Biogeographic distributions of Ostracoda in the Bering, Chukchi and Beaufort Seas

The distribution of benthic marine ostracodes (Crustacea) from Arctic and subarctic continental shelves of the Bering, Chukchi and Beaufort Seas was evaluated to determine if an ecosystem “regime shift” can be detected from geographic changes in ecologically sensitive species during the last 48 years. More than 800 surface sediment samples (0-2cm) containing >100,000 ostracode specimens were quantitatively analyzed to assess recent changes in benthic meiofaunal communities from 1970 to 2018. Samples contain a mixture of Arctic, subarctic and cold-temperate taxa. Ostracode species distributions are related to environmental parameters (e.g. temperature, salinity, sediment grain size, total organic carbon, total organic nitrogen, carbon/nitrogen ratios, and sediment chlorophyll), which are used to provide insight into conditions that control the distribution and abundance of benthic taxa within the study area. Results suggest that subarctic and cold temperate species are increasing in relative abundance in the study area, particularly in the southern Chukchi Sea, since 2010--a period that marks significant and continued decline in sea ice persistence. Since that time, species such as Elofsonella concinna, Hemicytherura clathrata, Kotoracythere arctoborealis, Munseyella kiklukhensis, Schizocythere ikeyai, and Semicytherura spp.), which inhabit North Pacific regions off Asia and in the Bering Sea, occur in greater proportions in the Chukchi and Beaufort Seas. This presentation will include time-series results and variability in ostracode assemblages in the Pacific Arctic in relation to changing environmental conditions.