Bering Sea | Ecosystem Perspectives
Seasonal variations of export fluxes in the St. Lawrence Island Polynya region Presenter: Jacqueline Grebmeier, jgrebmei@umces.edu, University of Maryland Center for Environmental Science Catherine Lalande , catherine.lalande@kopri.re.kr Calvin Mordy , calvin.w.mordy@noaa.gov, CICOES, University of Washington, Seattle, WA, United States Phyllis Stabeno , phyllis.stabeno@noaa.gov, NOAA Pacific Marine Environmental Laboratory The St. Lawrence Island Polynya (SLIP), located south of St. Lawrence Island on the shallow continental shelf of the northern Bering Sea, is a highly productive area supporting large congregations of walruses, seals, and spectacled eiders. Recently, an unprecedented decline in sea ice cover in the SLIP region led to a redistribution of the phytoplankton bloom, with potentially important consequences for the bird and marine mammal populations. Despite extensive sampling in the SLIP region over the past decades, several months per year are not regularly sampled, including the critical period at the onset of the phytoplankton bloom occurring as early as March. To investigate seasonal variations in the pelagic ecosystem of the SLIP region, a sequential sediment trap was deployed next to the NOAA M8 oceanographic mooring, a line carrying multiple instruments anchored to the seafloor located within the Distributed Biological Observatory (DBO)1 site. The sediment trap collected sinking particles continuously from October 15, 2020 to August 31, 2021. Fluxes of chlorophyll a (chl a), total particulate matter (TPM), and particulate organic carbon (POC) were measured, while taxonomic analyses of phytoplankton and of zooplankton actively entering the sediment trap (swimmers) are ongoing. Chlorophyll a fluxes rapidly increased during May, peaked in early June, and gradually decreased from June to August, indicating the onset and export of a bloom in late May and June 2021. Peaks in TPM and POC fluxes during the last week of June suggest a main source of particulate matter other than primary production at that time, while sustained TPM, POC, and chl a fluxes from December to March suggest the resuspension of sediments and algae containing chl a during winter. An additional sediment trap has been deployed to collect sinking particles at the M8/DBO1 site from November 12, 2021 to September 1, 2022. The impact of changes in sea ice cover on the timing, intensity and composition of primary and secondary production in the SLIP region will be investigated when the sediment trap will be recovered in 2023.
Alaska Marine Science Symposium 2023 170
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