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Studies on the Biogeochemical Roles of the SML

海面ミクロ層 Sea surface microlayer

海表面マイクロレイヤー(sea surface microlayer, SML)とは、海洋の最表層わずか1 mm(1,000 µm)未満の層のことです。大気と海洋の境界に位置しているため、気体(CO2, CH4, CO, N2Oなどの温室効果ガスを含む)や粒子の大気-海洋間の交換を介して、生物地球化学的な物質循環および気候変動に重要な役割を果たしていると考えられています。


海表面マイクロレイヤーは、強い太陽光(特に紫外線)に曝されている、有機物・微生物が集積している、微生物の群集構造が異なることなどから、水深0.5−1 m程度の海面直下(subsurface water, SSW or underlying water, ULW)と物理的・化学的・生物学的に異なる環境を形成しています。しかし、海表面マイクロレイヤーにおける有機物・微生物の集積および化学的・生物学的プロセスが大気-海洋間の気体や粒子の交換に与える影響については、ほとんど明らかにされていません。

The sea surface microlayer (SML) is defined as less than 1-mm (1,000-µm) thick uppermost layer of the ocean water column. Because it is located at the air-sea interface, the SML is considered to play critical roles in global biogeochemical cycles and climate change through the regulation of the air-sea exchange of gases (including greenhouse gases such as CO2, CH4, CO, and N2O) and particles.


Due to exposure to intense solar radiation (especially UV light), the accumulation of organic matter and microorganisms, and different microbial community structure, the SML forms physically, chemically, and biologically distinct environments compared to the subsurface water (SSW) or underlying water (ULW) at 0.5−1 m depth. However, the infomation on the effect of the accumulation of organic matter/microorganisms and chemical/biological processes in the SML on the air-sea exchange of gases and particles has remained limited.






・ SMLにおける微生物の群集構造および溶存気体の代謝能


・ SMLにおける化学的/生物学的パラメーターの時空間変動およびSMLの形成要因

Research Themes (e.g.)


・ Gas production and consumption in the SML and their effect on air-sea gas exchange


・ Microbial community structure and the metabolic capability of dissolved gases in the SML


・ Temporal and spatial variations in chemical and biological parameters in the SML and the

factors of the SML formation

関連論文  Related Papers


Youta SUGAI, K. Tsuchiya, S. Shimode, T. Toda (2020)


Photochemical Production and Biological Consumption of CO in the SML of Temperate Coastal Waters and Their Implications for Air-Sea CO Exchange


Journal of Geophysical Research: Oceans, 125, doi: 10.1029/2019JC015505


Youta SUGAI, K. Tsuchiya, S. Shimode, T. Toda (2018)


・ Seasonal variation in microbial abundance and transparent exopolymer particle concentration in the sea surface microlayer of temperate coastal waters


Aquatic Microbial Ecology, 81, 201−211


Studies on the Microbial Loop in the Ocean

微生物ループ Microbial loop

関連論文  Related Papers


・ Youta SUGAI, N. Natori, K. Tsuchiya, M. Nakagawa, M. C. Honda, S. Shimode, T. Toda (2023)


・ Ingestion rate estimated from food concentration and predatory role of copepod nauplii in microbial food web of temperate embayment waters


・ Journal of Plankton Research, 45, 325−337


Youta SUGAI, K. Tsuchiya, V. S. Kuwahara, S. Shimode, K. Komatsu, A. Imai, T. Toda (2016)


Bacterial growth rate and the relative abundance of bacteria to heterotrophic nanoflagellate in the euphotic and disphotic layers in temperate coastal waters of Sagami Bay, Japan


Journal of Oceanography, 72, 577−587


「2018年度 日本海洋学会 奨励論文賞」受賞


Be awarded "The Young Author Award 2018 of The Oceanographic Society of Japan"

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