang, Joji Ishizaka, Toru Hirawake, Yuji Watanabe, Yuanli Zhu, Masataka Hayashi, Sinjae Yoo
    Optics Express 23 (8) 10301 - 10318 1094-4087 2015年01月 [査読有り][通常論文]
     
    © 2015 Optical Society of America.Phytoplankton size structure plays an important role in ocean biogeochemical processes. The light absorption spectra of phytoplankton provide a great potential for retrieving phytoplankton size structure because of the strong dependence on the packaging effect caused by phytoplankton cell size and on different pigment compositions related to phytoplankton taxonomy. In this study, we investigated the variability in light absorption spectra of phytoplankton in relation to the size structure. Based on this, a new approach was proposed for estimating phytoplankton size fractions. Our approach use the spectral shape of the normalized phytoplankton absorption coefficient (aph(λ)) through principal component analysis (PCA). Values of aph(λ) were normalized to remove biomass effects, and PCA was conducted to separate the spectral variance of normalized aph(λ) into uncorrelated principal components (PCs). Spectral variations captured by the first four PC modes were used to build relationships with phytoplankton size fractions. The results showed that PCA had powerful ability to capture spectral variations in normalized aph(λ), which were significantly related to phytoplankton size fractions. For both hyperspectral aph(λ) and multiband aph(λ), our approach is applicable. We evaluated our approach using wide in situ data collected from coastal waters and the global ocean, and the results demonstrated a good and robust performance in estimating phytoplankton size fractions in various regions. The model performance was further evaluated by aph(λ) derived from in situ remote sensing reflectance (Rrs(λ)) with a quasi-analytical algorithm. UsingRrs(λ) only at six bands, accurate estimations of phytoplankton size fractions were obtained, with R2 values of 0.85, 0.61, and 0.76, and root mean-square errors of 0.130, 0.126, and 0.112 for micro-, nano-, and picophytoplankton, respectively. Our approach provides practical basis for remote estimation of phytoplankton size structure using aph(λ) derived from satellite observations or rapid field instrument measurements in the future.
  • 堀 雅裕, 村上 浩, 宮崎 理紗, 本多 嘉明, 梶原 康司, 奈佐原 顕郎, 中島 孝, 入江 仁士, 虎谷 充浩, 平譯 享, 青木 輝夫
    大会講演予講集 大会講演予講集 107 2015年04月 [査読無し][通常論文]
  • Shintaro Takao, Shintaro Takao, Toru Hirawake, Gen Hashida, Hiroshi Sasaki, Hiroshi Hattori, Koji Suzuki, Koji Suzuki, Koji Suzuki
    Polar Biology 37 (11) 1563 - 1578 07224060 2014年07月 [査読有り][通常論文]
     
    Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. However, the relationship between phytoplankton community composition and primary productivity remains elusive in this region. We investigated the community composition and photosynthetic physiology of surface phytoplankton assemblages in the Australian sector of the Southern Ocean from December 2010 to January 2011. There were significant latitudinal variations in hydrographic and biological parameters along 110°E and 140°E. Surface (5 m) chlorophyll a (chl a) concentrations measured with high-performance liquid chromatography varied between 0.18 and 0.99 mg m-3. The diatom contribution to the surface chl a biomass increased in the south, as estimated with algal chemotaxonomic pigment markers, while the contributions of haptophytes and chlorophytes decreased. In our photosynthesis-irradiance (P-E) curve experiment, the maximum photosynthetic rate normalized to chl a ((Formula presented.)), initial slope (α*), the maximum quantum yield of carbon fixation (Φc max), and the photoinhibition index (β*) were higher in the region where diatoms contributed >50 % to the chl a biomass. In addition, there were statistically significant correlations between the diatom contribution to the chl a biomass and the P-E parameters. These results suggested that the changes in the phytoplankton community composition, primarily in diatoms, could strongly affect photosynthetic physiology in the Australian sector of the Southern Ocean. © 2014 Springer-Verlag Berlin Heidelberg.
  • Kohei Matsuno, Atsushi Yamaguchi, Toru Hirawake, Shigeto Nishino, Jun Inoue, Takashi Kikuchi
    Polar Biology 38 1075 - 1079 07224060 2015年02月 [査読無し][通常論文]
     
    © 2015, Springer-Verlag Berlin Heidelberg.The species composition of Arctic zooplankton differs greatly from that of the zooplankton of the North Pacific and Bering Sea. Particularly with greater warming from sea-ice retreat, the reproduction of North Pacific species transported into the Chukchi Sea and beyond may lead to changes in the Arctic pelagic ecosystem. We report the egg production and hatching of the Pacific copepod Neocalanus flemingeri in the Chukchi Sea based on shipboard experiments performed in September 2013. The reproductive capability of N. flemingeri observed in the Chukchi Sea resembled that reported in the Pacific, with the exception of a lower hatching success. Only 7.5 % of N. flemingeri eggs hatched compared with 93 % in Pacific experiments. Low hatching success is considered to be caused by failures of fertilization. The potential recruitment number for N. flemingeri suggests that it is unlikely to establish expatriate Arctic populations in the near future.
  • Yang Liu, Sei Ichi Saitoh, I. Nyoman Radiarta, Hiromichi Igarashi, Toru Hirawake
    Aquaculture 422-423 172 - 183 00448486 2014年02月 [査読有り][通常論文]
     
    The Japanese scallop (Mizuhopecten yessoensis) is an important commercial species in the Dalian coastal area. The present study employed a suitable aquaculture site-selection model (SASSM) and used satellite remote-sensing data to analyze the spatiotemporal distribution of suitable areas for Japanese scallop aquaculture in the Dalian coastal area from 2003 to 2012. The study area was divided into four marine zones. The results demonstrated that the suitability scores of scallop aquaculture areas were high in May and low in February. The Changhai County (Zone II) and Lushunkou areas (Zone III) exhibited high potential for Japanese scallop aquaculture development. The results of the suitability models were consistent with the existing scallop aquaculture in the study area. These zones, combined with climatic events [the winter East Asian Monsoon (EAM) and El Niño/La Niña-Southern Oscillation (ENSO) events], were used to examine the impact of climate variability on scallop aquaculture. Results suggest that the suitability scores in Zone III were more sensitive to changes in environmental factors (e.g., sea surface temperature, chlorophyll-a, and suspended sediment) and climate changes, whereas the correlations among these factors were not significant in Zone II. Adaptation to these changes should be considered when developing plans and management strategies for scallop aquaculture. © 2013 Elsevier B.V.
  • Yang Liu, Sei Ichi Saitoh, I. Nyoman Radiarta, Tomonori Isada, Toru Hirawake, Hiroyuki Mizuta, Hajime Yasui
    ICES Journal of Marine Science 70 (7) 1460 - 1470 10543139 2013年11月 [査読有り][通常論文]
     
    Japanese kelp (Saccharina japonica) is one of the most valuable cultured and harvested kelp species in Japan. In this study, we added a physical parameter, sea surface nitrate (SSN) estimated from satellite remote sensing data, to develop a suitable aquaculture site-selection model (SASSM) for hanging cultures of Japanese kelp in southern Hokkaido, Japan. The local algorithm to estimate SSN was developed using satellite measurements of sea surface temperature and chlorophyll-a. We found a high correlation between satellite- and ship-measured data (r2 = 0.87, RMSE = 1.39). Multi-criteria evaluation was adapted to the SASSM to rank sites on a scale of 1 (least suitable) to 8 (most suitable). We found that 64.4% of the areas were suitable (score above 7). Minamikayabe was identified as the most suitable area, and Funka Bay also contained potential aquaculture sites. In addition, we examined the impact of El Niño/La Niña-Southern Oscillation (ENSO) events on Japanese kelp aquaculture and site suitability from 2003-2010. During El Niño events, the number of suitable areas (scores 7 and 8) decreased significantly, indicating that climatic conditions should be considered for future development of marine aquaculture. © 2013 International Council for the Exploration of the Sea.
  • Shigeto Nishino, Yusuke Kawaguchi, Yusuke Kawaguchi, Jun Inoue, Jun Inoue, Toru Hirawake, Amane Fujiwara, Amane Fujiwara, Ryosuke Futsuki, Jonaotaro Onodera, Michio Aoyama, Michio Aoyama
    Journal of Geophysical Research C: Oceans 21699275 2015年01月 [査読無し][通常論文]
     
    © 2015. American Geophysical Union. A fixed-point observation station was set up in the northern Chukchi Sea during autumn 2013, and for about 2 weeks conductivity-temperature-depth (CTD)/water samplings (6 h) and microstructure turbulence measurements (2 to 3 times a day) were performed. This enabled us to estimate vertical nutrient fluxes and the impact of different types of turbulent mixing on biological activity. There have been no such fixed-point observations in this region, where incoming low-salinity water from the Pacific Ocean, river water, and sea-ice meltwater promote a strong pycnocline (halocline) that stabilizes the water column. Previous studies have suggested that because of the strong pycnocline, wind-induced ocean mixing could not change the stratification to impact biological activity. However, the present study indicates that a combined effect of an uplifted pycnocline accompanied by wind-induced inertial motion and turbulent mixing caused by intense gale-force winds (>10 m s-1) did result in increases in upward nutrient fluxes, primary productivity, and phytoplankton biomass, particularly large phytoplankton such as diatoms. Convective mixing associated with internal waves around the pycnocline also increased the upward nutrient fluxes and might have an impact on biological activity there. For diatom production at the fixed-point observation station, it was essential that silicate was supplied from a subsurface silicate maximum, a new feature that we identified during autumn in the northern Chukchi Sea. Water mass distributions obtained from wide-area observations suggest that the subsurface silicate maximum water was possibly derived from the ventilated halocline in the Canada Basin.
  • Mega L. Syamsuddin, Mega L. Syamsuddin, Sei Ichi Saitoh, Toru Hirawake, Bachri Samsul, Agung B. Harto
    Fishery Bulletin 111 (2) 175 - 188 00900656 2013年04月 [査読有り][通常論文]
     
    The effects of El Niño-Southern Oscillation events on catches of Bigeye Tuna (Thunnus obesus) in the eastern Indian Ocean (EIO) off Java were evaluated through the use of remotely sensed environmental data (sea-surface-height anomaly [SSHA], sea-surface temperature [SST], and chlorophyll-a concentration), and Bigeye Tuna catch data. Analyses were conducted for the period of 1997-2000, which included the 1997-98 El Niño and 1999-2000 La Niña events. The empirical orthogonal function (EOF) was applied to examine oceanographic parameters quantitatively. The relationship of those parameters to variations in catch distribution of Bigeye Tuna was explored with a generalized additive model (GAM). The mean hook rate was 0.67 during El Niño and 0.44 during La Niña, and catches were high where SSHA ranged from-21 to 5 cm, SST ranged from 24°C to 27.5°C, and chlorophyll-a concentrations ranged from 0.04 to 0.16 mg m-3. The EOF analysis confirmed that the 1997-98 El Niño affected oceanographic conditions in the EIO off Java. The GAM results indicated that SST was better than the other environmental factors (SSHA and chlorophyll-a concentration) as an oceanographic predictor of Bigeye Tuna catches in the region. According to the GAM predictions, the highest probabilities (70-80%) for Bigeye Tuna catch in 1997-2000 occurred during oceanographic conditions during the 1997-98 El Niño event.
  • Christopher Mulanda Aura, Christopher Mulanda Aura, Sei Ichi Saitoh, Yang Liu, Toru Hirawake, Katsuhisa Baba, Tooru Yoshida
    Aquaculture Research 47 (7) 2164 - 2182 1355557X 2014年01月 [査読有り][通常論文]
     
    © 2014 John Wiley & Sons Ltd. The determination of the causes for the changes in marine environment in areas with similar oceanic climate forcing on most suitable sites for scallop aquaculture can help to ensure long-term sustainability of the coastal ecosystem. This study assessed aquaculture suitability sites using dominant indicators of marine ecological dynamics on Japanese scallop culture in Funka and Mutsu Bays, Japan as comparative examples. Data sources comprised of Moderate Resolution Imaging Spectroradiometer (MODIS), four dimensional-variational (4D-VAR) data assimilation system, Advanced Land Observing Satellite (ALOS), in situ and buoy measurements. The suitable sites were ranked on a scale of 1 (least suitable) to 8 (most suitable). In the most suitable sites in aquaculture operational areas, Funka Bay had a high proportion (51.1%) than Mutsu Bay (13.7%) for the best performed model. Peaks of aquaculture suitability scores were attributed to potential effects of currents. Extreme sea temperatures (>24°C) in summer 2010 were associated with low performance of the 2010 model in Mutsu Bay and mortality of scallops based on sea temperature-depth visualizations. Future global warming effects are likely to decrease the most suitable culture sites in Funka Bay and loss of similar areas in Mutsu Bay. Thus, change in marine environment influences scallop culture development. Such concepts could form scientific basis for aquaculture planning on designated system of larval distribution and stock management of cultured species to minimize mortality and economic losses.
  • Yang Liu, Sei Ichi Saitoh, Hiromichi Igarashi, Toru Hirawake
    International Journal of Remote Sensing 35 (11-12) 4422 - 4440 01431161 2014年01月 [査読有り][通常論文]
     
    Climate changes affect coastal environments and aquaculture, threatening food security and economic growth. Japanese scallop (Mizuhopecten yessoensis) culture is economically important for the coastal communities of Dalian, China, and Funka Bay, Japan. In this study, we combined satellite remote-sensing data, in situ observations, and a suitable aquaculture site selection model to explore the interactions between marine environments and climate variability over a recent 10-year period (2003-2012). Our selection of appropriate zones in these two Far Eastern regions and our analyses of climatic event (Arctic Oscillation (AO), winter East Asian monsoon (EAM), and El Niño/La Niña Southern Oscillation (ENSO)) and meteorological (precipitation, temperature, and wind) data allowed us to determine the impacts of climate change on regional coastal environments and prospects for scallop aquaculture. These analyses showed that AO and EAM strongly influenced the aquaculture areas on the Dalian coast through their effects on temperature during winter. We also determined that wind was the main driving force behind regional environmental changes during spring. Conversely, ocean conditions and suitable areas in Funka Bay changed rapidly relative to oceanic and atmospheric circulation. In Funka Bay, areas appropriate for scallop aquaculture and variations in chlorophyll-a concentration (which reflect the availability of algal food for scallops) were strongly correlated with ENSO, precipitation, and air temperature. These correlations demonstrate the influence of oceanic and atmospheric parameters on the productivity of scallop aquaculture in Funka Bay. Adaptation to oceanic and atmospheric changes should be considered when developing plans and management strategies for coastal scallop aquaculture in northeast Asia. © 2014 © 2014 Taylor & Francis.
  • A. Fujiwara, A. Fujiwara, T. Hirawake, K. Suzuki, I. Imai, S. I. Saitoh
    Biogeosciences 11 1705 - 1716 17264170 2014年04月 [査読無し][通常論文]
     
    This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. Distribution patterns of phytoplankton groups in the late summers of 2008-2010 were analysed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years-the sea ice retreat in 2008 was 1-2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure. © 2014 Author(s).
  • Shintaro Takao, Shintaro Takao, Toru Hirawake, Gen Hashida, Hiroshi Sasaki, Hiroshi Hattori, Koji Suzuki, Koji Suzuki, Koji Suzuki
    Polar Biology 37 1563 - 1578 07224060 2014年01月 [査読無し][通常論文]
     
    © 2014, Springer-Verlag Berlin Heidelberg.Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. However, the relationship between phytoplankton community composition and primary productivity remains elusive in this region. We investigated the community composition and photosynthetic physiology of surface phytoplankton assemblages in the Australian sector of the Southern Ocean from December 2010 to January 2011. There were significant latitudinal variations in hydrographic and biological parameters along 110°E and 140°E. Surface (5 m) chlorophyll a (chl a) concentrations measured with high-performance liquid chromatography varied between 0.18 and 0.99 mg m−3. The diatom contribution to the surface chl a biomass increased in the south, as estimated with algal chemotaxonomic pigment markers, while the contributions of haptophytes and chlorophytes decreased. In our photosynthesis–irradiance (P–E) curve experiment, the maximum photosynthetic rate normalized to chl a ((Formula presented.)), the maximum quantum yield of carbon fixation (Φc max), and the photoinhibition index (β*) were higher in the region where diatoms contributed >50 % to the chl a biomass. In addition, there were statistically significant correlations between the diatom contribution to the chl a biomass and the P–E parameters. These results suggested that the changes in the phytoplankton community composition, primarily in diatoms, could strongly affect photosynthetic physiology in the Australian sector of the Southern Ocean.
  • SAITOH Sei−Ichi, MUGO Robinson, RADIARTA I Nyoman, ASAGA Shinsuke, TAKAHASHI Fumihiro, HIRAWAKE Toru, ISHIKAWA Yoichi, AWAJI Toshiyuki, IN Teiji, SHIMA Shigeki
    ICES Journal of Marine Science 68 (4) 687 - 695 1054-3139 2011年03月 [査読有り][通常論文]
  • Matsuno Kohei, Yamaguchi Atsushi, Hirawake Toru, Imai Ichiro
    Polar Biology 34 (9) 1349 - 1360 0722-4060 2011年09月 [査読有り][通常論文]
  • Atsushi Yamaguchi, Tomoe Homma, Rui Saito, Kohei Matsuno, Hiromichi Ueno, Toru Hirawake, Ichiro Imai
    Plankton and Benthos Research 8 116 - 123 18808247 2014年01月 [査読無し][通常論文]
     
    © The Plankton Society of Japan.Stratified zooplankton sampling was conducted in the subarctic Pacific in June 2009 at four stations along 47°N from 0 to 3,000 m depth to evaluate longitudinal changes in population structure and vertical distribution of the dominant copepod species. At the westernmost station (160°E), the population structure of Eucalanus bungii and Metridia pacifica was dominated by early copepodid stages. In E. bungii, nauplii were abundant and adult females had developed ovaries at 160°E, while at the three stations to the east (167°E, 174°E and 179°W), no E. bungii nauplii were collected, and the resting stages were dominant. This suggests the species was reproducing near 160°E and in diapause in the east. In all three Neocalanus species analyzed (N. cristatus, N. flemingeri and N. plumchrus), late copepodid stages were dominant at the eastern three stations. Lipid accumulation in the fifth copepodid stage of Neocalanus spp. was greater in the west than in the east. This probably resulted from better food conditions and lower temperatures in the west, where copepods could consume more food during development than in the east.
  • Hirawake Toru, Takao Shintaro, Horimoto Naho, Ishimaru Takashi, Yamaguchi Yukuya, Fukuchi Mitsuo
    Polar Biology 34 (2) 291 - 302 0722-4060 2011年02月 [査読有り][通常論文]
  • Kenshi Kuma, Ryohei Sasayama, Nanako Hioki, Yuichiroh Morita, Yutaka Isoda, Tohru Hirawake, Keiri Imai, Takafumi Aramaki, Tomohiro Nakamura, Jun Nishioka, Naoto Ebuchi
    Journal of Oceanography 70 377 - 387 09168370 2014年01月 [査読無し][通常論文]
     
    In the southwestern Okhotsk Sea, the cold water belt (CWB) is frequently observed on satellite images offshore of the Soya Warm Current flowing along the northeastern coast of Hokkaido, Japan, during summertime. It has been speculated that the CWB is upwelling cold water that originates from either subsurface water of the Japan Sea off Sakhalin or bottom water of the Okhotsk Sea. Hydrographic and chemical observations (nutrients, humic-type fluorescence intensity, and iron) were conducted in the northern Japan Sea and southwestern Okhotsk Sea in early summer 2011 to clarify the origin of the CWB. Temperature-salinity relationships, vertical distributions of chemical components, profiles of chemical components against density, and the (NO3 + NO2)/PO4 relationship confirm that water in the CWB predominantly originates from Japan Sea subsurface water. © 2014 The Oceanographic Society of Japan and Springer Japan.
  • Hirawake Toru, Shinmyo Katsuhito, Fujiwara Amane, Saitoh Sei-ichi
    ICES Journal of Marine Science 69 (7) 1194 - 1204 1054-3139 2012年09月 [査読有り][通常論文]
     研究論文(学術雑誌)
  • NISHINO Shigeto, KIKUCHI Takashi, YAMAMOTO‐KAWAI Michiyo, KAWAGUCHI Yusuke, HIRAWAKE Toru, ITOH Motoyo
    Journal of Oceanography 67 (3) 305 - 314 0916-8370 2011年06月 [査読有り][通常論文]
  • 平田 貴文, 平譯 享, 境田 太樹, 山口 寿史, 鈴木 光次, 石坂 丞二, 小林 拓, 村上 浩, 虎谷 充浩, 藤原 周, 齊藤 誠一
    日本リモートセンシング学会誌 日本リモートセンシング学会誌 34 (4) 278 - 285 0289-7911 2014年 [査読無し][通常論文]
     
    Several ocean algorithms have been developed for the Second-Generation Global Imager (SGLI) on the Global Climate Observation Mission - Climate (GCOM-C) satellite (planned launch, 2016). Here we present verification of the ocean algorithms designed to retrieve the inherent optical properties, phytoplankton functional types and primary productivity. The satellite algorithm verification is defined here to evaluate accuracy of target variables using input parameter(s) obtained from in situ measurements rather than from satellite measurements. The verification of inherent optical properties (IOP) algorithms showed RMSE of 0.12, 0.22, and 0.05 for the absorption coefficient of phytoplankton, detrital materials plus colored dissolved organic materials, and the backscattering coefficient of suspended particles, respectively. Verification of the primary production algorithm indicated that it almost satisfied the values measured in situ by a factor of 2. Other algorithms such as phytoplankton functional types (PFTs) and size classes (PSCs) algorithms, which can be derived from the optical properties of phytoplankton rather than from chlorophyll a concentration, showed RMSE of 10.1-11.6 % in a relative abundance of PFTs/PSCs. Towards validation of the ocean algorithms, a radiometer called the Compact-Optical Profiling System (C-OPS), as well as another compact radiometer system specifically designed for turbid waters, were configured for in situ observation. The latter was found to reduce shelf-shading error to within 10 %. Furthermore, Ultra-High Performance Liquid Chromatography systems (UHPLC) have been developed for rapid measurements (7 min) of phytoplankton pigments in a water sample (conventional HPLC takes 30 min). This new system significantly increases spatio-temporal coverage of in situ data required for algorithm validation.
  • OKAMOTO S., HIRAWAKE T., SAITOH S.‐I.
    Deep Sea Research II 57 (17-18) 1608 - 1617 0967-0645 2010年09月 [査読有り][通常論文]
  • KOUBBI Philippe, KOUBBI Philippe, OZOUF−COSTAZ Catherine, GOARANT Anne, GOARANT Anne, MOTEKI Masato, HULLEY Percy−alexander, CAUSSE Romain, DETTAI Agnes, DUHAMEL Guy, PRUVOST Patrice, TAVERNIER Eric, POST Alexandra L., BEAMAN Robin J., RINTOUL Stephen R., HIRAWAKE Toru, HIRANO Daisuke, ISHIMARU Takashi, RIDDLE Martin, HOSIE Graham
    Polar Science 4 (2) 115 - 133 1873-9652 2010年08月 [査読有り][通常論文]
  • HASHIHAMA Fuminori, HASHIHAMA Fuminori, UMEDA Haruko, UMEDA Haruko, HAMADA Chiaki, KUDOH Sakae, KUDOH Sakae, HIRAWAKE Toru, SATOH Kazuhiko, FUKUCHI Mitsuo, FUKUCHI Mitsuo, KASHINO Yasuhiro
    Marine Biology 157 (10) 2263 - 2278 0025-3162 2010年10月 [査読有り][通常論文]
  • S. Takao, T. Hirawake, S. W. Wright, S. W. Wright, K. Suzuki, K. Suzuki, K. Suzuki
    Biogeosciences 9 3875 - 3890 17264170 2012年10月 [査読無し][通常論文]
     
    Phytoplankton population dynamics play an important role in biogeochemical cycles in the Southern Ocean during austral summer. Recent environmental changes such as a rise in sea surface temperature (SST) are likely to impact on net primary productivity (NPP) and phytoplankton community composition. However, their spatiotemporal relationships are still unclear in the Southern Ocean. Here we assessed the relationships between NPP, dominant phytoplankton groups, and SST in the Indian sector of the Southern Ocean over the past decade (1997-2007) using satellite remote sensing data. As a result, we found a statistically significant reduction in NPP in the polar frontal zone over the past decade during austral summer. Moreover, the decrease in NPP positively correlated with the dominance of diatoms (Kendall's rank correlation τ= 0.60) estimated by a phytoplankton community composition model, but not correlated with SST. In the seasonal ice zone, NPP correlated with not only the dominance of diatoms positively (τ= 0.56), but also the dominance of haptophytes (τ=-'0.54) and SST (τ=-'0.54) negatively. Our results suggested that summer NPP values were strongly affected by the phytoplankton community composition in the Indian sector of the Southern Ocean. ©2012 Author(s).
  • Shigeru Aoki, Daisuke Fukai, Toru Hirawake, Shuki Ushio, Stephen R. Rintoul, Hiroshi Hasumoto, Takashi Ishimaru, Hideharu Sasaki, Takashi Kagimoto, Yoshikazu Sasai, Humio Mitsudera
    Journal of Geophysical Research: Oceans 112 (C5) C05019, doi:10.1029/2006JC003712  0148-0227 2007年05月 [査読有り][通常論文]
     
    The spatial and temporal characteristics of cyclonic eddies in the Antarctic Divergence off Adélie Coast are described using repeated in situ observations between 2001 and 2003, satellite observations, and results of a high-resolution ocean general circulation model. Satellite ocean color images and altimetry clearly revealed a series of cyclonic eddies, with diameters of about 100-150 km that were separated by about 150 km in the zonal direction. The eddies are found at almost the same locations and can be traced for at least two months in the spring-summer period. Cold and fresh anomalies were found throughout the water column in the cores of the cyclonic eddies. The water properties in the core of the eddies are similar to water found over the continental slope, 150-200 km to the south. The geopotential anomaly of the cold features was smaller than the sea level anomaly detected with satellite altimetry, indicating that significant barotropic flow is associated with the eddies. The Ocean general circulation model for the Earth Simulator (OFES) reproduces a series of cyclonic eddies similar to those observed, including a significant barotropic component. In the model, the series of eddies appear to originate further west over the continental slope region with no consistent phase propagation. The combination of repeat in situ observations, remote sensing and high-resolution model results confirms the existence of persistent cyclonic eddies near 140°E and suggests the eddies play an important role in the exchange of water across the Antarctic Divergence. Copyright 2007 by the American Geophysical Union.
  • 小林 拓, 平譯 享, 矢吹 正教, 上田 沙也子, 長田 和雄, 塩原 匡貴, 福地 光男, コバヤシ ヒロシ, ヒラワケ トオル, ヤブキ マサタカ, ウエダ サヤコ, オサダ カズオ, シオバラ マサタカ, フクチ ミツオ, Hiroshi Kobayashi, Toru Hirawake, Masanori Yabuki, Sayako Ueda, Kazuo Osada, Masataka Shiobara, Mitsuo Fukuchi
    南極資料 南極資料 54 (0) 465 - 473 2010年12月 [査読無し][通常論文]
     
    東京海洋大学「海鷹丸」の南極海研究航海において,大気エアロゾルの光学的厚さ(AOT)の観測を実施した.南極海インド洋セクターでの500 nmでのAOTは,0.02-0.12の範囲であった.南極大陸沿岸域でのAOTは比較的低く,0.02前後であった.40-60゜Sの海域では,0.1以上の値を示すことがあった.インド洋低中緯度帯でのAOTは,0.05-0.15の範囲であった.風速とAOTとに正の相関がみられたことから,南極海では光学的に海塩粒子が卓越し,風速がAOTに影響を及ぼしていると考えられる.AOTが高くなるにつれ,オングストローム指数は減少した.AOTの波長スペクトルにおいて,380 nmと870 nmのAOTはべき関数からずれる傾向がみられた.レイリーの光学的厚さの算出方法を比較したところ,ずれが大幅に改善される可能性が示された.今後,より観測精度を高めていくためには,機器定数の精度を把握するとともに,レイリーの光学的厚さの算出方法の見直しなどが必要である.Aerosol optical thickness (AOT) was measured during Antarctic research cruises of R V Umitaka-Maru. The measured AOTs at 500 nm in the Indian sector of the Antarctic Ocean ranged from 0.02 to 0.12. In Antarctic coastal waters, the AOTs were as low as around 0.05. On the other hand, the some AOTs were higher than 0.1 from 40゜S to 60゜S. In middle and low latitude regions of the Indian Ocean, the AOTs ranged from 0.05 to 0.15. The AOTs were correlated with wind speed. It is indicated that sea-salt particles, generated by wind, dominated optically and wind speed affected the AOT in the Antarctic Ocean. Angstro¨m exponent decreased with increasing AOT. In the AOT wavelength spectra, some AOTs in 380 nm and 870 nm tended to deviate from the power function. Comparing calculation methods of Rayleigh optical thickness suggested a possibility of reducing the deviations of these AOTs. In the future, accuracy check of the instrument constant and review of the calculation method of Rayleigh optical thickness are recommended to enhance the accuracy of maritime AOT measurement.
  • Lihan Tukimat, Saitoh Sei-Ichi, Iida Takahiro, Hirawake Toru, Iida Kohji
    Estuarine, Coastal and Shelf Science in press (2) in press - 249 0272-7714 2008年06月 [査読有り][通常論文]
  • HASHIHAMA Fuminori, HIRAWAKE Toru, KUDOH Sakae, KANDA Jota, FURUYA Ken, YAMAGUCHI Yukuya, ISHIMARU Takashi
    Polar Science 2 (2) 109 - 120 1873-9652 2008年 [査読無し][通常論文]
  • Polar Biology 31 1011 - 1015 2008年 [査読無し][通常論文]
  • Susanne Preunkert, Michel Legrand, Bruno Jourdin, Bruno Jourdin, Cyril Moulin, Sauveur Belviso, Nobue Kasamatsu, Mitsuo Fukuchi, Toru Hirawake, Toru Hirawake
    Journal of Geophysical Research Atmospheres 112 (D6) D06306, doi:10.1029/2006JD007585  01480227 2007年03月 [査読有り][通常論文]
     
    A multiple year-round study of atmospheric dimethyl sulfide (DMS) (from December 1998 to April 2003) as well as sulfur-derived aerosols (methanesulfonic acid (MSA) and non-sea-salt sulfate) (from March 1991 to February 2003) was conducted at Dumont d'Urville, coastal Antarctica. The three sulfur-derived species exhibit a seasonal cycle characterized by maxima in midsummer (January). Whereas the interannual variability of winter levels remains low, a strong interannual variability is shown in summer, particularly for DMS and MSA, and to a lesser extent for non-sea-salt sulfate. Over the 1998-2003 time period, January 2002 stands out with high values for all sulfur species. These interannual variabilities of atmospheric summer levels are examined in the light of seawater chlorophyll a content derived from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data (themselves compared to field measurements made south of 60°S), oceanic DMS levels estimated from chlorophyll a SeaWiFS data, and various sea-ice indices. Copyright 2007 by the American Geophysical Union.
  • Unusual abundance of appendicularians in the seasonal ice zone (140°E) of the Southern Ocean
    Polar Bioscience 19 133 - 141 2006年 [査読無し][通常論文]
  • Distribution of Copepoda along 140°E in the Indian sector of the Southern Ocean
    Polar Bioscience 20 140 - 146 2006年 [査読無し][通常論文]
  • Toru Hirawake, Tsuneo Odate, Mitsuo Fukuchi
    Geophysical Research Letters 32 1 - 4 00948276 2005年03月 [査読無し][通常論文]
     
    The variation in the phytoplankton biomass over a decadal time scale, and its relationship with the Antarctic Circumpolar Wave (ACW) and climate change, has been poorly interpreted because of the limited satellite chlorophyll a (chl a) data compared with the physical parameters from satellite. We analyzed a long-term chl a data set along the Japanese Antarctic Research Expedition (JARE) cruise tracks since 1965 to investigate inter-annual variation of phytoplankton biomass. In the Southern Ocean, increasing trends of chl a and the spreading of higher chl a area to the north with 3-7 year cycles were found. Although relationships between the decadal change in chl a and climate change such as variation of sea ice extent and the El Niño are still obscure, large variation of primary production in proportion to the chl a is implied. Copyright 2005 by the American Geophysical Union.
  • Yoriko Arai, Yoriko Arai, Toru Hirawake, Toru Hirawake, Tsuneo Odate, Tsuneo Odate, Kentaro Watanabe, Kentaro Watanabe, Mitsuo Fukuchi, Mitsuo Fukuchi
    Polar Bioscience 16 - 27 13446231 2005年01月 [査読無し][通常論文]
     
    We investigated the distribution of chlorophyll-a (Chl-a) and sea surface temperature (SST) off the sea ice region south of 64°S in East Antarctica between 20°E and 60°E during austral summers, 1998-2002. We used satellite multi-sensor remote sensing datasets including ocean color Chl-a, SST and sea ice concentration. High concentrations of Chl-a (>0.5 mg m-3) were generally observed in colder water below 0°C. Phytoplankton blooms were extended into shallow areas along the isobath. SST distribution exhibited two patterns. In the first pattern, warm water located to the north of this region associated with polynya in early spring. The second pattern was characterized by distribution of cold water throughout the study area. A shift of the Antarctic Circumpolar Current (ACC) is considered to affect this difference between SST distributions. The cold water from the Antarctic coastal current mixed with meltwater was expected to provide vertical stability of the water column for phytoplankton blooms. These results suggest that the phytoplankton blooms in this study area during austral summer can be attributed to water conditions affected by melting sea ice, movement of the ACC and sea floor topography. © 2005 National Institute of Polar Research.
  • A simple method for estimating phytoplankton abundance using a surface seawater monitoring system off Syowa Station during austral summer
    Polar Bioscience 18 28 - 34 2005年 [査読無し][通常論文]
  • Journal of the Marine Biological Association of the United Kingdom 85 283 - 289 2005年 [査読無し][通常論文]
  • HIRAWAKE T, KUDOH S, AOKI S, ODATE T, FUKUCHI M
    International Journal of Remote Sensing 26 (10) 2035 - 2044 0143-1161 2005年 [査読無し][通常論文]
  • Eddies revealed by SeaWiFS ocean color images in the Antarctic Divergence zone near 140°E
    Geophysical Research Letters 30 (9) 1458, doi:10.1029/2003GL016996  2003年 [査読無し][通常論文]
  • 工藤 栄, 伊倉 千絵, 高橋 晃周, 西川 淳, 石川 輝, 鷲山 直樹, 平譯 享, 小達 恒夫, 渡辺 研太郎, 福地 光男, クドウ サカエ, イクラ チエ, タカハシ アキノリ, ニシカワ ジュン, イシカワ アキラ, ワシヤマ ナオキ, ヒラワケ トオル, オダテ ツネオ, ワタナベ ケンタロウ, フクチ ミツオ, Sakae Kudoh, Chie Ikura, Akinori Takahashi, Jun Nishikawa, Akira Ishikawa, Naoki Washiyama, Toru Hirawake, Tsuneo Odate, Kentaro Watanabe, Mitsuo Fukuchi
    南極資料 = Antarctic Record 南極資料 = Antarctic Record 45 (3) 279 - 296 2002年03月 [査読無し][通常論文]
     
    第39次および第40次日本南極地域観測隊夏期行動期間中(それぞれ1997年12月4日∿12月13日及び, 1998年2月15日∿3月19日と1998年12月3日∿12月20日及び1999年2月24日∿3月19日), 南大洋インド洋区で南極観測船「しらせ」の航路に沿って表層海水をポンプ連続揚水し, プランクトンネットで3∿8時間濾過して動物プランクトン試料を得た。動物プランクトンの湿重量測定を行い, 航路に沿って現存量を整理した。連続試料採取したにもかかわらず, 隣接した試料間においても現存量の変動は大きく, 動物プランクトンの不均一分布が伺えた。動物プランクトン現存量は「しらせ」南下時に顕著に認められる海洋前線通過時にしばしばきわだって大きくなり, その前後の海域で得られた値との格差は際立っていた。これら海洋前線では水温・塩分変動が大きく, 南大洋インド洋海区を四つの海域(亜熱帯海域, 亜南極海域, 極前線海域, 南極海域)に区切っている。2回の航海で得た現存量の平均値を比較したところ, 高緯度海域ほど平均値が大きくなる傾向があり, 南極海域で最大となった。南極海域の内でもプリッツ湾沖から東方にかけての海域(東経70-110°)で現存量が大きく, これまでの停船観測結果で推察されていた同海域の生物生産性が高いことに呼応する現象と考えられた。また, リュツォ・ホルム湾沖からアムンゼン湾沖の大陸近くの航行時に得られた現存量は, より沖合部を航行する東経110-150°間に得られた値よりも1/2程小さなものであり, さらに, 東経110°以東において大陸沿岸よりを航行したJARE-39とやや沖合いを航行したJARE-40で得られたデータ間でも前者の現存量が小さく, これらから南極海域では表層水中の動物プランクトン量が生物生産期間がより短くなると考えられる沿岸部ほど小さいことが推察された。今回表層水中で連続試料採取して得られた動物プランクトン湿重量値は, 過去四半世紀間に停船観測において同海域で主にプランクトンネット採集によって得られた値と大きくは異なってはいなかった。動物プランクトン分布の正確な測定のためには動物プランクトンの鉛直分布特性など考慮する必要があるが, 海域ごとの空間分布特性や海域内での変動性などの研究には今回のようなポンプ揚水による試料採集でも適用可能な部分が多く, その研究実施方法の容易さを考慮すると今後の長期的な動物プランクトンモニタリングなどに適した手法と思われた。Wet weight of the net zooplankton biomass (>315μm, collecting NGG54 netting) in the surface water of the Indian Ocean sector of the Southern Ocean was analyzed using continuously pumped-up water from ca. 8m depth during the two cruises of the 39th (4 Dec.-13 Dec. 1997 and 15 Feb.-19 Mar. 1998) and 40th (3 Dec.-20 Dec. 1998 and 24 Feb.-19 Mar. 1999) Japanese Antarctic Research Expeditions (JARE). The biomass varied widely; even samples collected from the same water body (difference of distance among the samples were several-100 miles away) sometimes had differences of 2-3 orders of magnitude. The biomass obtained around ocean frontal regions such as the Sub-tropical Front, Sub-Antarctic Front and Polar Front, an ocean ridge area (Kerguelen plateau) and off Prydz Bay tended to show higher biomass than other areas, often exceeding 500mg/m^3. The mean biomasses among the 4 water bodies separated by the ocean fronts, were 50,68,76 and 137mg/m^3 in the Sub-tropical, Sub-Antarctic, Polar Frontal and Antarctic Zones, respectively. In the Antarctic Zone, the biomass tended to decrease from north toward south, and the west and eastward distribution showed high biomass over a relatively extensive area east of Prydz Bay and slightly high abundance offshore of Amundsen Bay. According to previous JAREs and other studies carried out in the Indian Ocean sector, areas which showed constantly higher zooplankton biomass seem to agree well with areas reported as showing higher phytoplankton production or biomass. In spite of the methodological difference, the present results obtained by continuous sampling during the two cruises were very similar to the previous results of K. Takahashi et al. (Mem. Natl Inst. Polar Res., Spec. Issue, 52,209,1998), which was summarized over 22 years data of NORPAC net sampling, and we were able to confirm the surface biomass and distribution of net zooplankton in the Indian Ocean Sector of the Southern Ocean during austral summer. The method applied in the present study is one good way for long-term monitoring of the surface zooplankton biomass along the JARE cruise track, because the sampling requires non-ship time and gives a good estimation of the biomass.
  • Deep-Sea Research II 49 5049 - 5061 2002年 [査読無し][通常論文]
  • Deep-Sea Research II 49 4947 - 4958 2002年 [査読無し][通常論文]
  • 岸野 元彰, 古谷 研, 田口 哲, 平譯 享, 鈴木 光次, 田中 昭彦
    海の研究 海の研究 10 (6) 537 - 559 09168362 2001年11月 [査読無し][通常論文]
     
    海水の光吸収係数は, 海洋の基礎生産や海色リモートセンシングの研究において重要なパラメータの1つである。今まで, その測定法について多くの提案がなされてきた。本稿は, まず吸収係数の定義を明確に定義し, その海洋学における意義を述べた。引き続き, オパールグラス法, グラスファイバー法, 光音響法, 積分球法の原理を述べると共に問題点を挙げた。また, 採水処理しなくて済む現場法についてその原理と問題点をまとめた。引き続き吸収係数の組成分離法について直接分離法と実測値から求めた半理論的分離法を紹介した。最後に人工衛星によるリモートセンシングによる推定法に言及した。
  • 平譯 享, 鈴木 光次, 岸野 元彰, 古谷 研, 田口 哲, 齋藤 誠一, 才野 敏郎, 松本 和彦, 播本 孝史, 佐々木 宏明, 藤木 徹一, 古原 慎一, 柏 俊行
    海の研究 海の研究 10 (6) 471 - 484 0916-8362 2001年 [査読無し][通常論文]
     
    植物プランクトンの光吸収係数は, 海洋の基礎生産や海色リモートセンシングの研究において必要不可欠なパラメータの一つである。その測定法を標準化するために開いたワークショップの成果として, 植物プランクトンの光吸収係数を測定するためのプロトコルを作成した。過去3回のワークショップにおいて, 吸収係数測定法の一つであるQFT法(Quantitative Filter Technique)を中心に, 分光光度計間の比較, 補正式の検討, 植物色素の抽出法の検討を行った。また, 現場型の水中分光吸光度計の利用についても評価を行った。それらの結果をもとに, ろ過方法, 測定方法, さらにデータ管理に至るまで, 推奨するべき方法を提言した。このプロトコルに従って植物プランクトンの光吸収係数を測定することにより, 研究者間の測定値の相互比較が容易となると考えられる。
  • JARE-39, 40 しらせ航路に沿った夏季南大洋インド洋区における表層水中の動物プランクトン現存量
    南極資料 45 (3) 279 - 296 2001年 [査読無し][通常論文]
  • S. Chiba, S. Chiba, T. Hirawake, S. Ushio, N. Horimoto, R. Satoh, Y. Nakajima, T. Ishimaru, Y. Yamaguchi
    Deep-Sea Research Part II: Topical Studies in Oceanography 47 2589 - 2613 09670645 2000年09月 [査読無し][通常論文]
     
    A biological/oceanographic survey was conducted around the Antarctic Divergence (AD) off Adelie Land, Antarctica by the RTV Umitaka-Maru III of Tokyo University of Fisheries in the 1995/1996 Austral summer. Investigations were included (1) characteristics of oceanic structure, (2) primary production and related upper water mass structure, (3) phytoplankton community structure, (4) zooplankton community structure, (5) distribution of Antarctic krill, and (6) optical properties and development of biooptical algorithms for future use of ocean color remote sensing in monitoring phytoplankton biomass. The existence of dense water on the continental slope suggests that the survey area is one of major sources of the Antarctic Bottom Water. We observed a southward meandering of ACC, which allowed the warmer, saline offshore water to intrude south in the eastern part of the area. This east-west gradient in water mass seemed to influence the formation of the local trophic structure in the research area. In the western area, primary productivity was high, and diatoms and copepods dominated, particularly around the AD. The eastern part, however, showed low primary productivity, with a relative dominance of pico- and nanophytoplankton and high abundance of salps. Antarctic krill was distributed mostly in the south of the AD, and its biomass was low compared to previous records, both from adjacent areas and from other Antarctic regions. A biooptical algorithm obtained from this study did not agree with the conventional global algorithm, suggesting the need for constructing local algorithms appropriate for Antarctic Waters. (C) 2000 Elsevier Science Ltd.
  • Photosynthetic characteristics of phytoplankton off Adelie Land, Antarctica, during the austral summer
    Polar Bioscience 13 28 - 42 2000年 [査読無し][通常論文]
  • ODATE T, HIRAWAKE T, TANIMURA A, FUKUSHI M
    Journal of Oceanography 56 (2) 185 - 196 0916-8370 2000年 [査読無し][通常論文]
  • HIRAWAKE T, SATOH H, ISHIMARU T, YAMAGUCHI Y, KISHINO M
    Journal of Oceanography 56 (3) 245 - 260 0916-8370 2000年 [査読無し][通常論文]
  • Primary production in the ROPME Sea Area
    Offshore Environment of the ROPME Sea Area after the War - related Oil Spill - Results of the 1993-4 Umitaka-Maru cruises 181 - 191 1998年 [査読無し][通常論文]
  • Distribution of turbidity in the ROPME Sea Area
    Offshore Environment of the ROPME Sea Area after the War - related Oil Spill - Results of the 1993-4 Umitaka-Maru cruises 49 - 63 1998年 [査読無し][通常論文]
  • Photosynthetic characteristics and primary productivity of phytoplankton in the Arabian Sea and the Indian Ocean during the NE monsoon season
    La mer 35 (4) 157 - 167 1997年 [査読無し][通常論文]

書籍

  • Bio/Chemiluminescence and its Application to Photosynthesis
    ()
    Research Signpost 2005年

その他活動・業績

教育活動情報

主要な担当授業

  • 海洋計測学入門
    開講年度 : 2017年
    課程区分 : 学士課程
    開講学部 : 水産学部
  • 大学院共通授業科目(教育プログラム):南極学
    開講年度 : 2017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 : 海氷、物理、生物、生態系、ブライン、植物プランクトン、動物プランクトン、サロマ湖、オホーツク海
  • 空間統計学入門
    開講年度 : 2017年
    課程区分 : 学士課程
    開講学部 : 水産学部
  • 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 : 2017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 : 北極、地球観測
  • 衛星海洋学
    開講年度 : 2017年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 地球観測衛星、リモートセンシング、海洋環境、海洋光学、クロロフィルa濃度、基礎生産、海面水温、海面高度、海上風、海面塩分、海氷
  • 海洋計測学
    開講年度 : 2017年
    課程区分 : 学士課程
    開講学部 : 水産学部
    キーワード : 電磁波,測位,電波測位,衛星測位,衛星リモートセンシング,CTD,音波,測深,音響測深,魚群探知機,ソナー,ドップラー流向流速計


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