Collaborative Research: The effect of carbonate chemistry on the sea ice community in the High Arctic

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Sea ice influences many physical, atmospheric, chemical and biological processes occurring in the Arctic. Sea ice is also a challenging habitat to assess: it moves in response to wind, and hence nearly always moves independently of surface waters. The properties of the ice, which influence a suite of chemical and biological interactions between the atmosphere, the ice, and the surface ocean, change over both space and time. While enhanced photosynthesis is expected in the increasingly ice-free Arctic Ocean, there has been little research to determine the impact of increased atmospheric carbon dioxide (CO2) and other environmental changes on the microbes that grow within and beneath the sea ice. This research will contribute to our understanding of elemental cycles in the central Arctic basin and of the vulnerability of the sea ice biological community to a rapidly changing environment, particularly as it is impacted by increasing carbon dioxide concentrations and ocean acidification. The project is part of a joint US-Swedish collaboration and will support an early-career female faculty member. It will also support the training of a graduate student and a postdoctoral scientist who will gain experience with underway and discrete biogeochemical sampling as well as incubation experiments. The investigators will conduct public outreach about changes in the Arctic Ocean at the VIMS Marine Science Day and Polar Science Weekend at the Pacific Science Center in Seattle. The overall objective of this research is to assess how changes in seawater chemistry as a result of increases in atmospheric carbon dioxide (CO2) will alter algal-bacterial interactions in sea ice. Recent losses of Arctic sea ice have resulted in an increased uptake of atmospheric CO2, accelerating the rate of acidification in a region that is rapidly changing. While enhanced marine productivity is expected in an increasingly ice-free Arctic, the impact of the changing environment on ice-dependent biological communities is challenging to predict. As part of a joint US-Swedish collaboration, this work will provide a quantitative assessment of the sensitivity of ice-dependent algae and bacteria to changes in pH and use a combination of underway and discrete sampling to deliver new observations on the spatial and temporal variability of the CO2 system in the High Arctic in late summer when sea ice is at a minimum. In addition, the research team will perform a suite of ship-board experiments that manipulate seawater pH to assess the impacts on sea ice biota and their exopolymer polysaccharide products. Although previous work has focused on the impact of elevated CO2 on phytoplankton, there has been little targeted research on ice-dependent biota. Given the paucity of CO2 system observations in the central Arctic basin, especially late in the productive season when the impact of autumn production and the seasonal salinity minimum can be included in the cumulative estimate of production, the observations proposed here will be of particular significance.