研究者詳細 - 小針　統

論文 - 小針　統

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Kobari T., Manako Y., Hara A., Yamanoue K., Azuma T., Fukuda R., Wang Y.C., Kodama M., Kume G. . Community structure of fish larvae associated with advections of the Kuroshio and its neighboring waters . Progress in Oceanography231 103386 - 103386 2025年2月査読

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress in Oceanography

The Kuroshio has been long thought to be disadvantageous as nursery grounds for larval fishes due to the low plankton standing stocks under the oligotrophic conditions. Despite of the potential risk for survival and growth, early life stages of various fishes appear abundantly in the Kuroshio and its neighboring waters. Here, we report what kind of taxonomic groups establish community structure of larval fishes in the Continental shelf waters (CW) and the Kuroshio (KW). 16 orders and 78 families were classified in the present study. Mesopelagic fishes more abundantly appeared in the KW than in the CW, while larval fish abundance was not different between the two areas. Multivariate analysis demonstrated the regional difference of the taxonomic compositions, represented by Callionymidae, Bothidae, Labridae and Bregmacerotidae for the CW and Gonostomatidae, Myctophidae and Notosudidae for the KW. Abundance of fish larvae to ambient salinity exhibited significantly positive correlations for Gonostomatidae, Sigmops gracilis and Myctophum orientale predominated in the KW and negative correlations for Labridae appeared abundantly in the CW. These results suggest that mixture of advected specimens from the coastal and Kuroshio waters also contribute to larval fish community with high biodiversity and comparable abundance between the Kuroshio and its neighboring waters.

DOI： 10.1016/j.pocean.2024.103386

Scopus

Kume G., Oba H., Kodama M., Shigemura T., Shiozaki K., Ichinomiya M., Komorita T., Azuma T., Kobari T. . Growth, mortality, and predatory impact on mesozooplankton of chub mackerel Scomber japonicus larvae in an upwelling system, southern Japan . Continental Shelf Research285 105399 - 105399 2025年2月査読

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Continental Shelf Research

In the northern Satsunan area, southern Japan, upwellings generated by the intrusion of the Kuroshio branch current into Kagoshima Bay are observed at the bay's mouth once every two weeks in winter and spring, and the resulting nutrient supply promotes phytoplankton blooms. Currently, this is a key spawning and nursery habitat for chub mackerel Scomber japonicus in Japan. This study examined how water temperature and prey density influenced the growth, mortality, and predatory effects of S. japonicus larvae in the northern Satsunan area. Recent growth (measured as the average width of the last three otolith increments) of S. japonicus larvae was positively correlated with water temperature but not with prey density, indicating that prey abundance was adequate for larvae and that water temperature controlled their growth rate in the study area. The instantaneous daily mortality rate of S. japonicus larvae was 0.322 in 2021 and 0.252 in 2022 (equivalent to 27.5% mortality d−1 in 2021 and 22.3% in 2022). The food requirements of S. japonicus larvae and mesozooplankton production were 0.00427 ± 0.00334 and 6.37 ± 3.04 mg DW m−3 d−1, respectively. S. japonicus larvae had no significant predatory impact on mesozooplankton (0.0869 ± 0.0796%). The present study suggests that none of the plankton feeders have a significant top-down regulating effect on mesozooplankton biomass in the northern Satsunan area, which provides a good food environment for S. japonicus larvae.

DOI： 10.1016/j.csr.2024.105399

Scopus

Kodama M., Yamazaki R., Hayakawa J., Murata G., Tomikawa K., Kawamura T., Kume G., Kobari T. . Feeding ecology of the urchin symbiont Dactylopleustes yoshimurai (Amphipoda) revealed by DNA metabarcoding . Marine Biology171 ( 10 ) 2024年10月

担当区分：最終著者記述言語：日本語出版者・発行元：Marine Biology

The nature of symbiotic relationships between organisms can be difficult to assess and may range from commensalism, to mutualism, and parasitism. Trophic linkage and feeding ecology are essential to disentangle symbiont-host relationships/interactions. Amphipods of the genus Dactylopleustes are known as urchin symbionts. Though their ecology remains largely unknown, Dactylopleustes was recently reported to aggregate on diseased hosts, suggesting that Dactylopleustes feeds on diseased urchins’ tissues and uses urchins as both a habitat and prey. We investigated by DNA metabarcoding analyses, the feeding ecology of Dactylopleustes yoshimurai in relation to growth and disease status of the host (Strongylocentrotus intermedius). Contrary to our hypothesis, sequence reads from the gut contents were dominated by planktonic copepods regardless of body size or host disease status. These results suggest that they mainly feed on copepod fecal pellets deposited on sediments, and do not have a strong trophic linkage with their host. Large individuals on diseased urchins feed more on urchins than those on healthy urchins. However, their main prey still remains copepods, implying that host disease has a limited effect on the feeding behavior. In conclusion, our study indicates that this species is mainly commensal, but also may parasitize its host depending on the situation.

DOI： 10.1007/s00227-024-04507-1

Scopus

Kobari T., Taniguchi A., Hirata M., Kume G., Ichinomiya M., Komorita T., Kodama M., Makino F., Hirai J. . Comparison of the trophic sources and pathways of mesozooplankton and ichthyoplankton in the Kuroshio current and its neighboring waters . Progress in Oceanography229 103356 - 103356 2024年9月査読

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress in Oceanography

Commercially important fish spend their vulnerable early life stages in the Kuroshio Current, resulting in high fishery production even in the vicinity of poor prey availability under oligotrophic conditions. Nevertheless, little information is available on how ichthyoplankton are supported by trophodynamics in complicated food webs. Here, we have explored trophic sources and pathways toward ichthyoplankton in the Kuroshio and its neighboring waters based on metabarcoding analysis of gut DNA content for major taxonomic groups of mesozooplankton and ichthyoplankton. Calanoids were found to be the most predominant and frequently appearing prey, whereas non-crustaceans were the secondary prey for most mesozooplankton and ichthyoplankton groups. Trophic networks based on gut DNA content demonstrated that calanoids were the most important sector with multiple linkages among their prey and predators, and gelatinous and non-crustacean mesozooplankton were the secondary sectors. These findings suggest that calanoids are important hubs of trophic pathways toward ichthyoplankton, and that gelatinous and non-crustacean mesozooplankton groups strengthen trophic relationships with multiple components. Contrary to general thought, our metabarcoding analysis has revealed that trophodynamics toward ichthyoplankton are not strongly dependent on the grazing food chain, but are supported by multiple trophic pathways in the Kuroshio and its neighboring waters.

DOI： 10.1016/j.pocean.2024.103356

Scopus

髙﨑蒼, 志水勝好, 小針統, 幅野明正, 中村啓彦, 内海真生, 千村涼 . 高光合成植物ケナフを用いた二酸化炭素深海貯蔵 . 環境科学会誌37 ( 4 ) 131 - 137 2024年7月

記述言語：日本語出版者・発行元：社団法人環境科学会

温室効果ガスであるCO2排出量を減らす取り組みが世界各国で行われている。しかしこれらの取り組みで，CO2排出量は減少するが，これまで大量に空気中へ排出されてきたCO2の絶対量は低下せず，大気中CO2濃度も低下しない。すなわち空気中のCO2を除去しなければ，今後現在以上の地球温暖化の進行を招く。そのためネガティブエミッション技術（大気中のCO2を回収・吸収し，貯留または固定化等を組み合わせることにより，正味としてマイナスのCO2排出量を達成する技術）の利用が必要である。本研究の目的は光合成能力が高くCO2を固定量が多いと考えられるケナフ（Hibiscus cannabinus L.）を栽培し，深海に貯蔵することによりケナフによるネガティブエミッション技術の可能性を明らかにすることである。CO2回収・吸収の評価として2020年および2022年に供試品種にはEverglades 41を用い，2020年は株間が15 cmと30 cm, 2022年は株間10 cm, 20 cmで栽培し，効率的なCO2固定のための栽植密度を明らかにした。CO2貯留・固定化に関する実験として2018年にケナフの主茎を30 cm程度に切断し，それらを5本ずつ網袋に入れ，2019年6月に沖縄県近くの東シナ海（N27°02.634′ E125°56.632′）の水深606 mで貯留した。そして2020年9月に回収した。深海係留前の乾物重と比較して深海貯蔵による影響を調査した。その結果ケナフの茎は深海貯蔵前後で乾物重に差は見られなかった。また走査電子顕微鏡観察で，生物による食害の形跡は観察されなかったことから，生物による食害・分解は行われていないものと考えられた。以上のことから，ケナフによるCO2の深海貯蔵の可能性が明らかとなった。

DOI： 10.11353/sesj.37.131

Liu H., Gilmartin J., Sluis M.Z., Kobari T., Rooker J., Bi H., Quigg A. . Dynamic oceanographic influences on zooplankton communities over the northern Gulf of Mexico continental shelf . Journal of Sea Research199 102501 2024年6月査読国際共著

記述言語：英語出版者・発行元：Journal of Sea Research

Dynamic influences of ocean processes on distribution, abundance, and diversity of zooplankton communities were studied over the continental shelf in the northern Gulf of Mexico (GoM) from 2015 to 2017. Zooplankton sampling was conducted on four summer cruises in the northcentral GoM. Sampling was designed in waters potentially influenced by the Loop Current (LC) and/or Mississippi River discharge to assess the impacts of these two mesoscale features on the abundance and diversity of zooplankton. During the three-year study, the LC displayed distinct spatial-temporal variations in penetration and occurrence in the northern GoM. Environmental conditions (i.e., sea surface temperature, salinity, and dissolved oxygen) varied between months and years sampled, and were significantly different among cruises (ANOVA, p < 0.001). The majority of zooplankton consisted of calanoid copepods (65% ± 7.2%, mean ± SD), while non-copepod taxa were primarily chaetognaths, polychaetes, tunicates, and ostracods (23 ± 9.2%). Species abundance and diversity of zooplankton were significantly correlated with sea surface temperature, salinity, and dissolved oxygen (p < 0.05). Canonical correspondence analysis displayed significant associations between mesoscale features and dominant zooplankton groups among cruises and by taxa (Monte Carlo Permutation Test, p < 0.001). In addition, non-metric multidimensional scaling indicated that zooplankton assemblages were distinct, likely caused by Mississippi River plumes during the study period. As one of the few efforts to examine zooplankton dynamics at a low taxon level over the GoM continental shelf regarding the impact of mesoscale features, this study revealed seasonal (i.e. summer) and spatial patterns in distribution, abundance, and diversity of zooplankton communities subjected to the dynamic physicochemical conditions in the northern GoM, which will continue in a changing climate.

DOI： 10.1016/j.seares.2024.102501

Scopus

Komorita T., Kobari T., Kume G., Kako S., Habano A., Arita Y., Makino F., Ichinomiya M. . Temporal changes in the microplankton community due to Kuroshio branch current inflow . Regional Studies in Marine Science75 103576 - 103576 2024年5月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Regional Studies in Marine Science

Inflow from the Kuroshio Current into coastal areas stimulates biological production. However, to date there are no detailed reports on its temporal changes. In the target area of this study, Kagoshima Bay, Japan, the time of inflow of the Kuroshio branch current can be identified a posteriori based on water temperature data. This study aimed to determine the relationship between the Kuroshio branch current inflow from the surface layer and phytoplankton bloom at the mouth of the bay during the mixing season. Therefore, we compiled data from ship observations in the Kagoshima Bay from 2016 to 2019 to examine changes in water quality (temperature, salinity, and nutrients), microphytoplankton, and microzooplankton versus time since current inflow. In this study, significant relationships were obtained for microplankton in terms of both biomass and cell abundance, and specific growth rates (0.060–0.079 d–1) comparable to that of chlorophyll a. In addition, the current inflow provided nutrients to the surface in the absence of strong wind and waves. Over time, phytoplankton, mostly athecate dinoflagellates, as well as microzooplankton, mainly naked ciliates, proliferated and were quickly preyed upon by mesozooplankton. Over the study period, such events could be observed once every two weeks in most years, suggesting that these frequent phytoplankton blooms support the high biomass of mesozooplankton and larval fish found in this area.

DOI： 10.1016/j.rsma.2024.103576

Scopus

Kobari T., Honma T., Kodama M., Kodama A., Watanabe T., Takikawa T. . Spatial and temporal variations in community structure, standing stock and productivity of mesozooplankton in the southwestern Japan Sea . Plankton and Benthos Research19 ( 1 ) 26 - 36 2024年2月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：日本プランクトン学会、日本ベントス学会

The Tsushima Strait and the neighboring waters has been known as major spawning and nursery grounds for migratory fishes due to the high standing stocks of the plankton community in spring to summer. In the present study, spatial and temporal variations in taxonomic composition, standing stocks and productivity of the mesozooplank-ton community were investigated in the southwestern Japan Sea to explore their variations during the productive sea-sons. Both spatial and temporal fluctuations were significant for mesozooplankton standing stocks while only temporal variability affected their productivity. The mesozooplankton community was split into one coastal group, represented by cladocerans and noctilucids throughout the seasons, and five pelagic groups, predominated by calanoids, cyclopoids and copepod nauplii, with temporal replacement during spring to summer. The coastal community group contained the additional standing stocks of cladocerans and noctilucids along with the predominant copepods from the other groups and thus resulted in the spatial difference in mesozooplankton standing stocks between coastal and pelagic sites. Three pelagic community groups were characterized by the abundant appearance of noctilucids and clustered toward the pelagic stations neighboring the coastal community group. Generalized linear models demonstrated that salinity was a significant explanatory variable for standing stocks of mesozooplankton and coastal taxonomic groups (i.e., cladocerans and noctilucids). These findings suggest that the spatial and temporal variations in mesozooplankton standing stocks are a mixture of the pelagic community groups with the coastal community group advected toward the pelagic sites.

DOI： 10.3800/pbr.19.26

Scopus

CiNii Research

小針統, 中谷颯人, 後藤慎之介, 津田周平, 牧野文洋, 東隆文, 小森田智大, 一宮睦雄, 小玉将史, 久米元 . 薩南海域に来遊するブリ稚魚の餌料源 . 水産海洋研究87 ( 4 ) 209 - 217 2023年11月査読

担当区分：筆頭著者,　責任著者記述言語：日本語出版者・発行元：一般社団法人水産海洋学会

ブリ稚魚は海面養殖の天然種苗として利用されてきたが，初期成長を支える餌料源に関する情報は少ない．本研究では，安定同位体比およびメタバーコーディング解析により，薩南海域に来遊するブリ稚魚の初期成長を支える餌生物および餌料源を明らかにした．ブリ稚魚の筋肉組織の炭素・窒素安定同位体比は，黒潮域の水柱内に分布する動物プランクトンおよびブリ稚魚以外の仔稚魚と近似した．ブリ稚魚の消化管内容物から検出された遺伝子では，カラヌス目カイアシ類が最も優占し頻出する餌生物であった．小型稚魚ではポエキロストム目カイアシ類，大型稚魚では尾虫類・毛顎類がこれに次ぐ餌生物であった．また，消化管内のカラヌス目カイアシ類が増加すると，ブリ稚魚の成長指数も増加する傾向を示した．これらの結果は，流れ藻に随伴して薩南海域に来遊するブリ稚魚が，流れ藻の葉上動物ではなく水柱内の動物プランクトンを餌料源として成長することを示唆する．

DOI： 10.34423/jsfo.87.4_209

CiNii Research

Tomiyasu T., Matsuki H., Oda M., Kodamatani H., Kanzaki R., Kobari T. . Impact of mercury discharged from submarine volcano on inner bay ecosystems . Chemosphere339 139748 - 139748 2023年10月査読国際誌

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemosphere

Organic mercury, inorganic mercury and total mercury concentrations in phytoplankton (<0.1 mm) and zooplankton (>0.1 mm) collected in Kagoshima Bay, Japan were measured from 2017 to 2019 to estimate the impact of mercury discharged from submarine volcanoes on ecosystems; submarine volcanic activity continues at a depth of 200 m in the inner part of Kagoshima Bay. The total mercury concentrations in phyto- and zooplankton collected by vertical hauling at 0–200 m at just above the submarine volcano were in the range of 0.11–2.0 mg kg−1 (avg. 0.67 mg kg−1) and 0.090–0.56 mg kg−1 (avg. 0.21 mg kg−1), respectively. These values were one order of magnitude higher than the values in plankton collected in the central part of Kagoshima Bay. Organic mercury concentrations in phyto- and zooplankton were <0.010–0.071 mg kg−1 (avg. 0.028 mg kg−1) and 0.012–0.25 mg kg−1 (avg. 0.10 mg kg−1), respectively, for the inner part, and <0.010–0.040 mg kg−1 (avg. 0.010 mg kg−1) and <0.010–0.025 mg kg−1 (avg. 0.012 mg kg−1), respectively, for the central part. The values obtained in the inner part of the bay increased in summer and decreased in winter, which was consistent with changes in seawater mercury concentrations affected by volcanic activity. The organic mercury concentration in zooplankton collected just above the submarine volcano showed a size dependency, and a higher value was observed in the larger size, which suggested that the discharged mercury from the volcano was absorbed and concentrated through the ecosystem.

DOI： 10.1016/j.chemosphere.2023.139748

Scopus

PubMed

Kume G., Nakaya K., Takeda T., Ichinomiya M., Komorita T., Habano A., Makino F., Kodama M., Kobari T. . Distribution and growth rates of Japanese jack mackerel Trachurus japonicus larvae relative to oceanographic conditions in the northern Satsunan area, southern Japan . Plankton and Benthos Research18 ( 3 ) 148 - 159 2023年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：日本プランクトン学会、日本ベントス学会

The northern Satsunan area, comprising the mouth of Kagoshima Bay and Osumi Strait, is an important spawning and nursery ground for Japanese jack mackerel Trachurus japonicus in Japan. Upwellings frequently occur at the mouth of the bay during winter and spring, and the consequent nutrient supply promotes phytoplankton blooms. This study examined how T. japonicus utilizes upwelling (Kagoshima Bay) and non-upwelling areas (Osumi Strait) as larval nursery grounds. Densities and growth rates (measured as the average width of the last three otolith increments) of T. japonicus larvae in both areas were compared to determine the upwelling influence on nursery ground formation. The mouth of the bay had lower temperature and salinity but higher chlorophyll-a concentrations and prey density than that of the strait. Densities of larvae were consistently higher in the bay than in the strait, indicating that the main nursery of T. japonicus is formed in Kagoshima Bay. No significant differences were observed in the growth rates of larvae among areas, suggesting that lower temperatures and prey availability are growth limiting factors in the mouth of the bay and the strait, respectively, and the Osumi Strait could also provide a favorable nursery area.

DOI： 10.3800/pbr.18.148

Scopus

CiNii Research

Masafumi Kodama, Ryoga Yamazaki, Jun Hayakawa, Gakuto Murata, Ko Tomikawa, Tomohiko Kawamura, Gen Kume, Toru Kobari . Feeding ecology of the obligate urchin symbiont Dactylopleustes yoshimurai (Crustacea: Amphipoda: Pleustidae) revealed by DNA metabarcoding analysis. . 2023年4月査読

担当区分：最終著者出版者・発行元：Research Square Platform LLC

Abstract

Symbiosis includes commensalism, mutualism, and parasitism, however in many symbiotic relationships, it is difficult to determine which type they are in. Since trophic-linkage is a necessary factor to determine this, data on feeding ecology of symbionts is essential to understand symbiont-host relationships. Amphipods of the genus Dactylopleustes are known as obligate urchin symbionts. Though their ecology remains largely unknown, Dactylopleustes was recently reported to aggregate on diseased hosts, suggesting that Dactylopleustes feeds on diseased urchins’ tissues and uses urchins as both a habitat and prey. We investigated by DNA metabarcoding analyses, the feeding ecology of Dactylopleustes yoshimurai in relation to growth and whether host is disease or not. Contrary to our hypothesis, sequence reads from the gut contents were dominated by planktonic copepods regardless of body size or host disease. These results suggest that they mainly feed on copepod fecal pellets deposited on sediments, and do not have a strong trophic-linkage with their host. Large individuals on diseased urchins feed more on urchins than those on healthy urchins. However, their main prey still remains copepods, implying that host disease has a limited effect on the feeding behavior. In conclusion, our study supports this species is not a strong parasite but more of a commensal of urchins.

DOI： 10.21203/rs.3.rs-2655652/v1

その他リンク： https://www.researchsquare.com/article/rs-2655652/v1.html

Chang F.H., Lin Y.C., Chiang K.P., Nien Y.H., Hsieh C.H., Chen W.J., Hung C.C., Kobari T., Saito H., Savidge W. . Editorial: Oceanographic processes linking nearshore, continental shelf, and shelf break . Frontiers in Marine Science10 2023年1月査読

Kobari T., Shinyashiki M., Saito K., Kume G., Ichinomiya M., Komorita T., Miyamoto H., Okazaki Y., Makino F., Fukuda R., Hyodo F., Noguchi-Aita M. . Trophic sources and pathways of mesozooplankton and fish larvae in the Kuroshio and its neighboring waters based on stable isotope ratios of carbon and nitrogen . Progress in Oceanography210 102952 - 102952 2022年12月査読

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress in Oceanography

Major forage fishes spend their vulnerable early life stages in the Kuroshio and its neighboring waters where phytoplankton standing stocks are much lower than in coastal areas. Nevertheless, little is known of how mesozooplankton and fish larvae with their high biodiversity are supported in the Kuroshio ecosystem. Here we report stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) for mesozooplankton and fish larvae from coastal to pelagic sites in the East China Sea to evaluate trophic sources and pathways at lower trophic levels in planktonic food webs under different environmental regimes. Although δ13C and δ15N in mesozooplankton and fish larvae varied among taxonomic groups and sites, mesozooplankton δ13C and δ15N tended to be lower for particle-feeders than carnivores and fish larvae and at more pelagic sites than in coastal waters. There were significant linear regressions between δ15N and δ13C of mesozooplankton communities, with the similar slopes among sites and lower intercepts at more pelagic sites. The δ15N and δ13C of small copepods, euphausiids, ostracods, appendicularians and fish larvae were aligned close to the regression line covering all regions, indicating that these were trophic sources and pathways to mesozooplankton and fish larvae. Our results suggest that trophic sources of mesozooplankton and fish larvae are supported through copepods and appendicularian-integrated microbial production and are more dependent on diazotrophic production in more pelagic waters.

DOI： 10.1016/j.pocean.2022.102952

Scopus

数野真, 加古真一郎, 中村啓彦, 山城徹, 仁科文子, 久米元, 小針統 . 高分解能沿岸海洋モデルの粒子追跡による黒潮への黒潮内側域水塊移流の評価 . 水産海洋研究86 ( 4 ) 153 - 165 2022年11月査読

担当区分：責任著者記述言語：日本語出版者・発行元：一般社団法人水産海洋学会

貧栄養である黒潮でも，黒潮内側域の水塊移流がプランクトン現存量や生産力を増大させる可能性が指摘されているが，情報が限られている．そこで本研究では，高分解能沿岸海洋モデルにおける粒子追跡実験により，黒潮へ移流する黒潮内側域の水塊の供給源および移流過程を再現した．黒潮フロントで頻発する蛇行や渦などの擾乱に遭遇することで，黒潮内側域から黒潮域への水塊移流が励起されていた．沿岸水の供給源としては，トカラ海域での定常的な移流が最も大きく，東シナ海での冬期から春期の移流も貢献した．黒潮内側域から黒潮域への動物プランクトン移流量は，黒潮内での動物プランクトン輸送量の2–44%に相当し，九州南方海域から九州東方海域での移流が貢献した．黒潮内側域から移流する動物プランクトンの生物量は，黒潮内の動物プランクトンの成長による増分に匹敵し，黒潮における魚類群集の餌要求を支えている可能性がある．

DOI： 10.34423/jsfo.86.4_153

CiNii Research

Mutsuo Ichinomiya, Takehito Nomiya, Tomohiro Komorita, Toru Kobari, Gen Kume, Akimasa Habano, Yoichi Arita, Fumihiro Makino . Seasonal variation in the environments, biomass and community structure of microplankton in the northern Satsunan area, the west Japan . Journal of Marine Systems234 103767 - 103767 2022年10月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Marine Systems

Seasonal variations in hydrographic conditions, nutrients, and microplankton abundance and biomass were investigated inside and outside Kagoshima Bay in the northern Satsunan area. The area is a nursery ground for the migrating fish. During the mixing season from November to April, highly saline water (>34.5) originating from a branch of the Kuroshio Current, the western boundary current of the North Pacific Subtropical Gyre, intruded from the surface layer into the bay causing extrusion of coastal bottom water. This intrusion generated vertical mixing between surface water and nutrient-rich bottom water. Consequently, chlorophyll a concentrations increased (>1 μg l−1) around the bay mouth. During the stratified season from May to August, the coastal surface water was extruded due to intrusion of saline water from the bottom layer. High chlorophyll a concentrations (>1 μg l−1) were also observed in the surface layer in July during the rainy season. Such differences in hydrographic conditions between mixing and stratified seasons were due to vertical distribution of highly saline water from outside the bay, which seasonally migrated between surface and subsurface layers. Relatively distinct redundancy analysis plots and boxplots generated from a generalized linear model showed that microplankton community structure differed between mixing and stratified seasons. The mixing and stratified seasons were characterized by high diatom abundance and low microplankton abundance, respectively, suggesting that vertical mixing increases nutrient supply and consequently increases diatom abundance. Thus, microzooplankton (mainly naked ciliates and athecate dinoflagellates) abundance was related to the abundance of prey organisms, such as diatoms, thecate dinoflagellates and cryptophyte-like flagellates, rather than hydrographic conditions. Thus, saline water intrusion from a branch of the Kuroshio Current likely governs hydrographic conditions in Kagoshima Bay and consequently affects temporal variations in abundance and taxonomic composition of phytoplankton and microzooplankton communities.

DOI： 10.1016/j.jmarsys.2022.103767

Scopus

眞子裕友, 小針統, 一宮睦雄, 小森田智大, 幅野明正, 東隆文, 久米元 . 黒潮およびその周辺海域における仔稚魚の成長活性 . 日本プランクトン学会報69 ( 2 ) 93 - 101 2022年8月査読

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：日本プランクトン学会

It has been thought that food availability for fish larvae was poor in the Kuroshio because of the low standing stocks of plankton in the oligotrophic conditions under thermal stratification throughout the year. Despite a potential risk or disadvantage for larval survival and growth, Kuroshio and its neighbouring waters are nursery grounds for the early life stages of various fishes. Here, we compared the growth activity of fish larvae among 15 taxonomic groups, including 11 families in the Kuroshio and its neighbouring waters, based on protein synthetase activity and protein contents. Protein-specific (spAARS), individual-based aminoacyl tRNA synthetase activities (iAARS), and protein contents (PRO) of fish larvae ranged from 2 to 232 nmol PPi mg protein−1 h−1, from 1 to 21 μmol PPi ind−1 d−1, and from <1 to 26 mg ind−1, respectively. spAARS, iAARS and PRO were variable among the taxonomic groups and were not classified between mesopelagic groups and the others. Compiling these measurements among all taxonomic groups, a significant negative correlation was found for spAARS to PRO. The correlation showed no significant difference between the Kuroshio and its neighbouring coastal waters, indicating that growth activities to fish larvae body mass were comparable in the Kuroshio and its neighbouring waters. Based on nonmetric multidimensional scaling on spAARS, iAARS and PRO among 15 taxonomic groups, two different groups were classified for fish larvae, represented by the high iAARS under the high PRO but low spAARS (Group 1) and the low iAARS under the low PRO but high spAARS (Group 2), representing the different life strategies for larval growth among the taxonomic groups. The present findings suggest that these biochemical indices are useful for evaluating the growth activity of fish larvae among various taxonomic groups and that food availability is not poor enough to support larval growth in the Kuroshio and its neighbouring waters.

DOI： 10.24763/bpsj.69.2_93

Scopus

CiNii Research

眞子裕友, 小針統, 一宮睦雄, 小森田智大, 幅野明正, 東隆文, 久米元 . 黒潮およびその周辺海域における仔稚魚の成長活性 . 日本プランクトン学会報69 93 - 101 2022年8月査読

Kobari T. . Mesopelagic community supported by epipelagic production in the western North Pacific Ocean based on stable isotope ratios of carbon and nitrogen . Deep-Sea Research Part I: Oceanographic Research Papers182 103722 - 103722 2022年4月査読

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Deep-Sea Research Part I: Oceanographic Research Papers

We compared stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) of epi- and mesopelagic mesozooplankton communities at subarctic (K2) and subtropical (S1) sites in the North Pacific Ocean to evaluate the relationship between mesopelagic communities and epipelagic production. Although δ13C and δ15N varied among the taxonomic groups, ostracods, carnivorous copepods, and chaetognaths tended to exhibit higher δ13C and δ15N than omnivorous copepods within the same layers. Mesozooplankton δ13C and δ15N were higher in the upper (200–500 m) and lower (500–1000 m) mesopelagic layers than in the epipelagic layer (0–150 m). δ13C and δ15N of mesozooplankton were positively correlated at all three depth-ranges at both sites. Although the slopes of linear regressions of δ15N vs. δ13C exhibited no significant differences among layers or between sites, the intercept was lower for mesozooplankton at S1. We attributed the similarity of slopes to common isotopic fractionation during protein synthesis among the different taxonomic groups, and the lower intercept to primary producers supported by recycled nutrients and atmospheric nitrogen fixation under the high thermal regime at S1. Our results further confirm earlier evidence that metabolic requirements of mesopelagic communities are supported by epipelagic production through the biological pump.

DOI： 10.1016/j.dsr.2022.103722

Scopus

眞子裕友, 小針統, 久米元, 兵藤不二夫, 野口真希, 一宮睦雄, 小森田智大, 河邊玲, 中村乙水, 米山和良, 土田洋之 . 北部薩南海域に来遊したジンベエザメの餌生物 . 日本プランクトン学会報69 ( 1 ) 18 - 24 2022年2月査読

記述言語：日本語出版者・発行元：日本プランクトン学会

The prey of whale sharks (Rhincodon typus) visiting the northern Satsunan area (western North Pacific Ocean) was investigated using microscopic and metabarcoding analysis of their faecal pellets. The stable isotope ratios of the dorsal fin and faecal pellets from the whale sharks were compared with those of their potential prey (plankton and fish larvae). Microscopic analysis identified protozoans (foraminifera) and metazoans (copepods, ostracods, and amphipods) but unclassified material was predominant in their faecal pellets. Metabarcoding analysis detected metazoans in the faecal pellets, represented by copepods, ostracods, amphipods, hydrozoans, and tunicates. Comparison of stable isotope ratios (δ13C and δ15N) from their dorsal fin and faecal pellets with those of zooplankton in the northern Satsunan area showed different feeding histories for the whale sharks appearing in the northern Satsunan area.

DOI： 10.24763/bpsj.69.1_18

Scopus

CiNii Research

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