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Article

Different Roles of Top-Down and Bottom-Up Processes in the Distribution of Size-Fractionated Phytoplankton in Gwangyang Bay

Department of Ocean Integrated Science, College of Fisheries and Ocean Sciences, Chonnam National University, Yeosu 59626, Korea
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Academic Editor: Gang Pan
Water 2021, 13(12), 1682; https://doi.org/10.3390/w13121682
Received: 8 June 2021 / Revised: 12 June 2021 / Accepted: 15 June 2021 / Published: 17 June 2021
(This article belongs to the Section Oceans and Coastal Zones)
The interactive roles of zooplankton grazing (top-down) and nutrient (bottom-up) processes on phytoplankton distribution in a temperate estuary were investigated via dilution and nutrient addition experiments. The responses of size-fractionated phytoplankton and major phytoplankton groups, as determined by flow cytometry, were examined in association with zooplankton grazing and nutrient availability. The summer bloom was attributed to nanoplankton, and microplankton was largely responsible for the winter bloom, whereas the picoplankton biomass was relatively consistent throughout the sampling periods, except for the fall. The nutrient addition experiments illustrated that nanoplankton responded more quickly to phosphate than the other groups in the summer, whereas microplankton had a faster response to most nutrients in the winter. The dilution experiments ascribed that the grazing mortality rates of eukaryotes were low compared to those of the other groups, whereas autotrophic cyanobacteria were more palatable to zooplankton than cryptophytes and eukaryotes. Our experimental results indicate that efficient escape from zooplankton grazing and fast response to nutrient availability synergistically caused the microplankton to bloom in the winter, whereas the bottom-up process (i.e., the phosphate effect) largely governed the nanoplankton bloom in the summer. View Full-Text
Keywords: top-down effect; bottom-up effect; phytoplankton bloom; flow cytometry; estuary; Gwangyang Bay top-down effect; bottom-up effect; phytoplankton bloom; flow cytometry; estuary; Gwangyang Bay
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MDPI and ACS Style

Kang, Y.; Oh, Y. Different Roles of Top-Down and Bottom-Up Processes in the Distribution of Size-Fractionated Phytoplankton in Gwangyang Bay. Water 2021, 13, 1682. https://doi.org/10.3390/w13121682

AMA Style

Kang Y, Oh Y. Different Roles of Top-Down and Bottom-Up Processes in the Distribution of Size-Fractionated Phytoplankton in Gwangyang Bay. Water. 2021; 13(12):1682. https://doi.org/10.3390/w13121682

Chicago/Turabian Style

Kang, Yoonja, and Yeongji Oh. 2021. "Different Roles of Top-Down and Bottom-Up Processes in the Distribution of Size-Fractionated Phytoplankton in Gwangyang Bay" Water 13, no. 12: 1682. https://doi.org/10.3390/w13121682

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