Spatial Variability of Phytoplankton Communities in the Ross Sea: Insights from High-Resolution Observations

The Ross Sea is a critical region for understanding phytoplankton dynamics and their role in polar marine ecosystems in the west Antarctica, particularly in the context of rapid environmental change. Investigating the spatial variability of phytoplankton biomass and community structure is essential for assessing ecosystem productivity and biogeochemical cycling in this vulnerable area. From January to February 2023, a field survey of the Ross Sea was conducted onboard the icebreaker research vessel Araon, utilizing high-resolution, continuous observations of surface seawater with the Algae Online Analyzer and Imaging FlowCytoBot. These observations provided precise spatial distribution data on phytoplankton biomass and species abundance. The results revealed intricate spatial variability in phytoplankton community structure and biomass across the eastern and western Ross Sea, spanning coastal to offshore gradients, and in the dynamic waters near polynyas and ice shelves. The phytoplankton community was predominantly composed of diatoms, especially Fragilariopsis spp., and/or Phaeocystis spp., with their dominance varying across spatial gradients. The observed patterns suggest that multiple interacting environmental factors, including sea ice concentrations, water masses, and ocean currents, influence on phytoplankton distribution in the region. These findings highlight the critical role of physical and biological interactions in phytoplankton distributions and offer valuable insights into their potential responses to environmental changes in the Ross Sea ecosystem.