Factors affecting the massive phytoplankton bloom in the Amundsen Sea, Antarctica

Amundsen Sea Polynya is one of the most productive Antarctic coastal polynyas, where highest chlorophyll concentrations on the surface are often found to be >10 mg m^-3 during the austral summer. We have conducted three years of intensive surveys using Fluorescence Induction and Relaxation (FIRe) in the Amundsen Sea which covered both early and late austral summer. Our analysis revealed a conspicuous negative relationship between chlorophyll-a concentration and maximum quantum efficiencies of photosystem II (F_v/F_m ) in the near surface ocean. The measurements of phytoplankton photophysiology showed that F_v/F_m values were relatively lower in the polynya center than near polynya edges, which imply unfavorable chemical conditions for phytoplankton growth, due to iron limitation. Then, the extremely high phytoplankton biomass in the Amundsen Sea Polynya central region seems to be not easily explained by Fe alone. We will talk about why this phenomenon is showing in the Amundsen Sea Polynya.