Effects of phosphorus limitation on sinking velocities of phyto-plankton during summer in the Changjiang River Estuary

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外文摘要：The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted during the summer of 2022 in the Changjiang River(Yangtze River)Estuary(CJE)and its adjacent waters.The settling column method was employed to measure the sinking velocity(SV)of different size fractions of phytoplankton at the surface of the sea and to analyze their environmental control mechanisms.The findings reveal significant spatial variation in phytoplankton SV(-0.55-2.41 m/d)within the CJE.High-speed sinking was predominantly observed in phosphate-depleted regions beyond the CJE front.At the same time,an upward trend was more commonly observed in the phosphate-rich regions near the CJE mouth.The SV ranges for different size-fractionated phytoplankton,including micro-(＞20 μm),nano-(2-20 μm),and picophytoplankton(0.7-2 pm),were-0.50-4.74 m/d,-1.04-1.59 m/d,and-1.24-1.65 m/d,respectively.Correlation analysis revealed a significant negative correlation between SV and dissolved inorganic phosphorus(DIP),implying that the influence of DIP contributes to SV.The variations in phytoplankton alkaline phosphatase activity suggested a significant increase in SV across all size fractions in the event of phosphorus limitation.Phytoplankton communities with limited photosynthetic capacity(maximum photochemical efficience,Fv/Fm＜0.3)were found to have higher SV than that of communities with strong capacity,suggesting a link between sinking and alterations in physiological conditions due to phosphate depletion.The findings from the in situ phosphate enrichment experiments confirmed a marked decrease in SV following phosphate supplementation.These findings suggest that phosphorus limitation is the primary driver of elevated SV in the CJE.This study enhances the comprehension of the potential mechanisms underlying hypoxic zone formation in the CJE,providing novel insights into how nearshore eutrophication influences organic carbon migration.

外文关键词：

phytoplanktonsinking velocityChangjiang River Estuaryphosphorus limitationalkaline phosphatase

作者：

Xinchi You、Qiang Hao、Jie Zhu、Wei Zhang、Haiyan Jin、Dewang Li、Huanhong Ji、Yu Ke、Feng Zhou

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作者单位：

Ocean College,Zhejiang University,Zhoushan 316021,China

State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310000,China

Key Laboratory of Marine Ecosystem Dynamics,Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China

Donghai Laboratory,Zhoushan 316021,China

East China Sea Ecological Center,Ministry of Natural Resources,Shanghai 201206,China

Key Laboratory of Marine Ecological Monitoring and Restoration Technologies,Ministry of Natural Resources,Shanghai 201206,China

Observation and Research Station of Yangtze River Delta Marine Ecosystems,Ministry of Natural Resources,Zhoushan 316021,China

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基金：

National Programme on Global Change and Air-Sea Interaction(Phase Ⅱ)—Hypoxia and Acidification Monitoring and Warning ProjecScience Foundation of Donghai LaboratoryOceanic Interdisciplinary Program of Shanghai Jiao Tong University and Scientific Research Fund of the Second Institute of ONational Key R&D Program of ChinaLongterm Observation and Research Plan in the Changjiang Estuary and Adjacent East China Sea(LORCE)Project

项目编号：

GASI-01-CJKDH-2022KF0215SL2022ZD2072021YFC3101702SZ2001

出版年：

2024

DOI：

10.1007/s13131-024-2376-x

海洋学报(英文版)

中国海洋学会

海洋学报(英文版)

CSTPCD

影响因子：0.323

ISSN：0253-505X

年,卷(期)：2024.43(6)