Arctic | Lower Trophic Levels
Increasing importance of the marine cyanobacteria Synechococcus in a warming Chukchi Sea Presenter: Michael W Lomas , mlomas@bigelow.org, Bigelow Laboratory for Ocean Sciences Lisa Eisner , lisa.eisner@noaa.gov, Alaska Fisheries Science Center, NOAA Fisheries Jens Nielsen , jens.nielsen@noaa.gov, Cooperative Institute for Climate, Ocean, and Ecosystem Studies, University of Washington Miranda Hart , mmsirby@ncsu.edu Priscila Lange , prilange@gmail.com, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil Astrid Schnetzer , aschnet@ncsu.edu Calvin Mordy , calvin.w.mordy@noaa.gov, CICOES, University of Washington Phyllis Stabeno , phyllis.stabeno@noaa.gov, NOAA Pacific Marine Environmental Laboratory Size structure of phytoplankton populations has been shown to be an important determinant of the flow of carbon and energy to higher trophic levels in Arctic ecosystems. Phytoplankton populations dominated by small (<10um) pico- and nanophytoplankton cells are generally dominated by eukaryotic flagellates that are tightly grazed by microzooplankton leading to increases in trophic length and limited transfer to higher trophic levels. Furthermore, general observations suggests that the picocyanobacteria Synechococcus is detectable but comprises a negligible fraction of phytoplankton carbon in Arctic ecosystems. As part of the Arctic IERP sampling program, we quantified the abundance of the Synechococcus , and other picophytoplankton, during the spring to fall period between 2017-2019 in the Northern Bering and Chukchi Seas. Synechococcus abundances increased from <500 cells/ml in spring to >50,000 cells/ml in the fall around Kotzebue Sound. Furthermore, the spatial extent of regions with elevated Synecococcus abundances in late summer/fall, as well as the absolute abundances, increased from 2017 to 2019, coincident with increasing late summer/fall water temperatures. The ratio of Synechococcus to diatom biomass was linearly related to average mixed layer temperature and increased to values exceeding 10:1 in the summer/fall of 2019. Analysis of previously collected Synechococus abundance data in the Chukchi Sea further supports a broader trend of increasing abundance in response to a warming Chukchi Sea, and the increased importance of a previously marginal phytoplankton group. The full implications of these changes in the phytoplankton community remain to be resolved.
Alaska Marine Science Symposium 2023 67
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