Sediment oxygen consumption in the Pacific Arctic: Impacts of increased temperature and food supply on the benthic community and individual dominant organisms

Temperature and food supply influence benthic community structure, with food acting as one of the largest drivers for benthic biomass, including for dominant bivalve species (e.g. Macoma calcarea) that are important components of the benthic food web. The Pacific Arctic, particularly the northern Bering Sea in recent years, has experienced rapid environmental change, with shifts to shorter seasonal sea ice duration and significantly higher surface and bottom water temperatures. Understanding biological responses to changing temperatures and food availability is crucial for evaluating ecosystem change. Sediment community oxygen consumption (SCOC) incubation experiments were undertaken shipboard on the US Coast Guard Cutter Healy during the summer of 2019 in order to examine the effects of increased temperatures and food addition to overall community oxygen consumption and nutrient cycling in the northern Bering and Chukchi Seas. These experiments, part of activities associated with the Distributed Biological Observatory (DBO) - Northern Chukchi Integrated Study, were completed at six sites in the DBO1 (northern Bering Sea), DBO3 (SE Chukchi Sea), and DBO4 (NE Chukchi Sea) regions on a latitudinal gradient. Our initial findings indicate SCOC is higher in warmer temperatures and usually higher with the addition of food, which is generally consistent with previous experimental results in this region. Respiration rates were also evaluated for individual specimens of dominant benthic organisms at each site, primarily different species of bivalves (Macoma calcarea and Ennucula tenuis) and the amphipod (Ampelisca sp.) at a station in the northeast Chukchi Sea. Individual metabolic rates of these organisms are compared to total oxygen consumption rates in the full sediment cores and ammonium flux rates as an indicator of excretion.