AUTHOR=Kim Bo Kyung , Jeon Misa , Park Sang-Jong , Kim Hyun-Cheol , Min Jun-Oh , Park Jisoo , Ha Sun-Yong 

TITLE=Variability in the Carbon and Nitrogen Uptake Rates of Phytoplankton Associated With Wind Speed and Direction in the Marian Cove, Antarctica

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.887909

DOI=10.3389/fmars.2022.887909

ISSN=2296-7745

ABSTRACT=Quantifying temporal variabilities in phytoplankton productivity is essential to improving our understanding of the carbon (C) and nitrogen (N) dynamics and energy flows in natural aquatic ecosystems. At 3-day intervals, samples to determine C and N (NO3- and NH4+) uptake by phytoplankton were collected from fixed stations, and by the effect of NH4+ concentrations on phytoplankton communities in December-January 2018/19 in Marian Cove, Antarctica. Considerable fluctuations in the total C and N productivities were observed, which resulted in dynamic changes in the phytoplankton communities and a stronger coupling between distinct phytoplankton biomasses. The increased rate of NO3- uptake coincided with an enhanced C uptake mainly by microphytoplankton (> 20 µm), followed by an increase in NH4+ uptake, and then an increase in NH4+ concentrations observed at the end of sampling. However, the < 2 µm fraction (picophytoplankton) showed little variation in C and NO3- uptake, and the proportions of assimilated NH4+ contributed to more than half of the total inorganic N assimilated. Clearly, the increased NH4+ did not support increased total phytoplankton biomass and C production. Interestingly, after the first two weeks of the sampling period, the C uptake rate decreased rapidly (< 3 mg C m-3 h-1 on 12 January) after a shift to a predominantly easterly wind (> 6 m s-1), during which time the phytoplankton community was replaced by neritic and ice-related species. These findings suggest that the strong temporal shifts in phytoplankton C assimilation were strongly influenced by external forces (wind stress).