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Last Updated :2024/10/21

Researcher Profile and Settings

Master

Affiliation (Master)

  • Faculty of Fisheries Sciences　Marine Bioresource and Environmental Science　Marine Biology and Biodiversity

Affiliation (Master)

  • Faculty of Fisheries Sciences　Marine Bioresource and Environmental Science　Marine Biology and Biodiversity

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Profile and Settings

Degree

  • Ph. D.（2013/03 Hokkaido University）

Profile and Settings

  • Name (Japanese)

    Kohei

  • Name (Kana)

    Matsuno

  • Name

    201401062013009337

Alternate Names

Achievement

Research Interests

  • ZooScan   diatoms   マイクロプランクトン   気候変動   グリーンランド   Antarctic Ocean   Optical plankton counter   size spectra   Sediment trap   community structure   phytoplankton   Copepoda   Arctic Ocean   Zooplankton   

Research Areas

  • Life sciences / Aquaculture
  • Environmental science/Agricultural science / Environmental dynamics

Research Experience

  • 2017/10 - Today Hokkaido University Faculty of Fisheries Sciences, Division of Marine Bioresource and Environmental Science
  • 2019/02 - 2019/06 University of Tasmania Antarctic Climate and Ecosystems (ACE) CRC Adjunct Professor
  • 2016/04 - 2017/09 Australia Antarctic Division JSPS Postdoctoral Fellow for Research Abroad
  • 2013/04 - 2016/03 National Institute of Polar Research Arctic Environment Research Center Project researcher

Education

  • 2008/04 - 2013/03  Hokkaido University  Graduate School of Fisheries Sciences  Marine Bioresource and Environmental Science
  • 2004/04 - 2008/03  Hokkaido University  School of Fisheries Sciences

Committee Memberships

  • 2021/04 - Today   The Plankton Society of Japan   Council
  • 2020/12 -2023/11   PICES   Working Group 44: Joint PICES/ICES Working Group on Integrated Ecosystem Assessment for the Northern Bering Sea - Chukchi Sea (NBS-CS) Member

Awards

  • 2018/05 The Oceanographic Society of Japan The Okada Prize
     
    受賞者: 松野孝平
  • 2017/03 The Plankton Society of Japan Young Investigators Award of the Plankton Society of Japan
     
    受賞者: Matsuno Kohei
  • 2016/03 National Institute of Polar Research GRENE Arctic Project Young Researcher Award
     
    受賞者: Matsuno Kohei
  • 2013/03 北海道大学大学院水産科学院 伊藤一隆賞
     
    受賞者: 松野孝平
  • 2012/03 2012年度日本海洋学会春季大会 ベストポスター賞
     
    受賞者: 松野孝平

Published Papers

  • Kohei Matsuno, Rikuto Sugioka, Yurika Maeda, Ryan Driscoll, Fokje L. Schaafsma, Sara Driscoll, Atsushi Yamaguchi, Ryuichi Matsukura, Hiroko Sasaki, Hiroto Murase
    Progress in Oceanography 229 103360 - 103360 0079-6611 2024/12 [Refereed][Not invited]
  • Kosuke Egashira, Yu-Sin Huang, Kohei Matsuno, Atsushi Yamaguchi
    Bulletin of Fisheries Sciences, Hokkaido University 74 (1) 23 - 33 2024/08 [Not refereed][Not invited]
  • Li Wang, Xufa Ma, Dongwoo Kim, Kohei Matsuno, Atsushi Yamaguchi
    Bulletin of Fisheries Sciences, Hokkaido University 74 (1) 13 - 22 2024/08 [Not refereed][Not invited]
  • Fokje L. Schaafsma, Kohei Matsuno, Ryan Driscoll, Hiroko Sasaki, Marin van Regteren, Sara Driscoll, Ryuichi Matsukura, Rikuto Sugioka, Ippei Urabe, Hiroto Murase, Jan Andries van Franeker
    Progress in Oceanography 226 103303 - 103303 0079-6611 2024/08 [Refereed][Not invited]
  • Ryota Akino, Daiki Nomura, Reishi Sahashi, Manami Tozawa, Mariko Hatta, Kohei Matsuno, Wakana Endo, Takuhei Shiozaki, Tatsuya Kawakami, Masato Ito, Akihiko Murata, Amane Fujiwara
    Elem Sci Anth 12 (1) 2024/05/27 
    To understand the impact of the melting of late summer Arctic brash ice on the surface waters of the Chukchi Sea, we collected sea-ice samples during 2021. Floating sea ice was collected by a wire mesh pallet cage from the side of the R/V Mirai. We measured physical and biogeochemical parameters such as salinity, oxygen stable isotopic ratios, turbidity, and concentrations of chlorophyll-a and nutrients. The samples of brash ice were multiyear ice based on satellite back-trajectory analysis. Comparison of nutrient concentrations in brash ice with those of seawater samples from the temperature minimum layer similar to the water in the sea ice originated suggested that the characteristics of the brash ice were greatly affected by biogeochemical processes such as remineralization. The extremely high turbidity and concentrations of chlorophyll-a observed in the brown/green ice samples reflected the impact of sediment as well as the influence of biological activities. The N:P ratios were less than 1 because of the high phosphate concentrations, even though the ammonium concentrations were high. We hypothesized that this low N:P ratio reflected the combined effects of the accumulation of nutrients due to remineralization in the biofilm and differences of remineralization rate and adsorption features of nitrogen and phosphorus. Based on the high nitrate and ammonium concentrations in the sea-ice samples, we postulated a marked impact of sea-ice meltwater on the nitrogen cycle in the nitrate-depleted surface waters of the Chukchi Sea during late summer. We estimated that meltwater nitrogen could support 0.3%–2.6% of primary production in the northern Chukchi Sea. Our results suggest that high-turbidity ice will play an important role as a source of nutrients to the ocean during melting of sea ice, and understanding its distribution, amount, and geochemical characteristics is vital.
  • Koki Tokuhiro, Kohei Matsuno, Jonaotaro Onodera, Makoto Sampei, Amane Fujiwara, Naomi Harada, Barbara Niehoff, Eva-Maria Nöthig, Atsushi Yamaguchi
    Journal of Plankton Research 46 (2) 183 - 193 0142-7873 2024/01/22 [Refereed][Not invited]
     
    Abstract Calanus hyperboreus is one of the dominant copepod species in the Arctic zooplankton communities. The impact of climate change varies among regions within the Arctic, implying that C. hyperboreus populations may be differently affected at different locations, but knowledge on seasonal population dynamics in relation to biogeography is scarce. To fill this gap, we counted C. hyperboreus in samples from sediment traps that were moored from 2009 to 2014 in three regions of the Arctic Ocean (eastern Fram Strait, northern Chukchi Sea and MacKenzie Trough). The C. hyperboreus flux increased between April and May in all regions, likely associated with the ascent from overwintering depth to the surface. In the descent period, high fluxes were observed between July and September in the Fram Strait, between September and November in the northern Chukchi Sea, and between August and October in the MacKenzie Trough, suggesting that the timing of descent varied among the regions characterized by differences in light regime, phytoplankton development and water temperature. The copepodite stage composition in the eastern Fram Strait and the MacKenzie Trough varied with season, suggesting successful local reproduction while it was uniform in the northern Chukchi Sea, possibly because the population is fueled by advection.
  • Daiki NOMURA, Ryota AKINO, Matthew CORKILL, Keizo HIRANO, Akihide KASAI, Seiji KATAKURA, Yusuke KAWAGUCHI, Tatsuya KAWAKAMI, Riri KIMURA, Delphine LANNUZEL, Ryosuke MAKABE, Mirai MATSUURA, Kohei MATSUNO, Klaus MEINERS, Keizo NAGASAKI, Yuichi NOSAKA, Nana SAMORI, Shinnosuke SAKAYA, Eun Yae SON, Ryotaro SUGA, Yumi SUNAKAWA, Keigo D. TAKAHASHI, Masaharu TAKAHASHI, Yuka TAKEDA, Takenobu TOYOTA, Manami TOZAWA, Pat WONGPAN, Hiroshi YOSHIDA, Kazuhiro YOSHIDA, Masaki YOSHIMURA
    Bulletin of Glaciological Research 42 19 - 37 1345-3807 2024
  • Kyosei Morimoto, Yusuke Hamao, Tomoyasu Yamazaki, Shoko Tatamisashi, Masahide Wakita, Kohei Matsuno
    Regional Studies in Marine Science 69 103322 - 103322 2352-4855 2024/01 [Refereed][Not invited]
  • Kunito Yamamae, Yasuhide Nakamura, Kohei Matsuno, Atsushi Yamaguchi
    Progress in Oceanography 219 103155 - 103155 0079-6611 2023/12 [Refereed][Not invited]
  • Shino Kumagai, Kohei Matsuno, Atsushi Yamaguchi
    Frontiers in Marine Science 10 2023/11/29 [Refereed][Not invited]
     
    Drastic environmental changes were noted in the northern Bering Sea in 2018. A reduction in sea ice affected several trophic levels within the ecosystem; this resulted in delayed phytoplankton blooms, the northward shifting of fish stocks, and a decrease in the number of seabirds. Changes in the community composition of zooplankton were reported in 2022, but changes in zooplankton interactions and production have not been reported to date. Therefore, this study examined predator-prey interaction, secondary production, and prey availability for fish to understand the effect of early sea ice melt. Zooplankton size data were estimated from the size spectra obtained using ZooScan based on samples collected in 2017 and 2018. A cluster analysis based on biovolume showed that the zooplankton community could be divided into three groups (Y2017N, Y2017S, Y2018). Y2017N, characterized by low abundance, biomass, and production, Y2017S, characterized by high biovolume and production, which contributed with Calanus spp., and Y2018, characterized by low biovolume but high production, contributed with small copepods, and Bivalvia. In 2017, the highest biovolume group was observed south of St. Lawrence Island, and it was dominated by Calanus spp. and Chaetognatha. Normalized size spectra of this group showed the highest secondary production with present predator-prey interactions, suggesting that the area provides high prey availability for fish larvae and juveniles. In contrast, small copepods and bivalve larvae were dominant in this area in 2018, which contain less carbons and energy, suggesting the prevalence of low-nutrient foods in this year in relation to early sea ice melt.
  • Kohei Matsuno, Kohei Sumiya, Manami Tozawa, Daiki Nomura, Hiroko Sasaki, Atsushi Yamaguchi, Hiroto Murase
    Progress in Oceanography 218 103117 - 103117 0079-6611 2023/11 [Refereed]
  • Minami Ishihara, Kohei Matsuno, Koki Tokuhiro, Yasuhiro Ando, Kazutoshi Sato, Atsushi Yamaguchi
    Frontiers in Marine Science 10 2023/09/20 [Refereed]
     
    Calanus glacialis/marshallae is a dominant zooplankton species in the Pacific Arctic Ocean that is widely distributed in shelf areas, and it plays a vital role in connecting primary production to higher trophic levels. Its phenology is well adapted to hydrography, but there is little available information about regional and diel changes in population structure and grazing features. In this study, we investigated C. glacialis/marshallae during autumn 2019 in the Eastern and Northeastern Chukchi and Canadian basins to reveal geographic and diel variations in population structure, body size, grazing activity, and fatty acid composition. The abundance of C. glacialis/marshallae was found to be high on the slopes and low on the shelves. Body size (prosome length) was well described by the Bělehrádek equation combined with in-situ temperature throughout the sampling region. Cluster analyses based on hydrographic parameters were divided into four regions: southern shelf, northern shelf, slope, and basin. The southern shelf was dominated by copepodite stage five (C5) transported from the Bering Sea by Pacific waters. C4 and C5 were dominant on the northern shelf, suggesting that they grew slower than those on the southern shelf, and the populations also exhibited higher concentrations of fatty acids originating from dinoflagellates than those originating from the pan-Arctic Ocean, indicating low productivity in the region. The population on the slope had the highest abundance, C4 was dominant, and large amounts of diatom-derived eicosapentaenoic acid (EPA). These features are attributed to the upwelling of populations and nutrients that support diatom growth. In the basin, the early copepodite stages of composition were distinctly higher than those recorded in previous studies, because larger amounts of organisms flow into the region, resulting in more extended reproduction periods. In the basin, small and large forms of C5 were simultaneously found, and the small form exhibited a diel grazing activity pattern, but the large forms did not. These findings suggest their well adaptation in changing of the Pacific Arctic Ocean.
  • Aiko Tachibana, Yuri Ohkubo, Kohei Matsuno, Keigo D. Takahashi, Ryosuke Makabe, Masato Moteki
    Polar Biology 0722-4060 2023/07/18 [Refereed]
  • Takumi Teraoka, Kanako Amei, Yutaka Fukai, Kohei Matsuno, Hiroji Onishi, Atsushi Ooki, Tetsuya Takatsu, Atsushi Yamaguchi
    Plankton and Benthos Research 17 (4) 369 - 382 1880-8247 2022/11/30 [Refereed][Not invited]
  • Naoya Kanna, Shin Sugiyama, Takuto Ando, Yefan Wang, Yuta Sakuragi, Toya Hazumi, Kohei Matsuno, Atsushi Yamaguchi, Jun Nishioka, Youhei Yamashita
    Global Biogeochemical Cycles 36 (11) 0886-6236 2022/11 [Refereed][Not invited]
  • Yuri Fukai, Kohei Matsuno, Amane Fujiwara, Koji Suzuki
    Frontiers in Marine Science 9 2296-7745 2022/09/15 [Refereed][Not invited]
     
    Diatoms form dense blooms in the Pacific Arctic region from spring to summer, supporting the unique benthic-pelagic coupling ecosystems. Although the Arctic has a severe light-limited season from autumn to winter, diatoms can proliferate in spring when sufficient light becomes available for photosynthesis. One of the crucial strategies for diatoms to survive in unfavorable growing conditions is to form resting stages. Because of enhanced primary and export production in the Pacific Arctic shelves, many viable diatom resting stages can be detected in the surface sediments. However, little is known about the photophysiological response of viable diatom cells, including resting stages, in sediments to light availability. We conducted a laboratory experiment investigating the photophysiological capabilities of the diatom cells containing resting stages using surface sediments from the Chukchi Sea shelf. As a result, diatoms grew dramatically after light exposure, and Chaetoceros socialis complex highly contributed to the enhanced diatom abundance. Their photophysiological changes were also evident from the maximum quantum efficiency (Fv/Fm) of photochemistry in photosystem II, 13C-based photosynthetic-energy (PE) parameters, diadinoxanthin (DD)-diatoxanthin (DT) pool size, and the de-epoxidation state (DES) of DD. Even after the excess light exposure suppressed the photosynthetic activity in the microalgal cells, the diatoms recovered quickly, indicating the high photophysiological plasticity to dynamic light changes. Therefore, our results suggest that diatoms in surface sediments have a high seeding potential for blooms in the Pacific Arctic shelf region.
  • Fukai, Yutaka, Chiba, Sanae, Batten, Sonia, Sasaki, Yuka, Matsuno, Kohei, Richardson, Anthony J, Yamaguchi, Atsushi
    Bulletin of Fisheries Sciences, Hokkaido University 72 (2) 17 - 26 2022/08/22 [Not refereed][Not invited]
  • Daiki Kojima, Yusuke Hamao, Kanako Amei, Yutaka Fukai, Kohei Matsuno, Yoko Mitani, Atsushi Yamaguchi
    Deep Sea Research Part I: Oceanographic Research Papers 185 103771 - 103771 0967-0637 2022/07 [Refereed][Not invited]
  • Fumihiko Kimura, Kohei Matsuno, Yoshiyuki Abe, Atsushi Yamaguchi
    Frontiers in Marine Science 9 2022/02/22 [Refereed][Not invited]
     
    A remarkable early sea-ice reduction event was observed in the northern Bering Sea during 2018. In turn, this unusual hydrographic phenomenon affected several marine trophic levels, resulting in delayed phytoplankton blooms, phytoplankton community changes, and a northward shift of fish stocks. However, the response of the zooplankton community remains uncharacterized. Therefore, our study sought to investigate the zooplankton community shifts in the northern Bering Sea during the summers of 2017 and 2018 and evaluate the effects of early sea-ice melt events on the zooplankton community, population structure of large copepods, and copepod production. Five zooplankton communities were identified based on cluster analysis. Further, annual changes in the zooplankton community were identified in the Chirikov Basin. In 2017, the zooplankton community included abundant Pacific copepods transported by the Anadyr water. In 2018, however, the zooplankton community was dominated by small copepods and younger stages of large copepods (Calanus glacialis/marshallae and Metridia pacifica), which was likely caused by reproduction delays resulting from the early sea-ice reduction event. These environmental abnormalities increased copepod production; however, this higher zooplankton productivity did not efficiently reach the higher trophic levels. Taken together, our findings demonstrated that zooplankton community structure and production are highly sensitive to the environmental changes associated with early sea-ice reduction (e.g., warm temperatures and food availability).
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  • Nao Sato, Koki Tokuhiro, Kohei Matsuno
    Bull. Plankton Soc. Japan 69 (1) 11 - 17 2022/02 [Refereed][Not invited]
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  • Yusuke Hamao, Kohei Matsuno, Yoko Mitani, Atsushi Yamaguchi
    Journal of Oceanography 78 (2) 89 - 101 0916-8370 2022/01/27 [Refereed][Not invited]
     
    AbstractThe southern part of the Okhotsk Sea off Hokkaido has rich fishery resources supported by high primary production. The phytoplankton community has been described by several studies based on size-fractionated chlorophyll a concentration and primary production; however, the details of the species composition of nano- and micro-protist communities have not been well investigated. We evaluated the spatial distribution and relationship with hydrography of nano- and micro-protist communities in the southern region of the Okhotsk Sea off Hokkaido during the summer of 2019. Forty-two species of diatoms from 19 genera, dinoflagellates from 7 genera, tintinnid ciliates, oligotrich ciliates, and 1 genus of silicoflagellates were identified. Their spatial distribution showed distinct differences among the taxa. Cluster analysis based on the protist cell density identified six groups with geographically well-distinguished distributions. Diatom-dominant communities were distributed in the Cold Water Belt and Soya warm current along the coastal area of Hokkaido. Nanoflagellate-dominated communities were distributed in the offshore area. Some harmful species of diatoms (Pseudonitzschia pseudodelicatissima) and dinoflagellates (Alexandrium spp.) were dominant in the Cold Water Belt off Wakkanai. We suggest that the upwelling of cold water could increase the abundance of harmful species, with immanent negative impacts on marine ecosystems or fishery resources. In summary, the species composition and abundance of the summer protist community was strongly related to different water masses in the southern part of the Okhotsk Sea off Hokkaido.
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  • Yuri Fukai, Kohei Matsuno, Amane Fujiwara, Koji Suzuki, Mindy L. Richlen, Evangeline Fachon, Donald M. Anderson
    Journal of Geophysical Research: Oceans 126 (7) 2169-9275 2021/07 [Refereed][Not invited]
  • Nobuharu Inaba, Takuma Matsumoto, Hiroshi Kawai, Yuji Anaguchi, Kohei Matsuno
    Frontiers in Marine Science 8 2021/06/22 [Refereed][Not invited]
     
    The predation of commercially important Japanese sea cucumber Apostichopus japonicus by the kelp crab Pugettia ferox, widely distributed in coastal northeast Asia, was examined in field sampling and laboratory experiments. The ossicles of A. japonicus were detected from the stomach contents of a natural population of P. ferox at the rate of 32.4% of 68 individuals collected within artificial intermediate sea cucumber reefs for releasing hatchery-produced juveniles in December 2018. In the following laboratory experiments, a high mortality rate (7.7 ± 2.4 individuals day–1) of juvenile A. japonicus (15.35 ± 2.47 mm) was observed despite the different sizes and sex of P. ferox tested. It was also confirmed that a maximum of five sea cucumbers was killed and cut into small pieces within the first 2 h. Smaller and younger P. ferox individuals (adolescent) between carapace widths of 14.2–17.8 mm actively decorated themselves using pieces of chopped sea cucumber after feeding. Attached pieces of sea cucumber were observed to be fully eaten within a week, suggesting a possible strategy by P. ferox of short-term food storage as well as mimicry. This study demonstrates considerable evidence that predation mortality by sufficiently mobile P. ferox on commercially important A. japonicus can be significant, causing high mortality at the early life stage in the natural environment, especially in areas releasing hatchery-produced juveniles. It is also worth noting that the utilization of freshly chopped sea cucumbers as decoration material and food storage is a unique and novel ecological trait of P. ferox.
  • Makoto Sampei, Louis Fortier, Patrick Raimbault, Kohei Matsuno, Yoshiyuki Abe, Bernard Quéguiner, Augustin Lafond, Marcel Babin, Toru Hirawake
    Elementa: Science of the Anthropocene 9 (1) 2325-1026 2021/06/11 [Refereed][Not invited]
     
    This study aimed to quantify the impact of copepod grazing on the productivity of phytoplankton during an under sea-ice spring phytoplankton bloom (USPB) in western Baffin Bay. To quantify positive and/or negative impacts of copepod grazing on primary production and the interaction between copepod grazing and phytoplankton species, we sampled seawater and zooplankton under the landfast sea ice every 2–3 days between May 24 and July 10, 2016. Samples were analyzed for estimation of primary production, chlorophyll-a (chl-a) concentration, diatom abundance, and copepod fecal pellet (FP) production/grazing rate. Analyses of chl-a concentration, primary production, and FP production/grazing rate revealed clear temporal changes and a mismatch between primary production and copepod consumption. The FP production/grazing rate reached a maximum (9.4/31.2 mg C m–2 d–1) on June 16 before the USPB phase and suddenly decreased to 0.7/2.4 mg C m–2 d–1 on June 21, despite an increase in primary production to 74.0 mg C m–2 d–1. The copepod grazing rate (3.7 mg C m–2 d–1) was low relative to primary production (344.6 mg C m–2 d–1) during the USPB phase (after June 20). While our estimates illustrate that copepod grazing did not limit the maximum daily primary production during the USPB, the low grazing pressure (2% of primary production) may have been an additional contributor to the reduction in total primary productivity at the end of the USPB period due primarily to the low supply of regenerated nitrogen-containing nutrients to drive regenerated production.
  • Shin Sugiyama, Naoya Kanna, Daiki Sakakibara, Takuto Ando, Izumi Asaji, Ken Kondo, Yefan Wang, Yoshiki Fujishi, Shungo Fukumoto, Evgeniy Podolskiy, Yasushi Fukamachi, Minori Takahashi, Sumito Matoba, Yoshinori Iizuka, Ralf Greve, Masato Furuya, Kazutaka Tateyama, Tatsuya Watanabe, Shintaro Yamasaki, Atsushi Yamaguchi, Bungo Nishizawa, Kohei Matsuno, Daiki Nomura, Yuta Sakuragi, Yoshimasa Matsumura, Yoshihiko Ohashi, Teruo Aoki, Masashi Niwano, Naotaka Hayashi, Masahiro Minowa, Guillaume Jouvet, Eef van Dongen, Andreas Bauder, Martin Funk, Anders Anker Bjørk, Toku Oshima
    Polar Science 27 100632 - 100632 1873-9652 2021/03 [Refereed][Not invited]
     
    Environments along the coast of Greenland are rapidly changing under the influence of a warming climate in the Arctic. To better understand the changes in the coastal environments, we performed researches in the Qaanaaq region in northwestern Greenland as a part of the ArCS (Arctic Challenge for Sustainability) Project. Mass loss of ice caps and marine-terminating outlet glaciers were quantified by field and satellite observations. Measurements and sampling in fjords revealed the important role of glacial meltwater discharge in marine ecosystems. Flooding of a glacial stream in Qaanaaq and landslides in a nearby settlement were investigated to identify the drivers of the incidents. Our study observed rapid changes in the coastal environments, and their critical impact on the society in Qaanaaq. We organized workshops with the residents to absorb local and indigenous knowledge, as well as to share the results and data obtained in the project. Continuous effort towards obtaining long-term observations requiring involvement of local communities is crucial to contribute to a sustainable future in Greenland.
  • Takuma Matsumoto, Kohei Matsuno, Seiji Katakura, Hiromi Kasai, Atsushi Yamaguchi
    Regional Studies in Marine Science 43 101683 - 101683 2352-4855 2021/03 [Refereed][Not invited]
  • Atsushi Yamaguchi, Fumihiko Kimura, Yuri Fukai, Yoshiyuki Abe, Kohei Matsuno, Atsushi Ooki, Toru Hirawake
    Polar Science 27 100555 - 100555 1873-9652 2021/03 [Refereed][Not invited]
     
    In the northern Bering Sea, ice coverage and retreat timing were low and early, respectively, in the 2017?2018 winter. To evaluate the effect of these anomalous ice conditions, we quantified various environmental parameters (temperature, salinity, mixed-layer depth, nutrients) and the standing stocks of various planktonic taxa (phytoplankton counts, meso- and macrozooplankton mass, jellyfish abundance) during July of 2017 and 2018. For each year, the interaction between each parameter was evaluated by structural equation modelling (SEM) analysis. Large yearly differences were detected for the interactions between environmental parameters and planktonic stocks. Thus, for 2017, a total of fifteen interactions were present between environmental parameters and various planktonic stocks. In 2018, however, only eight interactions were present. Among the interactions, four were common to the two years. It is notable that the path coefficients of these four interactions were all lower in 2018 than in 2017. These findings suggest that the small magnitude and short pulse of the phytoplankton bloom in 2018 may have failed to transfer production and energy to a higher trophic level even within the planktonic food web. Indeed, in 2018, mass mortality was reported for seabirds (two murre species) feeding on planktivorous fishes.
  • Fumihiko Kimura, Yoshiyuki Abe, Kohei Matsuno, Russell R. Hopcroft, Atsushi Yamaguchi
    Deep Sea Research Part II: Topical Studies in Oceanography 181-182 104901 - 104901 0967-0645 2020/12 [Refereed][Not invited]
  • Yuri Fukai, Yoshiyuki Abe, Kohei Matsuno, Atsushi Yamaguchi
    Deep Sea Research Part II: Topical Studies in Oceanography 181-182 104903 - 104903 0967-0645 2020/12 [Refereed][Not invited]
  • Marie Maekakuchi, Kohei Matsuno, Jun Yamamoto, Yoshiyuki Abe, Atsushi Yamaguchi
    Deep Sea Research Part II: Topical Studies in Oceanography 181-182 104818 - 104818 0967-0645 2020/12 [Refereed][Not invited]
  • Inaba, N, I. Kodama, S. Nagai, T. Shiraishi, K. Matsuno, A. Yamaguchi, I. Imai
    Applied Science 10 (16) 5658 - 5658 2020/08 [Refereed][Not invited]
     
    The intensity and frequency of harmful algal blooms (HABs) have increased, posing a threat to human seafood resources due to massive kills of cultured fish and toxin contamination of bivalves. In recent years, bacteria that inhibit the growth of HAB species were found to be densely populated on the biofilms of some macroalgal species, indicating the possible biological control of HABs by the artificial introduction of macroalgal beds. In this study, an artificially created Ulva pertusa bed using mobile floating cages and a natural macroalgal bed were studied to elucidate the distribution of algal growth-limiting bacteria (GLB). The density of GLB affecting fish-killing raphidophyte Chattonella antiqua, and two harmful dinoflagellates, were detected between 106 and 107 CFU g−1 wet weight on the biofilm of artificially introduced U. pertusa and 10 to 102 CFU mL−1 from adjacent seawater; however, GLB found from natural macroalgal species targeted all tested HAB species (five species), ranging between 105 and 106 CFU g−1 wet weight in density. These findings provide new ecological insights of GLB at macroalgal beds, and concurrently demonstrate the possible biological control of HABs by artificially introduced Ulva beds.
  • Jee-Hoon Kim, Kyoung-Ho Cho, Hyoung Sul La, Eun Jung Choy, Kohei Matsuno, Sung-Ho Kang, Won Kim, Eun Jin Yang
    Frontiers in Marine Science 7 2020/07/22 [Refereed][Not invited]
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  • Review of spatial and inter-annual changes in the zooplankton community structure in the western Arctic Ocean during summers of 2008–2017
    Abe, Y, K. Matsuno, A. Fujiwara, A. Yamaguchi
    Progress in Oceanography 186 102391 - 102391 2020/06 [Refereed][Not invited]
  • Koki Tokuhiro, Yoshiyuki Abe, Jonaotaro Onodera, Makoto Sampei, Amane Fujiwara, Naomi Harada, Kohei Matsuno, Eva-Maria Nöthig, Atsushi Yamaguchi
    Polar Science 24 100509 - 100509 1873-9652 2020/06 [Refereed][Not invited]
  • K Matsuno, N Kanna, S Sugiyama, A Yamaguchi, EJ Yang
    Marine Ecology Progress Series 642 55 - 65 0171-8630 2020/05/28 [Refereed][Not invited]
     
    To evaluate the effects of meltwater discharge from marine-terminating glaciers on a fjord protist community in northwestern Greenland during summer, we investigated the distribution, abundance and biomass of the protist community and their relationships with hydrographic parameters. In the standing stock of protists, dinoflagellates (46.4%) and oligotrich ciliates (39.5%) were dominant throughout the study region. With respect to vertical distribution, oligotrich ciliates were abundant in the surface layer, mainly due to suitable food conditions (abundance of diatom and nanoflagellates). Near glaciers, relatively high chlorophyll a (chl a) concentrations were found in the subsurface layers associated with the low-temperature, high-turbidity and slightly high nutrient levels, indicating that the nutrient inputs from the upwelling glacial meltwater plume increased primary production. Large-sized Protoperidium spp. were found only at stations near glaciers where nutrients were abundant, and heterotrophic dinoflagellates showed strong relationships with nanoflagellates. These findings suggest that the upwelling associated with subglacial meltwater discharge can stimulate nanoflagellate production, resulting in increases in ciliate and heterotrophic dinoflagellate production.
  • Kohei Matsuno, Jake R. Wallis, So Kawaguchi, Sophie Bestley, Kerrie M. Swadling
    Deep Sea Research Part II: Topical Studies in Oceanography 174 104788 - 104788 0967-0645 2020/04 [Refereed][Not invited]
  • Tamechika, M.M., K. Matsuno, S. Wada, Y.Yusa
    Ecology and Evolution Wiley 10 (5) 2492 - 2498 2045-7758 2020/02 [Refereed][Not invited]
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  • The community composition of diatom resting stages in sediments of the northern Bering Sea in 2017 and 2018: the relationship to the interannual changes in the extent of the sea ice
    Fukai, Y, K. Matsuno, A. Fujiwara, A. Yamaguchi
    Polar Biology 42 1915 - 1922 2019/10 [Refereed][Not invited]
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  • Surface zooplankton size and taxonomic composition in Bowdoin Fjord, north-western Greenland: A comparison of ZooScan, OPC and microscopic analyses
    Naito⁠, A, Y. Abe, K. Matsuno, B. Nishizawa, N. Kanna, S. Sugiyama, A. Yamaguchi
    Polar Science 19 120 - 129 2019/03 [Refereed][Not invited]
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  • Yearly comparison of the planktonic chaetognath community in the Chukchi Sea in the summers of 1991 and 2007
    Amano, K, Y. Abe, K. Matsuno, A. Yamaguchi
    Polar Science 19 112 - 119 2019/03 [Refereed][Not invited]
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  • Tokuhiro, K, Y. Abe, K. Matsuno, J. Onodera, A. Fujiwara, N. Harada, T. Hirawake, A. Yamaguchi
    Polar Science 19 94 - 111 1873-9652 2019/03 [Refereed][Not invited]
     
    In recent years, marine ecosystems have changed due to the drastic sea ice reduction in the Arctic Ocean, but the relationship between copepod phenology and environmental drivers is unclear. To reveal the relationship, seasonal changes in the flux (abundance of swimmers), population structure, lipid accumulation and gonad maturation of four dominant copepods (Calanus hyperboreus, Metridia longa, Paraeuchaeta glacialis and Heterorhabdus norvegicus) were studied using a sediment trap deployed at a depth of 222 m in the Pacific-Arctic sector from October 2010 to September 2013. C. hyperboreus, mostly comprising copepodid stage 6 females (C6F), exhibited several peaks in flux in spring and autumn. C. hyperboreus C6Fs were dominated by lipid-rich specimens year-round, and gonad development was observed in these samples from February to April. The M. longa flux showed no clear seasonality. Gonad maturation of M. longa C6Fs occurred from February to September. P. glacialis flux exhibited two peaks in autumn of 2011 and 2012. In contrast to the former two species, lipid-rich, mature P. glacialis C6Fs occurred year-round. H. norvegicus copepodid stage 6 males (C6Ms) also occurred throughout the year, likely because H. norvegicus has functional feeding appendages, even in C6Ms. From generalized additive models, C. hyperboreus, M. longa and P. glacialis showed relationships with daytime length and/or sea ice concentrations, but the relationship patterns were different. These findings suggest that the response (e.g., vertical migration) to the environmental parameters could vary with species and the drastic sea ice reductions may affect the copepod phenology in the Pacific-Arctic sector.
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  • Impact of sea-ice reduction on the plankton community in the Pacific sector of the Arctic Ocean
    Matsuno Kohei
    Oceanography in Japan 27 (6) 217 - 230 2018/12 [Refereed][Invited]
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  • Distribution of viable resting stage cells of diatoms in sediments and water columns of the Chukchi Sea, Arctic Ocean
    Tsukazaki, C, K.-I. Ishii, K. Matsuno, A. Yamaguchi, I. Imai
    Phycologia 57 440 - 452 2018/06 [Refereed][Not invited]
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  • Amane Fujiwara, Shigeto Nishino, Kohei Matsuno, Jonaotaro Onodera, Yusuke Kawaguchi, Toru Hirawake, Koji Suzuki, Jun Inoue, Takashi Kikuchi
    Polar Biology 41 (6) 1279 - 1295 0722-4060 2018/06/01 [Refereed][Not invited]
     
    The recent increasing of atmospheric turbulence has had considerable impact on the oceanic environment and ecosystems of the Arctic. To understand its effect on phytoplankton community structure, a Eulerian fixed-point observation (FPO) was conducted on the Chukchi shelf in fall 2013. Temporal and vertical distributions of the phytoplankton community were inferred from algal pigment signatures. A strong wind event (SWE) occurred during the observation term, and significant convection supplied nutrients from the bottom layer to the surface. Before the SWE, pigment composition in the warmer, less saline, and nutrient-poor surface waters was diverse with low concentration of chlorophyll-a (chla). Vertical mixing induced by the SWE weakened the stratification and brought sufficient nutrients to enhance diatom-derived pigment concentrations (e.g., fucoxanthin and chlc3), suggesting increases in diatoms. We also developed a model to predict the distribution of major phytoplankton pigment/chla ratios using a profiling multi-wavelength fluorometer (Multi-Exciter) with higher spatio-temporal resolution. The Multi-Exciter also captured changes in pigment composition with environmental changes at the FPO site and at four observation sites 16 km from the location of the FPO. Furthermore, we investigated the change in grazing rates of the major Arctic copepod Calanus glacialis copepodid stage five to assess the interaction between primary and secondary producers during the fall bloom. Increased diatom biomass caused a significant increase in the grazing rate on microphytoplankton (>  20 µm) and a decrease on nanophytoplankton (2–20 µm), indicative of a strong cascade effect because of the reduction of microzooplankton due to the grazing from C. glacialis. We conclude that SWEs during fall might affect food webs via the alternation of seasonal succession of phytoplankton community structure.
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  • Jose M. Landeira, Kohei Matsuno, Yuji Tanaka, Atsushi Yamaguchi
    Polar Science 16 86 - 89 1873-9652 2018/06 [Refereed][Not invited]
     
    © 2018 In the Bering Sea, warming and reduction of summer sea-ice cover are driving species ranges towards the Arctic. Tanner crab, Chionoecetes bairdi, is a commercially important species in the SE Bering Sea with a northerly range margin in 62ºN. In this paper, using plankton samples collected in the Pacific sub-Arctic/Arctic sector during summer, we report for the first time the presence of larval stages (zoea II) of C. bairdi far from its northern limit of the distribution, in the south of St. Lawrence Island during 1991, and even crossing the Bering Strait into the Chukchi Sea during 1992. We suggest that the long planktonic phase (3–5 months), in combination with the oceanographic circulation, may facilitate eventual long-distance transport.
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  • Hikaru Hikichi, Daichi Arima, Yoshiyuki Abe, Kohei Matsuno, Soshi Hamaoka, Seiji Katakura, Hiromi Kasai, Atsushi Yamaguchi
    Regional Studies in Marine Science 20 34 - 44 2352-4855 2018/04/01 [Refereed][Not invited]
     
    To evaluate the temporal changes in zooplankton size spectra, optical plankton counter (OPC) measurements were made of high-frequency time-series zooplankton samples collected at approximately 3.5-day intervals in Mombetsu Harbour, which is located in the southern Okhotsk Sea, from January to December 2011. Based on biomasses of 47 equivalent spherical diameter (ESD) size classes binned at 0.1 mm intervals across 0.35–5 mm, the Bray–Curtis similarity index separated the zooplankton community into six groups (A–F). The occurrence of each group was separated seasonally. Thus, groups A and B were observed during the ice-covered season and summer season, respectively. During March and June, groups C–F were observed. Their occurrence varied in the short term in relation to the exchange of water masses. Groups A and C, which were observed from January to April, showed flatter normalized biomass size spectra (NBSS) slopes (−0.85 to −1.1), which indicate low productivity. In contrast, the other groups showed steeper slopes (−1.31 to −1.52) from May to December, with high productivity. Throughout the year, the frequency of highly productive groups occurred at a high level (95.2%). Although the seasonal variability in zooplankton size and productivity in Mombetsu Harbour was mainly governed by water mass exchanges, the productivity was continuously high throughout nearly all of the one-year study period.
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  • Masafumi Natsuike, Rui Saito, Amane Fujiwara, Kohei Matsuno, Atsushi Yamaguchi, Naonobu Shiga, Toru Hirawake, Takashi Kikuchi, Shigeto Nishino, Ichiro Imai
    PLOS ONE 12 (11) e0188565  1932-6203 2017/11 [Refereed][Not invited]
     
    The eastern Bering Sea has a vast continental shelf, which contains various endangered marine mammals and large fishery resources. Recently, high numbers of toxic A. tamarense resting cysts were found in the bottom sediment surface of the eastern Bering Sea shelf, suggesting that the blooms have recently occurred. However, little is known about the presence of A. tamarense vegetative cells in the eastern Bering Sea. This study's goals were to detect the occurrence of A. tamarense vegetative cells on the eastern Bering Sea shelf and to find a relationship between environmental factors and their presence. Inter-annual field surveys were conducted to detect A. tamarense cells and environmental factors, such as nutrients, salinity, chlorophyll a, and water temperature, along a transect line on the eastern Bering Sea shelf during the summers of 2004, 2005, 2006, 2009, 2012, and 2013. A. tamarense vegetative cells were detected during every sampling year, and their quantities varied greatly from year to year. The maximum cell densities of A. tamarense observed during the summers of 2004 and 2005 were much higher than the Paralytic shellfish poisoning warning levels, which are greater than 100-1,000 cells L-1, in other subarctic areas. Lower quantities of the species occurred during the summers of 2009, 2012, and 2013. A significant positive correlation between A. tamarense quantity and water temperature and significant negative correlations between A. tamarense quantity and nutrient concentrations (of phosphate, silicate, and nitrite and nitrate) were detected in every sampling period. The surface- and bottom-water temperatures varied significantly from year to year, suggesting that water temperatures, which have been known to affect the cell growth and cyst germination of A. tamarense, might have affected the cells' quantities in the eastern Bering Sea each summer. Thus, an increase in the Bering Sea shelf's water temperature during the summer will increase the frequency and scale of toxic blooms and the toxin contamination of plankton feeders. This poses serious threats to humans and the marine ecosystem.
  • Jose M. Landeira, Kohei Matsuno, Atsushi Yamaguchi, Toru Hirawake, Takashi Kikuchi
    POLAR BIOLOGY 40 (9) 1805 - 1819 0722-4060 2017/09 [Refereed][Not invited]
     
    Crustacean decapods are key components that structure the benthic ecosystems in the Subarctic/Arctic regions and support one of the largest fishery industries, but their larval dynamics are largely unknown. To investigate variability in decapod larvae community in this region, we analysed plankton samples collected during the summers of 2007 and 2008 along the southeastern Bering and Chukchi Seas. Distribution of adult population was studied using bottom trawling during 2008 cruise. Larvae of Pagurus spp., Hyas spp., and the commercially important Chionoecetes bairdi and Chionoecetes opilio were the most abundant species. The distribution of benthic adults linked to those of planktonic larvae and may favour recruitment near suitable habitats and the maintenance of the populations. Earlier larval stages of C. bairdi, C. opilio, and Hyas spp. were more abundant in 2008 than in 2007. The body size of C. opilio showed a significant latitudinal pattern, in which larger sizes occurred at higher latitudes in association with distinct temperature and food conditions. We argue that annual changes in abundance and developmental stage structure of planktonic larvae seemed to be related to the 1 month delay in the sampling period and are not determined by the contrasting environmental conditions observed in both years.
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  • Masafumi Natsuike, Hiroshi Oikawa, Kohei Matsuno, Atsushi Yamaguchi, Ichiro Imai
    HARMFUL ALGAE 63 13 - 22 1568-9883 2017/03 [Refereed][Not invited]
     
    Abundant cyst distributions of the toxic dinoflagellate Alexandrium fundyense (previous A. tamarense north American Glade) were recently observed on the north Chukchi Sea shelf and on the eastern Bering Sea shelf, suggesting that A. fundyense is both highly adapted to the local environments in the high latitude areas and might cause toxin contamination of plankton feeders. However, little is known about the physiological characteristics and toxin profiles of A. fundyense in these areas, which are characterized by low water temperatures, weak sunlight, and more or less permanent ice cover during winter. To clarify the physiological characteristics of A. fundyense, the effects of water temperature and light intensity on the vegetative growth and toxin profiles of this species were examined using A. fundyense strains isolated from one sediment sample collected from each area. Using the same sediments samples, seasonal changes of the cyst germination in different water temperatures were investigated. Vegetative cells grew at temperatures as low as 5 degrees C and survived at 1 degrees C under relatively low light intensity. They also grew at moderate water temperatures (10-15 degrees C). Their cysts could germinate at low temperatures (1 degrees C) and have an endogenous dormancy period from late summer to early spring, and warmer water temperatures (5-15 degrees C) increased germination success. These physiological characteristics suggest that A. fundyense in the Chukchi Sea and eastern Bering Sea is adapted to the environments of high latitude areas. In addition, the results suggest that in the study areas A. fundyense has the potential to germinate and grow when water temperatures increase. Cellular toxin amounts of A. fundyense strains from the eastern Bering Sea and Chukchi Sea were ranged from 7.2 to 38.2 fmol cell(-1). These toxin amounts are comparable with A. fundyense strains isolated from other areas where PSP toxin contamination of bivalves occurs. The dominant toxin of the strains isolated from the Chukchi Sea was saxitoxin, while mostA.fundyense strains from the eastern Bering Sea are dominated by the C2 toxin. Toxin profiles similar to those detected in Chukchi Sea have not been reported by any previous research. The dominance of a highly toxic PST variant in Chukchi A. fundyense suggests that presence of the species at low cell concentrations may cause toxin contamination of predators. This study revealed that abundant A. fundyense cysts deposited on the eastern Bering Sea and Chukchi Sea shelves potentially germinate and grow with PSP toxin contents in the local environments. In conclusion, a high risk of PSP occurrences exists on the eastern Bering Sea and Chukchi Sea shelves. (C) 2017 Elsevier B.V. All rights reserved.
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  • Asami Nakamura, Kohei Matsuno, Yoshiyuki Abe, Hiroshi Shimada, Atsushi Yamaguchi
    ZOOLOGICAL STUDIES 56 (13) 1021-5506 2017 [Refereed][Not invited]
     
    While length-weight (L-W) regressions for warm-water zooplankton taxa from the waters neighbouring Japan already exist, they are still missing for comparable cold-water species. In this study, the L-W regressions of 41 species belonging to 12 taxa that are dominant in the Oyashio region were reported. The body length and volume of zooplankton were measured with an image-analysis system, and the effects of lipid accumulation in Copepoda on their mass and chemical composition were quantified. The L-W regressions had a high coefficient of determination (mean r(2) = 0.886). For the chemical composition, the water composition ranged from 69.8 to 95.2% wet mass (WM), carbon (C) composition from 3.8 to 60.8% dry mass (DM) and nitrogen (N) composition from 1.0 to 10.1% DM. Taxon-specific differences in the chemical composition were marked for the gelatinous taxa (Appendicularia, Cnidaria, Salpida), which also had high water and low C composition. Because C is an index of lipids, high water compositions together with low lipid compositions are considered to be characteristics of the gelatinous taxa. The most significant effects of lipid accumulation in the Copepoda are changes in DM and C. Within the same developmental stage, the DM and C compositions of the full lipid-containing specimens showed 495% and 741% increases, respectively, over those of the low lipid-containing specimens. These differences exceeded the changes after moulting (78.1%) for general copepod species. Thus, lipid accumulation should be evaluated for the accurate mass estimation of boreal Copepoda by image analysis.
  • A. Yamaguchi, K. Matsuno, Y. Abe, D. Arima, I. Imai
    PROGRESS IN OCEANOGRAPHY 150 13 - 19 0079-6611 2017/01 [Refereed][Not invited]
     
    A total of 100 mesozooplankton samples collected with NORPAC nets from a 0 to 150-m depth at latitudinal stations (35-44 degrees N) along 155 degrees E each May from 2002 through 2011 were analyzed. The mesozooplankton abundance at each station varied from 39 to 1106 ind. m(-3). The mesozooplankton biomass was consistently higher (80-100 mg DM m(-3)) in the transition domain (40-42 degrees N) than the biomass in the other domains. An empirical metabolic rate-based carbon budget model indicated that production of mesozooplankton suspension feeders was highest (120-175 mg C m(-2) d(-1)) in the transition domain. A comparison between the production of the mesozooplankton suspension feeders and the food requirement of mesozooplankton carnivores indicated that the latter was well fulfilled by the former in the subarctic and transition domains. However, the food requirement of the mesozooplankton carnivores was near equal to or exceeded the production of mesozooplankton suspension feeders in the subtropical domain. As an annual event, the feeding migration of epipelagic fish to the transition and subarctic domains in summer may be interpreted by their utilization of the excess secondary production (production of mesozooplankton suspension feeders). (C) 2015 Elsevier Ltd. All rights reserved.
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  • Bungo Nishizawa, Kohei Matsuno, Elizabeth A. Labunski, Kathy J. Kuletz, Atsushi Yamaguchi, Yutaka Watanuki
    BIOGEOSCIENCES 14 (1) 203 - 214 1726-4170 2017/01 [Refereed][Not invited]
     
    The short-tailed shearwater (Ardenna tenuirostris) is one of the abundant marine top predators in the Pacific; this seabird spends its non-breeding period in the northern North Pacific during May-October and many visit the southern Chukchi Sea in August-September. We examined potential factors affecting this seasonal pattern of distribution by counting short-tailed shearwaters from boats. Their main prey, krill, was sampled by net tows in the southeastern Bering Sea/Aleutian Islands and in the Bering Strait/southern Chukchi Sea. Short-tailed shearwaters were mainly distributed in the southeastern Bering Sea/Aleutian Islands (60 +/- 473 birds km(-2)) in July 2013, and in the Bering Strait/southern Chukchi Sea (19 +/- 91 birds km(-2)) in September 2012. In the Bering Strait/southern Chukchi Sea, krill size was greater in September 2012 (9.6 +/- 5.0 mm in total length) than in July 2013 (1.9 +/- 1.2 mm). Within the Bering Strait/southern Chukchi Sea in September 2012, short-tailed shearwaters occurred more frequently in cells (50 +/- 50 km) where large-sized krill were more abundant. These findings, and information previously collected in other studies, suggest that the seasonal northward movement of short-tailed shearwaters might be associated with the seasonal increase in krill size in the Bering Strait/southern Chukchi Sea. We could not, however, rule out the possibility that large interannual variation in krill abundance might influence the seasonal distribution of shearwaters. This study highlights the importance of krill, which is advected from the Pacific, as an important prey of top predators in the Arctic marine ecosystem.
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  • Masafumi Natsuike, Kohei Matsuno, Toru Hirawake, Atsushi Yamaguchi, Shigeto Nishino, Ichiro Imai
    HARMFUL ALGAE 61 80 - 86 1568-9883 2017/01 [Refereed][Not invited]
     
    A high abundance of resting cysts of the toxic dinoflagellate Alexandrium tamarense was recently reported in the vast continental shelf of the Chukchi Sea in the Arctic Ocean, suggesting that the species is widespread in the shelf. Nevertheless, little is known about the occurrence of A. tamarense vegetative cells in the water column of the arctic. Sea ice reduction and the inflow of Pacific summer water (PSW) through the Bering Strait have recently increased owing to warming in the shelf. To determine the spatial and temporal distributions of A. tamarense in the Chukchi Sea shelf and their relationship to the inflow of PSW, field samplings were conducted in the Chukchi Sea and north Bering Sea shelves three times during the summer of 2013 from July to October. Vegetative cells of A. tamarense was detected in both shelves at all sampling periods with a maximum density of 3.55 x 10(3) cells L-1. This species was also observed at the station at 73 degrees N, indicating the northernmost record of this species to date. The center of the A. tamarense distribution was between the north Bering and south Chukchi Sea shelf during the first collection period, and spread to the north Chukchi Sea shelf during the second and third collection periods. The species occurrences were mainly observed at stations affected by the PSW, especially Bering shelf water. Water structure of PSW was characterized by warmer surface and bottom water temperatures, and increased temperatures may have promoted the cell growth and cyst germination of A. tamarense. Therefore, it is suggested that an increase in the PSW inflow owing to warming promotes toxic A. tamarense occurrences on the Chukchi Sea shelf. (C) 2016 Elsevier B.V. All rights reserved.
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  • Kohei Matsuno, Yoshiyuki Abe, Atsushi Yamaguchi, Takashi Kikuchi
    POLAR SCIENCE 10 (4) 503 - 510 1873-9652 2016/12 [Refereed][Not invited]
     
    In the Arctic Ocean, Calanus glacialis is the most dominant species in zooplankton biomass. While important, little information is available concerning the factors controlling their population. In this study, we evaluated regional patterns and environmental factors controlling the population structure of C. glacialis in the western Arctic Ocean in summer months (July-October) in 1991, 1992, 2007, 2008, 2010, 2012, 2013 and 2014. To evaluate regional patterns, environmental parameters (temperature, salinity and chlorophyll a) and C. glacialis population parameters (abundance, biomass, mean copepodid stage and lipid accumulation) were divided into three latitudinal regions. In all three regions from July to October, chlorophyll a decreased, while the mean copepodid stage increased. These results suggest phytoplankton blooms occurred early in the sampling period, and C. glacialis grew during the period. From Structural Equation Model (SEM) analysis, the controlling factors on the C. glacialis population were evaluated. The results of the SEM analysis indicated positive correlations between abundance and biomass; Julian day and mean copepodid stage; and temperature and mean copepodid stage. Additionally, a negative correlation between abundance and mean copepodid stage was observed. (C) 2016 Elsevier B.V. and NIPR. All rights reserved.
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  • Yoshiyuki Abe, Hiroomi Miyamoto, Rui Saito, Kohei Matsuno, Atsushi Yamaguchi, Ichiro Imai
    REGIONAL STUDIES IN MARINE SCIENCE 8 122 - 132 2352-4855 2016/11 [Refereed][Not invited]
     
    In the Oyashio region, the dominant water masses are switched at the surface layer within a short period during spring. Simultaneously, a large phytoplankton bloom is known to occur at the surface layer, and nearly half of the annual primary production is concentrated during spring. These drastic changes in the water mass and food condition are expected to strongly affect the macrozooplankton population dynamics. However, their effects on the chaetognath population remain unknown. To evaluate the effects of the water mass exchange and spring phytoplankton bloom, we analysed short-term changes in the population structure, growth rate, gut contents and predation impact of the three dominant chaetognaths (Eukrohnia hamata, Parasagitta elegansand Pseudosagitta scrippsae) in the Oyashio region during March-April 2007. Eleven samples were collected by a 0-200 m oblique tow of a Bongo net at night during 9 March to 30 April, 2007. The effects of the water mass exchange were significant for all three chaetognath species. During the sampling period, significant growth was observed for the two dominant species (E. hamata and P. elegans). The daily growth rate was 39-50 mu m day(-1) for E. hamata and 42-101 mu m day(-1) for P. elegans. The mean predation impact of P. elegans at 0-200 m was 0.194 no. prey consumed m(-3) day(-1) and that of P. scrippsae was 0.028 no. prey consumed m(-3) day(-1). These values corresponded with 0-0.097% (P. elegans) or 0-0.043% (P. scrippsae) of the total zooplankton abundance during the spring. (C) 2016 Published by Elsevier B.V.
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  • Kohei Matsuno, Jose M. Landeira Sanchez, Atsushi Yamaguchi, Toru Hirawake, Takashi Kikuchi
    POLAR SCIENCE 10 (3) 335 - 345 1873-9652 2016/09 [Refereed][Not invited]
     
    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. (C) 2016 Elsevier B.V. and NIPR.
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  • Hiroko Sasaki, Kohei Matsuno, Amane Fujiwara, Misaki Onuka, Atsushi Yamaguchi, Hiromichi Ueno, Yutaka Watanuki, Takashi Kikuchi
    BIOGEOSCIENCES 13 (15) 4555 - 4567 1726-4170 2016/08 [Refereed][Not invited]
     
    The advection of warm Pacific water and the reduction in sea ice in the western Arctic Ocean may influence the abundance and distribution of copepods, a key component of food webs. To quantify the factors affecting the abundance of copepods in the northern Bering and Chukchi seas, we constructed habitat models explaining the spatial patterns of large and small Arctic and Pacific copepods separately. Copepods were sampled using NORPAC (North Pacific Standard) nets. The structures of water masses indexed by principle component analysis scores, satellite-derived timing of sea ice retreat, bottom depth and chlorophyll a concentration were integrated into generalized additive models as explanatory variables. The adequate models for all copepods exhibited clear continuous relationships between the abundance of copepods and the indexed water masses. Large Arctic copepods were abundant at stations where the bottom layer was saline; however they were scarce at stations where warm fresh water formed the upper layer. Small Arctic copepods were abundant at stations where the upper layer was warm and saline and the bottom layer was cold and highly saline. In contrast, Pacific copepods were abundant at stations where the Pacific-origin water mass was predominant (i.e. a warm, saline upper layer and saline and a highly saline bottom layer). All copepod groups showed a positive relationship with early sea ice retreat. Early sea ice retreat has been reported to initiate spring blooms in open water, allowing copepods to utilize more food while maintaining their high activity in warm water without sea ice and cold water. This finding indicates that early sea ice retreat has positive effects on the abundance of all copepod groups in the northern Bering and Chukchi seas, suggesting a change from a pelagic-benthic-type ecosystem to a pelagic-pelagic type.
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  • Tsubasa Nakano, Kohei Matsuno, Bungo Nishizawa, Yuka Iwahara, Yoko Mitani, Jun Yamamoto, Yasunori Sakurai, Yutaka Watanuki
    POLAR BIOLOGY 39 (6) 1081 - 1086 0722-4060 2016/06 [Refereed][Not invited]
     
    To understand trophic responses of polar cod Boreogadus saida (a key species in Arctic food webs) to changes in zooplankton and benthic invertebrate communities (prey), we compared its stomach contents and body condition between three regions with different environments: the northern Bering Sea (NB), southern Chukchi Sea (SC), and central Chukchi Sea (CC). Polar cod were sampled using a bottom trawl, and their potential prey species in the environment were sampled using a plankton net and a surface sediment sampler. Polar cod fed mainly on appendicularians in the NB and SC where copepods were the most abundant in the environment, while they fed on copepods, euphausiids, and gammarids in the CC where barnacle larvae were the most abundant species in plankton samples on average. The stomach fullness index of polar cod was higher in the NB and SC than CC, while their body condition index did not differ between these regions. The lower lipid content of appendicularians compared to other prey species is the most plausible explanation for this inconsistency.
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  • Takahito Ikenoue, Kjell R. Bjorklund, Paulian Dumitrica, Anders K. Krabberod, Katsunori Kimoto, Kohei Matsuno, Naomi Harada
    MARINE MICROPALEONTOLOGY 124 75 - 94 0377-8398 2016/04 [Refereed][Not invited]
     
    Radiolarians in the Arctic Ocean have been studied lately in both plankton and sediment trap samples in the Chukchi Sea area. These studies have shed light on new radiolarian taxa, especially within the order Entactinaria, including two new species of Joergensenium, Joergensenium arcticum from the western Arctic Ocean, so far restricted to the Pacific Winter Water in the Chukchi Sea, and Joergensenium clevei hitherto found in the northern part of the Norwegian Sea south of the Fram Strait. The taxonomic position of the order Entactinaria is discussed and the genus Joergensenium has been emended. We have also observed in detail the internal structure of Joergensenium arcticum using Microfocus X-ray Computed Tomography and have utilized three-dimensional imaging for the first time in a species description. (C) 2016 Elsevier B.V. All rights reserved.
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  • Yoshiyuki Abe, Yuichiro Yamada, Rui Saito, Kohei Matsuno, Atsushi Yamaguchi, Kosei Komatsu, Ichiro Imai
    REGIONAL STUDIES IN MARINE SCIENCE 3 154 - 162 2352-4855 2016/01 [Refereed][Not invited]
     
    Short-term changes in the population structure of dominant amphipods in the Oyashio region during the spring bloom were studied and discussed from the perspective of the effect of water mass change and the utilization of a phytoplankton bloom. Throughout the sampling period, amphipods belonging to 9 genera and 13 species were found. Among them, three amphipods (Cyphocaris challengeri, Primno abyssalis and Themisto pacifica) accounted for 89% of the total amphipod abundance and 92% of the biomass. For C. challengeri, the compositions of egg-and juvenile-carrying specimens within mature females were increased through April; juveniles exhibited a drastic increase in late April. These facts suggest that C. challengeri primarily achieved reproduction during the spring phytoplankton bloom. For P. abyssalis, growth of the mean body length was observed for each juvenile cohort. Thus, P. abyssalis achieved juvenile growth during the spring phytoplankton bloom. For T. pacifica, the compositions of egg-and juvenile-carrying females increased through April. These facts suggest that T. pacifica achieved maturation during the spring phytoplankton bloom. The effect of the water mass exchange on the amphipod population was more moderate than that observed on the other macrozooplankton taxa. This finding may be a result of a strong diel vertical migration behavior, which functions to maintain the population position. The species-specific differences in the amphipods in the utilization of spring phytoplankton may be related to the species-specific life cycle timing (phenology) in this region. (C) 2015 Elsevier B.V. All rights reserved.
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  • Naoya Yokoi, Kohei Matsuno, Mutsuo Ichinomiya, Atsushi Yamaguchi, Shigeto Nishino, Jonaotaro Onodera, Jun Inoue, Takashi Kikuchi
    BIOGEOSCIENCES 13 (4) 913 - 923 1726-4170 2016 [Refereed][Not invited]
     
    Recent studies indicate an increase in atmospheric turbulence in the Chukchi Sea due to the recent drastic sea-ice reduction during summer months. The importance of the effects of this atmospheric turbulence on the marine ecosystem in this region, however, is not fully understood. To evaluate the effects of atmospheric turbulence on the marine ecosystem, high-frequency sampling (daily) from five layers of the microplankton community between 0 and 30 m at a fixed station in the Chukchi Sea from 10 through 25 September 2013 was conducted. During the study period, a strong wind event (SWE) was observed on 18 and 19 September. The abundance of microplankton was 2.6 to 17.6 cells mL(-1), with a maximum abundance being reported at 20 m on 22 September, while diatoms were the most dominant taxa throughout the study period. The abundance of diatoms, dinoflagellates and ciliates ranged between 1.6 and 14.1, 0.5 and 2.4 and 0.1 and 2.8 cells mL(-1), respectively. Diatoms belonging to 7 genera consisting of 35 species (Cylindrotheca closterium and Leptocylindrus danicus were dominant), dinoflagellates belonging to 7 genera consisting of 25 species (Prorocentrum balticum and Gymnodinium spp. were dominant) and ciliates belonging to 7 genera consisting of 8 species (Strobilidium spp. and Strombidium spp. were dominant) were identified. Within the microplankton species, there were 11 species with abundances that increased after the SWE, while there was no species with an abundance that decreased following the SWE. It is conjectured that atmospheric turbulences, such as that of an SWE, may supply sufficient nutrients to the surface layer that subsequently enhance the small bloom under the weak stratification of the Chukchi Sea Shelf during the autumn months. After the bloom, the dominant diatom community then shifts from centric-dominated to one where centric/pennate are more equal in abundance.
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  • Daichi Arima, Kohei Matsuno, Atsushi Yamaguchi, Takahiro Nobetsu, Ichiro Imai
    CRUSTACEANA 88 (12-14) 1307 - 1321 0011-216X 2015/12 [Refereed][Not invited]
     
    The seasonal and inter-annual changes in the asymmetry of female insemination and the male leg 5 of the planktonic calanoid copepods Metridia okhotensis and M. pacifica were investigated in the Okhotsk Sea. An inter-species comparison of both parameters was also carried out on seven Metridia species collected from oceans throughout the world. For M. okhotensis from the Okhotsk Sea, most of the females showed left-side insemination (annual average: 95.7%) and most of the males showed left-side asymmetry (99.7%) of the long inner process of the second exopodal segment in the fifth leg throughout the year. However, sympatric M. pacifica showed different ratios of asymmetry for female insemination and male morphotypes with a left : right = 1 : 2 ratio throughout the year. For the seven Metridia species from the global oceans treated in this study, ratios of asymmetry for female insemination and male morphotypes were correlated with each other. One-sided insemination (i.e., only left or only right insemination) was a common pattern for various Metridia species from global oceans, but their ratios varied by species. Previously, low hatching rates (29-68%) of eggs were reported for various Metridia spp. in laboratory experiments, but the reasons for these low rates were unclear. Because each spermatheca of Metridia spp. is connected to the oviduct on the same side, either left or right, this suggests that half of the eggs produced by unilaterally inseminated females remain unfertilized. The morphology of the genital structures and literature data of the egg hatching rates of Metridia spp. indicate that almost half of the eggs produced by females are not viable and are, thus, wasted.
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  • Elizaveta A. Ershova, Russell R. Hopcroft, Ksenia N. Kosobokova, Kohei Matsuno, R. John Nelson, Atsushi Yamaguchi, Lisa B. Eisner
    OCEANOGRAPHY 28 (3) 100 - 115 1042-8275 2015/11 [Refereed][Not invited]
     
    The Chukchi Sea pelagic ecosystem, which is finely tuned to the region's seasonal ice formation and retreat, has been undergoing dramatic oceanographic change related to shifting sea ice cover and increasing temperatures over the last decades. We examine historical data sets on zooplankton communities in the central Chukchi Sea during the time period 1946 to 2012. Analysis is confounded by differences between years in terms of spatial coverage, seasonal variability, and methodology; nonetheless, trends remain detectable when a sufficient number of study years is compiled. In addition to high levels of interannual variability, we demonstrate that there have been significant increases in zooplankton biomass and abundance in recent years compared to historical studies, along with shifting distribution ranges for several key species. This signal is most pronounced for the copepods, particularly Calanus glacialis, which appears to be indirectly benefiting from warming of the region. While summer zooplankton communities of the Chukchi Sea have been primarily Bering-Pacific in character for as long as records exist, continuing warming and ice loss are increasing the influence of Bering-Pacific fauna within the Chukchi region.
  • Kohei Matsuno, Atsushi Yamaguchi, Amane Fujiwara, Jonaotaro Onodera, Eiji Watanabe, Naomi Harada, Takashi Kikuchi
    JOURNAL OF NATURAL HISTORY 49 (45-48) 2711 - 2726 0022-2933 2015/10 [Refereed][Not invited]
     
    Winter ice cover of the Arctic Ocean makes year-round zooplankton sampling by plankton net a difficult task. Therefore, the collection of copepods with a sediment trap can be a powerful tool. In the present study, we analysed the seasonal changes in the population structures of five dominant planktonic copepods (Oncaea parila, Calanus hyperboreus, Metridia longa, Paraeuchaeta glacialis and Heterorhabdus norvegicus), which were collected using a sediment trap rotated at 10-15day intervals moored at 184-260m in the Northwind Abyssal Plain (75 degrees 00N, 162 degrees 00W) of the western Arctic Ocean from October 2010 to September 2012. Oncaea parila C6F with egg sacs occurred throughout the year, and the total abundance and composition of early copepodid stages (C1-C3) had two peaks each year. Calanus hyperboreus was dominated by C6F throughout the year, and their maturation was observed during February to May. Metridia longa C6F had a clear seasonality in lipid accumulation and gonad maturation: high lipid accumulation was observed from October to February, whereas gonad maturation occurred from March to September. Paraeuchaeta glacialis C6F also showed seasonality in lipid accumulation and gonad maturation, although their seasonal patterns varied from those of M. longa: high lipid individuals were abundant from February to April and mature individuals dominated from October to November. Heterorhabdus norvegicus showed seasonal changes in population structure as well: C1, C5, and C6M dominated from April to May, November to February and August to October, respectively. The life cycle patterns of these species are compared with those reported from other areas. While the results obtained by a sediment trap are inevitably subject to collection bias (i.e. passive collection at a fixed depth), a sediment trap should be considered as a powerful tool for the evaluation of the life cycle of planktonic copepods, especially in ice-covered oceans.
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  • Eiji Watanabe, Jonaotaro Onodera, Naomi Harada, Makio C. Honda, Katsunori Kimoto, Takashi Kikuchi, Shigeto Nishino, Kohei Matsuno, Atsushi Yamaguchi, Akio Ishida, Michio J. Kishi
    NATURE COMMUNICATIONS 6 8441  2041-1723 2015/09 [Refereed][Not invited]
  • K. Matsuno, A. Yamaguchi, S. Nishino, J. Inoue, T. Kikuchi
    BIOGEOSCIENCES 12 (13) 4005 - 4015 1726-4170 2015/07 [Refereed][Not invited]
     
    To evaluate the effect of atmospheric turbulence on a marine ecosystem, high-frequency samplings (two to four times per day) of a mesozooplankton community and the gut pigment of dominant copepods were performed at a fixed station in the Chukchi Sea from 10 to 25 September 2013. During the study period, a strong wind event (SWE) was observed on 18 September. After the SWE, the biomass of chlorophyll a (Chl a) increased, especially for micro-size (> 10 mu m) fractions. The zooplankton abundance ranged from 23 610 to 56 809 ind.m(-2) and exhibited no clear changes as a result of the SWE. In terms of abundance, calanoid copepods constituted the dominant taxa (mean: 57 %), followed by barnacle larvae (31 %). Within the calanoid copepods, small-sized Pseudocalanus spp. (65 %) and large-sized Calanus glacialis (30 %) dominated. In the population structure of C. glacialis, copepodid stage 5 (C5) dominated, and the mean copepodid stage did not vary with the SWE. The dominance of accumulated lipids in C5 and C6 females with immature gonads indicated that they were preparing for seasonal diapause. The gut pigment of C. glacialis C5 was higher at night and was correlated with ambient Chl a, and a significant increase was observed after the SWE (2.6 vs. 4.5 ng pigment ind.(-1)). The grazing impact by C. glacialis C5 was estimated to be 4.14 mgC m(-2) day(-1), which corresponded to 0.5-4.6% of the biomass of the micro-size phytoplankton. Compared with the metabolic food requirement, C. glacialis feeding on phytoplankton accounted for 12.6% of their total food requirement. These facts suggest that C. glacialis could not maintain their population by feeding solely on phytoplankton and that other food sources (i.e., microzooplankton) must be important in autumn. As observed by the increase in gut pigment, the temporal phytoplankton bloom, which is enhanced by the atmospheric turbulence (SWE) in autumn, may have a positive effect on copepod nutrition.
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  • Kohei Matsuno, Atsushi Yamaguchi, Toru Hirawake, Shigeto Nishino, Jun Inoue, Takashi Kikuchi
    POLAR BIOLOGY 38 (7) 1075 - 1079 0722-4060 2015/07 [Refereed][Not invited]
     
    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.
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  • Kaede Sato, Kohei Matsuno, Daichi Arima, Yoshiyuki Abe, Atsushi Yamaguchi
    ZOOLOGICAL STUDIES 54 (18) 1021-5506 2015/01 [Refereed][Not invited]
     
    Background: An optical plankton counter (OPC) was used to examine spatial and temporal changes in the zooplankton size spectra in the neighboring waters of Japan from May to August 2011. Results: Based on the zooplankton biovolume of equivalent spherical diameter (ESD) in 45 bins for every 0.1 mm between 0.5 and 5.0 mm, a Bray-Curtis cluster analysis classified the zooplankton communities into six groups. The geographical distribution of each group varied from each of the others. Groups with a dominance of 4 to 5 mm ESD were observed in northern marginal seas (northern Japan Sea and Okhotsk Sea), while the least biovolume with a dominance of a small-size class (0.5 to 1 mm) was observed for the Kuroshio extension. Temporal changes were observed along the 155 degrees E line, i.e., a high biovolume group dominated by 2 to 3 mm ESD during May shifted to other size spectra groups during July to August. These temporal changes were caused by the seasonal vertical descent of dominant large Neocalanus copepods during July to August. As a specific characteristic of the normalized biomass size spectra (NBSS), the slope of NBSS was moderate (-0.90) for the Neocalanus dominant spring group but was at -1.11 to -1.24 for the other groups. Theoretically, the slope of the NBSS of the stable marine ecosystem is known to settle at approximately -1. Conclusions: Based on the analysis by OPC, zooplankton size spectra in the neighboring waters of Japan were separated into six groups. Most groups had -1.11 to -1.24 NBSS slopes, which were slightly higher than the theoretical value (-1). However, one group had a moderate slope of NBSS (-0.90) caused by the dominance of large Neocalanus copepods.
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  • Atsushi Yamaguchi, Kohei Matsuno, Tomoe Homma
    ZOOLOGICAL STUDIES 54 (13) 1021-5506 2015/01 [Refereed][Not invited]
     
    Background: Despite its ecological importance, little information is available regarding the spatial and vertical changes in the calanoid copepod community over large geographical regions. This study investigated the spatial and vertical patterns in calanoid copepod abundance and community structure using zooplankton samples collected between depths of 0 and 2,615 m across the North Pacific from 0 degrees to 56 degrees N. Results: A total of 211 calanoid copepod species belonging to 66 genera and 24 families were identified. Calanoid copepod abundance decreased with increasing depth, and few latitudinal differences were detected. Across the entire region, species diversity peaked near 500 to 2,000 m in depth. The calanoid copepod community was separated into seven groups with distinct spatial and vertical distributions. For all groups, the number of species was low (28 to 37 species) in the subarctic region (north of 40 degrees N) and high (116 to 121 species) in the subtropical-tropical region. The deepest group in the subtropical-tropical region was composed of cosmopolitan species, and this group was also observed in deep water in the subarctic region. Conclusions: In deep water, most of the calanoid copepod community consisted of cosmopolitan species, while an endemic community was observed in the subarctic region. Because the food of deep-sea calanoid copepods originates from the surface layer, sufficient and excess flux in the eutrophic subarctic region may be responsible for maintaining the endemic species in the region.
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  • Atsushi Yamaguchi, Kohei Matsuno, Yoshiyuki Abe, Daichi Arima, Kohei Ohgi
    DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS 91 115 - 124 0967-0637 2014/09 [Refereed][Not invited]
     
    To identify seasonal patterns of change in zooplankton communities, an optical plankton counter (OPC) and microscopic analysis were utilised to characterise zooplankton samples collected from 0 to 150 m and 0 to 500 m in the Oyashio region every one to three months from 2002 to 2007. Based on the OPC measurements, the abundance and biomass of zooplankton peaked in June (0-150 m) or August (150-500 m), depending on the depth stratum. The peak periods of the copepod species that were dominant in terms of abundance and biomass indicated species-specific patterns. Three Neocalanus species (Neocalanus cristatus, Neocalanus flemingeri and Neocalanus plumchnis) exhibited abundance peaks that occurred before their biomass peaks, whereas Eucalanus bungii and Metridia pacifica experienced biomass peaks before their abundance peaks. The abundance peaks corresponded to the recruitment periods of early copepodid stages, whereas the biomass peaks corresponded to the periods when the dominant populations reached the late copepodid stages (C5 or C6). Because the reproduction of Neocalanus spp. occurred in the deep layer ( > 500 m), their biomass peaks were observed when the major populations reached stage C5 after the abundance peaks of the early copepodid stages. The reproduction of E. bungii and M. paafica occurred near the surface layer. These species first formed biomass peaks of C6 and later developed abundance peaks of newly recruited early copepodid stages. From the comparison between OPC measurements and microscopic analyses, seasonal changes in zooplankton biomass at depths of 0-150 m were governed primarily by E. bungii and M. pacifica, whereas those at depths of 150-500 m were primarily caused by the three Neocalanus species. (C) 2014 Elsevier Ltd. All rights reserved.
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  • Kohei Matsuno, Mutsuo Ichinomiya, Atsushi Yamaguchi, Ichiro Imai, Takashi Kikuchi
    POLAR BIOLOGY 37 (8) 1185 - 1195 0722-4060 2014/08 [Refereed][Not invited]
     
    The western Arctic Ocean is composed of two regions: the southern shelf and the northern basin, whereas the marine ecosystem structure is expected to vary between the regions, little information is available, particularly for the planktonic protist community. In this study, we surveyed the horizontal distribution of microprotists (diatoms, dinoflagellates and ciliates) at 59 stations in the western Arctic Ocean during September and October of 2010. The abundances of diatoms, dinoflagellates and ciliates were 0-138,640, 0-16,460 and 0-10,933 cells L-1, respectively, and all of the abundances were higher on the Chukchi Sea shelf. Cluster analysis based on abundance separated the microprotist community into five groups, which contain 25, 22, 6, 4 and 2 stations. The largest group was observed on the Chukchi Sea shelf, showing a high abundance predominated by diatoms (78 % of total abundance). The second group was observed from the East Siberian Sea to the Canada Basin, characterised by low abundance and ciliate dominance (36 % of total abundance). Because of the high abundance and predominance of diatoms, the former group is characterised by eutrophic waters, which are enhanced by the continuous inflow of the nutrient-rich Pacific Water through the Bering Strait. Due to the low abundance and the dominance of ciliates, the latter group is dominated by organisms of the microbial food web. The remaining three groups were smaller and located between the two large groups. The distribution of these three groups may be based on complex physical structures, such as the anticyclonic eddy near the shelf break.
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  • Eiji Watanabe, Jonaotaro Onodera, Naomi Harada, Makio C. Honda, Katsunori Kimoto, Takashi Kikuchi, Shigeto Nishino, Kohei Matsuno, Atsushi Yamaguchi, Akio Ishida, Michio J. Kishi
    NATURE COMMUNICATIONS 5 doi: 10.1038/ncomms4950  2041-1723 2014/05 [Refereed][Not invited]
     
    The future conditions of Arctic sea ice and marine ecosystems are of interest not only to climate scientists, but also to economic and governmental bodies. However, the lack of widespread, year-long biogeochemical observations remains an obstacle to understanding the complicated variability of the Arctic marine biological pump. Here we show an early winter maximum of sinking biogenic flux in the western Arctic Ocean and illustrate the importance of shelf-break eddies to biological pumping from wide shelves to adjacent deep basins using a combination of year-long mooring observations and three-dimensional numerical modelling. The sinking flux trapped in the present study included considerable fresh organic material with soft tissues and was an order of magnitude larger than previous estimates. We predict that further reductions in sea ice will promote the entry of Pacific-origin biological species into the Arctic basin and accelerate biogeochemical cycles connecting the Arctic and subarctic oceans.
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  • Kohei Matsuno, Atsushi Yamaguchi, Amane Fujiwara, Jonaotaro Onodera, Eiji Watanabe, Ichiro Imai, Sanae Chiba, Naomi Harada, Takashi Kikuchi
    JOURNAL OF PLANKTON RESEARCH 36 (2) 490 - 502 0142-7873 2014/03 [Refereed][Not invited]
     
    To examine seasonal changes in the mesozooplankton community, analyses were made on the swimmer samples (>1 mm) collected by a sediment trap mooring at 184 m depth on the Northwind Abyssal Plain in the western Arctic Ocean during October 2010-September 2011. The zooplankton swimmer flux ranged from 5 to 44 ind. m(-2) day(-1) and was greater during July to October; copepods were the dominant taxon. Based on the zooplankton swimmer flux, cluster analysis classified samples into three groups (A, B-1 and B-2). The occurrence of each group showed clear seasonality; group A was observed during July to October, group B-1 was seen in November to January and group B-2 during March to June. The seasonal variability in population structures of four dominant copepod swimmers was clearly different between the species. Most Calanus hyperboreus were copepodid stage 6 female (C6F) throughout the year. For Metridia longa and Paraeuchaeta glacialis, C6Fs dominated during January to May, and early copepodid stages increased during June to October. Heterorhabdus norvegicus was dominated by stage C5 during November to February, and C6F/M during March to May. Since Pacific copepods (Neocalanus cristatus) occurred in significant number during August-September, possible causes are discussed.
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  • Daichi Arima, Atsushi Yamaguchi, Yoshiyuki Abe, Kohei Matsuno, Rui Saito, Hiroki Asami, Hiroshi Shimada, Ichiro Imai
    CRUSTACEANA 87 (3) 364 - 375 0011-216X 2014/03 [Refereed][Not invited]
     
    Seasonal changes in body size (prosome length: PL) and oil sac volume (OSV) of the three most numerically abundant copepods in Ishikari Bay, northern Sea of Japan, Paracalanus parvus (Claus, 1863), Pseudocalanus newmani Frost, 1989 and Oithona similis Claus, 1866, were studied using monthly samples collected through vertical hauls of a 100-mu m mesh NORPAC net from March, 2001 to May, 2002. Seasonal changes in PL were common for the three species and were more pronounced during a cold spring. PL was negatively correlated with temperature, and this relationship was described well using the Belehradek equation. Seasonal changes in OSV exhibited a species-specific pattern, i.e., OSV was greater during a warm summer for P. parvus and was greater during a cold spring for P. newmani and O. similis. The OSV peak period corresponded with the optimal thermal season of each species. The relative OSV to prosome volume of the small copepods (0.6-0.8%) was substantially lower than that of the large copepods (20-32%). These facts suggest that the oil sac of small copepods is not used for overwintering or diapauses or during periods of food scarcity, but is instead used as the primary energy source for reproduction, which occurs during the optimum thermal season of each species.
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  • Yoshiyuki Abe, Masafumi Natsuike, Kohei Matsuno, Takeshi Terui, Atsushi Yamaguchi, Ichiro Imai
    JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 449 321 - 329 0022-0981 2013/11 [Refereed][Not invited]
     
    The assimilation efficiency of zooplankton is an essential parameter required to estimate energy transfer to higher trophic levels in marine ecosystems. However, little information is available for large oceanic copepods, especially the Neocalanus and Eucalanus species dominant in the subarctic Pacific. In this study, the assimilation efficiencies of the C5 stages of Neocalanus cristatus, Neocalanus flemingeri and Eucalanus bungii were evaluated using eight phytoplankton species as food. The average assimilation efficiencies of N. cristatus, N. flemingeri and E. bungii ranged between 45 and 66%, 44 and 66% and 34 and 65%, respectively. The assimilation efficiency was highly variable depending on the food phytoplankton species. In all species, the assimilation efficiency showed a significant negative relationship with the ash content of the phytoplankton (r(2) = 0.79-0.87, p<0.001). The assimilation efficiency of large-body sized N. cristatus for large-sized diatoms was higher than for the other copepod species. In population models of N. cristatus, changes in assimilation efficiency affect the growth and survival rates of the population. The Lagrangian ensemble model (LEM) for N. cristatus showed that, for assimilation efficiencies less than 57%, the population could not be maintained. Because variations in assimilation efficiency may have significant effects on the copepod population, their variability should be incorporated into marine ecosystem models in the future. (C) 2013 Elsevier B.V. All rights reserved.
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  • Chiko Tsukazaki, Ken-Ichiro Ishii, Rui Saito, Kohei Matsuno, Atsushi Yamaguchi, Ichiro Imai
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 94 22 - 30 0967-0645 2013/10 [Refereed][Not invited]
     
    Information on diatom resting stages is fundamentally important to understanding the population dynamics of diatoms including bloom formation. The distribution of viable diatom resting stage cells in bottom sediments of the eastern Bering Sea in July 2009 was investigated by the most probable number (MPN) method. The abundances of diatom resting stage cells ranged from 1.7 x 10(3) to 1.2 x 10(6) MPN cells cm(-3) wet sediment, comparable to those in shallow eutrophic areas where diatom blooms frequently occur. Common species during the spring phytoplankton bloom in the eastern Bering Sea were also dominant in sediments as resting stage cells. It should be noted that relatively high numbers of ice algae species, especially ribbon-shaped chain forming pennate diatoms, were found in the sediments. The life cycle strategy using resting stage cells allows planktonic and ice algal species to survive unfavorable environmental conditions such as the dark winter season, and potentially contribute to form blooms of several types (subsurface of ice, ice edge, plankton) through vertical mixing. (C) 2013 Elsevier Ltd. All rights reserved.
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  • Rie Ohashi, Atsushi Yamaguchi, Kohei Matsuno, Rui Saito, Nao Yamada, Anai Iijima, Naonobu Shiga, Ichiro Imai
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 94 44 - 56 0967-0645 2013/10 [Refereed][Not invited]
     
    On the southeastern Bering Sea shelf, mesozooplankton plays an important role in material transfer between primary producers and fisheries resources. The biomass of mesozooplankton in this region is known to vary annually, but little is known about annual changes in community structure and species composition. In the present study, regional and long-term changes in abundance, biomass and community structure of copepods and chaetognaths on the shelf were evaluated based on NORPAC net samples collected during summers of 1994-2009. During the study period, regime shifts occurred from high interannual variability regime (1994-1999) to low interannual variability regime with high temperature (2000-2005), then to a low interannual variability regime with low temperature (2007-2009). A total of 24 calanoid copepod species belonging to 21 genera were identified from samples. Copepod abundance ranged from 150 to 834,486 inds. m(-2), was greatest on the Middle shelf, and was higher in cold years, than in warm years. Copepod biomass ranged from 0.013 to 150 g DM m(-2), and was also higher in cold years than in warm years. Based on the results of cluster analysis, the copepod community was divided into six groups (A-F). The regional and interannual distributions of each group were distinct. Interannual changes in abundance of the dominant copepod on the Outer shelf and Middle shelf were highly significant (p < 0.0001), and their abundances were negatively correlated with temperature and salinity. Interannual changes in copepod community that occurred between cold and warm years are thought to have been caused by differences in the magnitude and timing of the spring phytoplankton bloom between the two regimes. Abundance and biomass of the chaetognath Parasagitta elegans ranged from 30 to 15,180 inds. m(-2) and from 11 to 1559 mg DM m(-2), respectively. Chaetognath abundance was significantly correlated with the abundance of the dominant copepods (p < 0.0001). Differences in cold and warm years may also affect recruitment of walleye pollock. We conclude that on the southeastern Bering Sea shelf, the magnitude and timing of primary production, which is related to climate change, may significantly affect how it is transferred through the food web. (C) 2013 Elsevier Ltd. All rights reserved.
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  • Atsushi Yamaguchi, Tomoe Homma, Rui Saito, Kohei Matsuno, Hiromichi Ueno, Toru Hirawake, Ichiro Imai
    Plankton and Benthos Research 8 (3) 116 - 123 1882-627X 2013/08 [Refereed][Not invited]
     
    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.
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  • Masafumi Natsuike, Satoshi Nagai, Kohei Matsuno, Rui Saito, Chiko Tsukazaki, Atsushi Yamaguchi, Ichiro Imai
    HARMFUL ALGAE 27 52 - 59 1568-9883 2013/07 [Refereed][Not invited]
     
    Abundance and distribution of the toxic dinoflagellate Alexandrium tamarense species complex resting cyst were investigated in the eastern Bering Sea and the Chukchi Sea for the first time. Sediment samples (top 0-3 cm depth) were collected from the continental shelf of the eastern Bering Sea (17 stations) and the Chukchi Sea (13 stations) together with a long core sample (top 0-21 cm depth) from one station in the Chukchi Sea during 2009-2012. The cysts were enumerated using the primuline staining method. Species identification of the cysts was carried out with multiplex PCR assay and the plate morphology of vegetative cells germinated from cysts in the both areas. Alexandrium cysts were widely detected in the both areas, ranging from not detected (<1 cysts cm(-3)) to 835 cysts cm(-3) wet sediment in the eastern Bering Sea and from not detected (<1 cysts cm(-3)) to 10,600 cysts cm(-3) in the Chukchi Sea, and all isolated cysts were genetically and morphologically identified as the North American clade A. tamarense. Their cysts were mainly distributed in the shallow continental shelf where the water depth was less than 100 m in both areas. The cysts were detected from the deep layer (18-21 cm depth of sediment core) of the long core sample. The present study confirmed the abundant existence of A. tamarense with wide range of distribution in these areas. This fact suggests that A. tamarense vegetative cells have appeared in the water column in the both areas. Furthermore, these abundant cyst depositions indicate that this species originally distributed in the Arctic and subarctic regions and well adapted to the environments in the marginal ice zone. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.
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  • Kana Chikugo, Atsushi Yamaguchi, Kohei Matsuno, Rui Saito, Ichiro Imai
    CRUSTACEANA 86 (4) 449 - 474 0011-216X 2013/04 [Refereed][Not invited]
     
    Pelagic Mysidacea and Decapoda have important roles in marine ecosystems. However, information on their life histories is extremely limited. This study aimed to evaluate the life cycles of pelagic Mysidacea and Decapoda in the Oyashio region, Japan. Production of the four dominant species was estimated by combining body mass (DM) data and abundance data Mysidacea belonging to 5 species from 5 genera occurred in the study area. Their abundance and biomass ranged between 11.7-50.1 ind. m(-2) and 1.2-7.9 g wet mass (VIM) m(-2), respectively. Six species from 6 genera belonged to Decapoda, and their abundance and biomass ranged between 9.0-17.3 ind. M-2 and 3.0-17.3 g WM M-2, respectively. Based on body length histograms, there were two to four cohorts for the three dominant mysids and one dominant decapod on each sampling date. Life histories of the two numerically dominant mysids (Eucopia australis and Boreomysis californica) followed similar patterns: recruitment of young in May, strong growth from April to June, and a longevity of three years. Life cycles of the two minor species (the mysid Meterythrops microphthalma and the decapod Hymenodora frontalis) were not clear because of their low abundance. The timing of recruitment of the young and the strong juvenile growth for the two dominant mysids corresponds with the season when their prey is abundant. The annual production of the dominant mysid species was 14.0 mg DM M-2 (B. californica) and 191.8 mg DM m(-2) (E. australis). Annual production/biomass (P / B) ratios ranged between 0.242 (H. frontalis) and 0.643 (M. microphthalma). Compared with other regions, the Oyashio region showed high production and low P / B ratios. The high production in the Oyashio region may be related to the high biomass of these species. Because of the low temperature conditions (3 degrees C), pelagic mysids and decapods in the Oyashio region may have slower growth, longer generation times and lower P / B ratios than in other oceans.
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  • Kohei Matsuno, Atsushi Yamaguchi, Ichiro Imai
    ICES JOURNAL OF MARINE SCIENCE 69 (7) 1205 - 1217 1054-3139 2012/09 [Refereed][Not invited]
     
    An optical plankton counter was used to examine the regional characteristics of the zooplankton communities in the Chukchi Sea during the summers of 1991, 1992, 2007, and 2008. Zooplankton abundance and biomass ranged from 5000 to 1 170 000 ind. m(-2) and 0.2 to 10.9 g dry mass m(-2), respectively. Based on zooplankton biovolume in equivalent spherical diameter (ESD) in 48 bins, one every 0.1 mm between 0.25 and 5.0 mm, a Bray-Curtis cluster analysis classified zooplankton communities into four groups (A-D). No changes were observed in zooplankton communities south of the Lisburne Peninsula (group A) throughout the 4 years, but there were differences north of the Peninsula, with group B (normal, intermediate biomass) observed in 1991/1992, group D (low biomass) in 2007, and group C (predominance of barnacle larvae) in 2008. Analysis of the normalized biomass size spectra for the groups indicated that groups A and C were very productive, so the zooplankton community south of the Lisburne Peninsula was consistently highly productive, which may be because of the continuous inflow of Pacific Water rich in nutrients. Zooplankton communities north of the Lisburne Peninsula varied greatly from year to year, which may be related to interannual changes in sea-ice extent.
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  • Kohei Matsuno, Atsushi Yamaguchi, Koji Shimada, Ichiro Imai
    POLAR SCIENCE 6 (1) 105 - 119 1873-9652 2012/04 [Refereed][Not invited]
     
    The horizontal distribution of the epipelagic zooplankton communities in the western Arctic Ocean was studied during August October 2008. Zooplankton abundance and biomass were higher in the Chukchi Sea, and ranged from 3,000 to 274,000 ind. m(-2) and 5-678 g WM m(-2), respectively. Copepods were the most dominant taxa and comprised 37-94% of zooplankton abundance. For calanoid copepods, 30 species belonging to 20 genera were identified. Based on the copepod abundance, their communities were classified into three groups using a cluster analysis. The horizontal distribution of each group was well synchronized with depth zones, defined here as Shelf, Slope and Basin. Neritic Pacific copepods were the dominant species in the Shelf zone. Arctic copepods were substantially greater in the Slope zone than the other regions. Mesopelagic copepods were greater in the Basin zone than the other regions. Stage compositions of large-sized Arctic copepods (Calanus glacialis and Metridia longa) were characterized by the dominance of late copepodid stages in the Basin. Both the abundance and stage compositions of large copepods corresponded well with Chl. a concentrations in each region, with high Chl. a in the Shelf and Slope supporting reproduction of copepods resulting in high abundance dominated by early copepodid stages. (C) 2012 Elsevier B.V. and NIPR. All rights reserved.
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  • Jumpei Fukuda, Atsushi Yamaguchi, Kohei Matsuno, Ichiro Imai
    Plankton and Benthos Research 7 (2) 64 - 74 1882-627x 2012 [Refereed][Not invited]
     
    To evaluate zooplankton interannual and latitudinal changes, Optical Plankton Counter analyses were made on preserved net zooplankton samples collected by NORPAC net from 0-150 m at 35°N-51°N stations along 180° in the central North Pacific during early-mid June 1981-2000. The mean numerical abundance of total zooplankton for the 20 years varied latitudinally from 19,200 to 84,300 ind. m-2but the differences between the three oceanic domains were not significant. However, highly significant latitudinal changes were observed in the mean zooplankton biomass, which ranged from 1.44 to 13.2 mg dry mass m-2with higher values in the Transitional Domain (TR) than in the Subarctic and Subtropical Domains. The high biomass in the TR was caused by the dominance of large-sized zooplankton with equivalent spherical diameters (ESD) of 2-4 mm, regarded to consist mainly of Neocalanus spp. C5. Both the slope and intercept of the Normalized Biomass Size Spectrum also showed significant latitudinal changes with a moderate slope and low intercept in the TR due to the dominance of large zooplankton with 2-4 mm ESD in biomass. In contrast to these large latitudinal changes, only limited interannual variations were observed for zooplankton abundance and biomass in the central North Pacific during the study period. © 2012, The Plankton Society of Japan, The Japanese Association of Benthology. All rights reserved.
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  • Kohei Matsuno, Atsushi Yamaguchi, Toru Hirawake, Ichiro Imai
    POLAR BIOLOGY 34 (9) 1349 - 1360 0722-4060 2011/09 [Refereed][Not invited]
     
    A recent drastic decrease in sea ice cover area was observed in the western Arctic Ocean during summer, yet little information is available for its effect on zooplankton community. To evaluate the effect of sea ice reduction on zooplankton, we studied year-to-year changes of zooplankton community structure in the Chukchi Sea during summers of 1991, 1992 (when sea ice extended), 2007, and 2008 (when sea ice reduced). Zooplankton abundance ranged from 4,000 to 316,000 ind. m(-2) (mean: 70,000) and was greater north of Lisburne Peninsula in 2008. Zooplankton biomass ranged from 0.07 to 286 g wet mass m(-2) (mean: 36) and was greater south of Lisburne Peninsula in 2007. Cluster analysis based on zooplankton abundance showed a division of the zooplankton community into four groups. Occurrence of each group was separated geographically and interannually, and geographic distributions of each group in 1991 and 1992 were similar but those in 2007 and 2008 were shifted northward. Abundance and biomass in 2007/2008 were higher than in 1991/1992, indicating that further sea ice reduction would have a positive effect on zooplankton production (e.g. invasion of large Pacific species and temperature effects on their growth rate). The northern shift in geographic distribution of the zooplankton community in 2007/2008 indicates that sea ice reduction would have a negative effect on the zooplankton community (loss of characteristic Arctic species) in part of the Chukchi Sea. These apparently contradictory effects of sea ice reduction on zooplankton community emphasize the critical need for continued monitoring in this area.
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  • Kohei Matsuno, Atsushi Yamaguchi
    Plankton and Benthos Research 5 (4) 123 - 130 1880-8247 2010 [Refereed][Not invited]
     
    Zooplankton abundance and biomass along 165°E and 165°W in the North Pacific were estimated using an optical plankton counter on preserved samples collected with a plankton net of 335μ m mesh-size from 0-150 m at 89 stations from the subarctic to subtropical regions during the summers of 2003-2006 the stations were grouped into subarctic (SA), transitional (TR) and subtropical (ST) regions for latitudinal comparisons. The two-way ANOVA and a post hoc test showed that total abundance and biomass were significantly larger in SA and smaller in ST stations, respectively, than in the other regions, but were not significantly different between 165°E and 165°W. Total ranges of abundance and biomass were: 34×103-65×103 indiv. m-2 and 2.9-7.9 g dry mass m-2, respectively. The variation in abundance was mainly governed by the variation of 0.34-1.00 mm equivalent spherical diameter (ESD) size class zooplankton, but total biomass variations were due mainly to the 2.00-3.00 mm ESD size class, which corresponds to the calanoid copepod Neocalanus spp. copepodid stage 5 (C5) that had a greater abundance in SA and TR than in ST. Despite possibly higher abundances of Neocalanus C5 in TR than in SA, abundance and biomass of the 2.00-3.00mm ESD size class were not significantly different between the two regions. Size reduction of individuals due to higher temperatures in TR than in SA may be a possible explanation. © The Plankton Society of Japan.
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  • Kohei Matsuno, Hye Seon Kim, Atsushi Yamaguchi
    Plankton and Benthos Research 4 (4) 154 - 159 1882-627x 2009 [Refereed][Not invited]
     
    Size-fractionated (0.25, 0.5, 1, 2, and 4 mm mesh size) wet mass (WM) and dry mass (DM) determinations and optical plankton counter (OPC) measurements were carried out on zooplankton samples collected at 15 stations in the northern North Pacific Ocean, Bering Sea and Chukchi Sea during July-August 2007. The total sampleWM and DM estimated from OPC data corresponded closely to those of measured values by a factor of 0.970-1.098. However when the sample was portioned into different size groups, estimates of size-fractionated WM and DM by OPC data varied from measured masses by a factor of between 0.202 and 1.768. The high variability was caused by an underestimation of sizes of the large sized (< mm) fraction, or an overestimation of the number of the small size fraction (2-4 mm). The underestimation in the < mm and overestimation in the 2-4 mm respectively were caused by the dominance of transparent hydromedusae, and slender-shaped euphausiids in the < mm fraction. This study suggests that OPC analysis could be susceptible to errors in zooplankton biomass estimates in the large size fraction (< mm) especially when euphausiids and hydromedusae dominate the population. On the other hand, OPC based estimates of DM within 0.25-4 mm size fraction are more robust, which may be due to the dominance of large copepods, and low detritus content in the samples from the oceanic subarctic Pacific, in summer 2007. © 2009, The Plankton Society of Japan, The Japanese Association of Benthology. All rights reserved.
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MISC

Books etc

  • プランクトンは海の語り部 ~変わりゆく極域~
    松野孝平 (Single work)
    海文堂出版 2020/09
  • 水産科学・海洋環境科学実習
    山口 篤, 今井一郎, 平譯 享, 松野孝平 (Joint work)
    海文堂出版 2019/08
  • 海をまるごとサイエンス ～水産科学の世界へようこそ～
    松野孝平 (Contributor小さな生き物から地球を知る)
    海文堂出版 2018/08
  • 低温環境の科学辞典
    松野孝平 (Contributor北極の動物プランクトン)
    朝倉書店 2016/07

Association Memberships

  • JAPAN GEOSCIENCE UNION   Association for the Sciences of Limnology and Oceanography   THE OCEANOGRAPHIC SOCIETY OF JAPAN   THE PLANKTON SOCIETY OF JAPAN   日本水産学会   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2022/04 -2027/03 
    Author : 山口 篤, 松野 孝平
  • 日本学術振興会：科学研究費助成事業 基盤研究(B)
    Date (from‐to) : 2021/04 -2026/03 
    Author : 松野 孝平
     
    本研究は、海氷衰退が著しい北極海陸棚域において、海氷下と海底面での珪藻類による一次生産量と種組成を明らかにし、海氷分布と比較することで、海氷変動による珪藻類生産への影響を解明することを目的としている。令和3年度（2021年度）は、JAMSTEC海洋地球研究船みらいの北極航海（2021年8月28日～10月22日）に参加し、太平洋側北極海において海氷試料（4地点）、海水試料（45地点）および海底堆積物（11地点）を採取した。また、船上において、本研究課題の予算で購入したPAM（パルス変調蛍光光度計）を用いた光合成パラメーターの測定（175回）、およびviability染色キットによる生死判別試料の作成も行った。2021年度の太平洋側北極海は、例年よりも海氷が多く残っていたために、海氷のサンプリングができたことが大きな成果である。これにより、同一地点において、海氷、海表面の海水、亜表層クロロフィルa最大層の海水、海底直上10 mの海水、海底堆積物の直上水および海底堆積物を採取し、かつPAMによる光合成活性の測定と生死判別分析もできているため、本研究課題の核をなす結果が得られると期待できる。本研究に関連する研究成果としては、査読付き論文4報、学会での口頭及びポスター発表を6件行った。 令和3年度において、最も重要な研究成果としては、太平洋側北極海の海底堆積物中の珪藻類の休眠期細胞の分布と組成は、海氷の融解時期や分布に大きく影響を受けていることを明らかにした点である。これにより、本研究課題で設定した仮説「海氷変動が珪藻類の休眠期細胞に影響を与えること」が実証された。この研究では、アイスアルジーの存在割合が、結氷期間が長い海域ほど高くなることも示している。この成果は、本研究で取り組むバイオマーカー（つまり、アイスアルジー）の分布も、海氷と密接に関係していることを示唆している。
  • 氷河がフィヨルド環境に果たす役割 ―グリーンランドとパタゴニアで何が違うのか―
    北海道大学低温科学研究所：
    Date (from‐to) : 2024/04 -2025/03 
    Author : 野村大樹, 杉山慎, 漢那直也, 松野孝平, 干場康博
  • 海洋課題 北極海環境動態の解明と汎用データセットの構築
    文部科学省 北極域研究加速プロジェクト：
    Date (from‐to) : 2022/04 -2025/03 
    Author : 渡邉 英嗣, 上野 洋路, 伊東 素代, 木村 仁, 張 圓昕, 安中 さやか, 八田 真理子, 中嶋 亮太, 池上 隆仁, 村田 昌彦, 重光 雅仁, 野口 真希, 西野 茂人, 小野寺丈尚太郎, 藤原 周, 杉江 恒二, 木元 克典, 喜多村 稔, 阿部 泰人, 松野 孝平, 笠井 亮秀, 川上 達也, 野村 大樹, 平田 貴文, ガルシア・モリノス・ホルヘ, アラビア・ドロルフイー・アイリーン, 大島 慶一郎, 西岡 純, 亀山 宗彦, 山本 正伸, 平譯 享, 伊藤 優人, 原田 尚美, 塩崎 拓平, 川口 悠介, 小平 翼, 溝端 浩平, 川合 美千代
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2021/04 -2025/03 
    Author : 藤原 周, 八田 真理子, 伊藤 優人, 塩崎 拓平, 松野 孝平
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2017/04 -2022/03 
    Author : Yamaguchi Atsushi
     
    To evaluate the effects of climate changes on the marine lower trophic level ecosystems, I analyzed wet weight biomass of the formalin-preserved zooplankton samples collected by the same method in the southeastern Bering Sea shelf during the summers of 1955 to 2013. Size and taxonomic accounts of the samples for the consecutive two years belonging to the four different climate regimes were also analyzed by the imaging device: ZooScan. For the field imaging analyzing devices, I developed the frame-mounted camera for quantification of the macro-sized gelatinous zooplankton (jellyfish). In 2017 and 2018, when the timing of the sea ice melting was greatly different, I analyzed the abundance and biomass of each trophic level from phytoplankton to seabirds, and evaluated the relationship between environmental variables and biomasses at each trophic level.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/04 -2021/03 
    Author : MATSUNO Kohei
     
    Copepods quickly increased their grazing rate in autumn phytoplankton bloom of the Arctic Ocean. While, Pacific copepods did not actively graze the phytoplankton in the Arctic Ocean. These grazing activities were controlled by not only exogenous factors (food contents) but also endogenous factors (lipid accumulation). Their reproduction was governed with the timing of spring phytoplankton bloom associated with sea-ice melt.
  • Hokkaido University：Researcher’s Community Support Projects Promoting collaborative research
    Date (from‐to) : 2019/04 -2020/03 
    Author : Matsuno Kohei
  • 公益財団法人水産無脊椎動物研究所：2019年度個別研究助成
    Date (from‐to) : 2019/04 -2020/03 
    Author : 松野孝平
  • 季節海氷域における海氷期の生態系構造に関する研究
    Hokkaido University：Researcher’s Community Support Projects Promoting collaborative research
    Date (from‐to) : 2018/04 -2019/03 
    Author : Matsuno Kohei
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2015/04 -2019/03 
    Author : ONODERA Jonaotaro
     
    We studied relationship between physical oceanographic condition (dynamics of sea-surface current system and oceanic eddies) and transportation of shelf materials (such as plankton remains and lithogenic matters) to basin in Pacific side of the Arctic Ocean (western Canada Basin and Chukchi Borderland) where recent sea-ice reduction is remarkable. Annual and interannual fixed-point observation using sediment trap mooring showed that supply of shelf-origin particles increased when lateral advection of Pacific-origin water and oceanic eddies containing shelf matters reached to the monitoring stations. It was suggested that large interannual differences on physical oceanographic dynamics for 2011-2018 changed the distribution of laterally transported shelf-origin matters in offshore side of study region. It is suggested that those hydrographic changes influence to lower-trophic ecosystems applying shelf-origin matters in the basin side.
  • Japan Society for the Promotion of Science：
    Date (from‐to) : 2016/04 -2018/03 
    Author : Matsuno Kohei
  • Early Career Scientist Fellowships for Arctic Environmental Research
    National Institute of Polar Research：
    Date (from‐to) : 2014/12 -2014/12 
    Author : Matsuno Kohei
  • Support for traveling abroad
    Japan Marine Science Foundation：
    Date (from‐to) : 2012/02 -2012/02 
    Author : Kohei Matsuno
  • 日本学術振興会：科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 2011 -2012 
    Author : 松野 孝平
     
    本研究は研究サブテーマとして以下の4つを設け、本年度より派生展開的な新サブテーマ(5)を設けた。以下に各サブタイトルの成果を記す。 (1)2010年夏季の西部北極海における植物プランクトンの水平分布 2010年みらい北極航海にて採取した植物プランクトン試料を解析した。得られた結果をまとめ、IPY2012にてポスター発表を行った。さらに、「Horizontal distribution of microplankton community structure in the western Arctic Ocean during late summer of 2010」とした学術論文をPolar Biologyに投稿し、現在査読中である。 (2)2010年夏季の西部北極海における動物プランクトンの水平分布 2008および2010年みらい北極航海にて採集した動物プランクトン試料の検鏡を行った。得られた結果をまとめ、ASLOにて口頭発表を行った。今後は、2012年みらい航海の試料も解析する予定である。 (3)西部北極海における動物プランクトンの摂餌生態 2010年および2012年のみらい北極航海においてカイアシ類摂餌実験(計18回)によりデータを取得した。しかし、取得したデータだけでは「動物プランクトンによる植物プランクトンへの摂餌インパクトの評価」には不十分であるため、2013年6-7月のおしょろ丸北洋航海および9-10月のみらい北極航海にて引き続き実験を行う予定である。 (4)チャクチ海における動物プランクトンサイズ組成の経年変動 1991、1992、2007および2008年にチャクチ海で採集された動物プランクトン試料のOPC測定を行った。得られた結果をまとめ、タイトル「Biomass size spectra of mesozooplankton in the Chukchi Sea during summers of 1991/1992 and 2007/2008:an analysis by optical plankton counter」とした学術論文を執筆し、2nd ESSASの特集号(ICES Journal of Marine Science)に学術論文を投稿し、受理・印刷済みである。 (5)セジメントトラップによって採集された動物プランクトン群集の季節変動 西部北極海において2010年10月～2011年9月にかけてセジメントトラップにより採集された動物プランクトン試料の解析を行った。得られた結果を、3rd ESSASおよびISAR-3にて発表し、タイトル「Seasonal changes in mesozooplankton swimmers collected by sediment trap moored in the western Arctic Ocean」とした学術論文をJournal of Plankton Researchに投稿し、現在査読中である。

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