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<p>The Ross Sea is one of the most biologically productive regions in the Antarctic Ocean, characterized by predictable phytoplankton blooms. However, the northwestern Ross Sea remains a poorly studied area within this system, leaving significant gaps in understanding the environmental drivers regulating phytoplankton dynamics. The two dominant phytoplankton taxa in this region, diatoms and <i>Phaeocystis antarctica</i>, exhibit spatiotemporal variability in dominance, yet the factors influencing their distribution in this understudied area are not well constrained. This study investigated spatiotemporal distribution of diatoms and <i>P. antarctica</i> using high-performance liquid chromatography (HPLC) pigment analysis and identified key environmental factors influencing their composition in the northwestern Ross Sea during the summers of 2018 and 2019. In 2018, phytoplankton were predominantly composed of diatoms (66.6 ± 26.6%) and <i>P. antarctica</i> (30.2 ± 27.3%). Diatom dominance was negatively correlated with SiO<sub>2</sub> and dissolved inorganic nitrogen (DIN) concentrations, whereas <i>P. antarctica</i> dominated in areas with relatively deeper mixed layer depths (123.7 ± 41.5&#xa0;m). In 2019, phytoplankton assemblage was more diverse, consisting of diatoms (48.0 ± 17.7%), <i>P. antarctica</i> (35.6 ± 18.2%), chlorophytes (7.7 ± 10.9%) formed the primary assemblages. Principal component analysis (PCA) suggested that <i>P. antarctica</i> played a significant role in nutrient depletion. Contrary to previous studies, <i>P. antarctica</i> was abundant even where the mixed layers were shallower than the euphotic depth, indicating a more complex relationship between phytoplankton composition and physical oceanographic conditions. Chlorophytes exhibited a distinct association with coastal melt water, contributing up to 45.9% of the phytoplankton in these areas. The strong correlation between chlorophytes and melting water suggests their introduction through sea ice melt, potentially influencing the phytoplankton structure under changing environmental conditions. These findings highlight the interactive effects of environmental variables on phytoplankton composition, emphasizing the importance for continued research on ice associated-shifts in species assemblages under ongoing environmental changes.</p>

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Major environmental controlling factors for phytoplankton assemblage composition in the northwestern ross sea during the summer periods, 2018 and 2019

  • 期刊论文

  • 发表日期：

    2025年12月29日

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  • Hyeju Yoo,
  • Eun Jin Yang,
  • Jisoo Park,
  • Sanghoon Park,
  • Yejin Kim,
  • Jaesoon Kim,
  • Sang Heon Lee

摘要

The Ross Sea is one of the most biologically productive regions in the Antarctic Ocean, characterized by predictable phytoplankton blooms. However, the northwestern Ross Sea remains a poorly studied area within this system, leaving significant gaps in understanding the environmental drivers regulating phytoplankton dynamics. The two dominant phytoplankton taxa in this region, diatoms and Phaeocystis antarctica, exhibit spatiotemporal variability in dominance, yet the factors influencing their distribution in this understudied area are not well constrained. This study investigated spatiotemporal distribution of diatoms and P. antarctica using high-performance liquid chromatography (HPLC) pigment analysis and identified key environmental factors influencing their composition in the northwestern Ross Sea during the summers of 2018 and 2019. In 2018, phytoplankton were predominantly composed of diatoms (66.6 ± 26.6%) and P. antarctica (30.2 ± 27.3%). Diatom dominance was negatively correlated with SiO2 and dissolved inorganic nitrogen (DIN) concentrations, whereas P. antarctica dominated in areas with relatively deeper mixed layer depths (123.7 ± 41.5 m). In 2019, phytoplankton assemblage was more diverse, consisting of diatoms (48.0 ± 17.7%), P. antarctica (35.6 ± 18.2%), chlorophytes (7.7 ± 10.9%) formed the primary assemblages. Principal component analysis (PCA) suggested that P. antarctica played a significant role in nutrient depletion. Contrary to previous studies, P. antarctica was abundant even where the mixed layers were shallower than the euphotic depth, indicating a more complex relationship between phytoplankton composition and physical oceanographic conditions. Chlorophytes exhibited a distinct association with coastal melt water, contributing up to 45.9% of the phytoplankton in these areas. The strong correlation between chlorophytes and melting water suggests their introduction through sea ice melt, potentially influencing the phytoplankton structure under changing environmental conditions. These findings highlight the interactive effects of environmental variables on phytoplankton composition, emphasizing the importance for continued research on ice associated-shifts in species assemblages under ongoing environmental changes.