Planktonic metabolism plays an important role in affecting the energy transportation and carbon cycle of themarine ecosystem. However, its regulation mechanism remains unclear under the continuously exogenous nutrient inputs in nearshore waters. In this study, a mesocosm experiment was conducted in a semi-enclosed bay, the Daya Bay, to explore the responses of plankton metabolic balance and community structure to a conce-ntration gradient of daily nitrogen and phosphorus inputs. The results showed that nutrient enrichments promoted phytoplankton biomass, total primary production, and community respiration, and the promoting effect enhanced alongwith the increase of nutrient concentration. However, the net community production fluctuated more violently between autotrophic and heterotrophic with the increase of nutrient inputs and tended to be more heterotrophic from the 5th day to the 10th day of the experiment. In addition, the daily flux of nitrogen and phosphorus, 2 μmol/(L·d) and 0.066 μmol/(L·d), respectively, could be regarded as a potential threshold for ecosystem stability and health, since most of the ecological characteristics related to plankton structure and function have undergone significant changes when the nutrient level is higher than that. In the nearshore enclosed or semi-enclosed waters, nutrient from continuous terrigenous input is likely to be concentrated and exceed this level, indicating the ecological risks due to the metabolic unbalance and the deterioration of plankton community structure.

Chenhui Xiang;Yao Li;Zhixin Ke;Gang Li;Yadong Huang;Xinying Su;Liangmin Huang;Xinyu Song

Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 510301, China;Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 510301, China;University of Chinese Academy of Sciences, Beijing 100049, China;Nansha Marine Ecological and Environmental Research Station, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China

海洋学报（英文版）

[1]Chenhui Xiang;Yao Li;Zhixin Ke;Gang Li;Yadong Huang;Xinying Su;Liangmin Huang;Xinyu Song-.Effects of daily nitrogen and phosphorus input on planktonic community metabolism in a semi-enclosed bay by mesocosm experiment)[J].海洋学报（英文版）,2022(08):99-110,中插22-中插24

Planktonic,themarine,Daya,conce,ntration,alongwith

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