Mesozooplankton-microbial Food Web Interactions in a Climatically Changing Sea Ice Environment

Funds are provided for an analysis of the impact of changing sea ice conditions on planktonic food web structure, focusing on microzooplankton and mesozooplankton trophic linkages and the fate of phytoplankton blooms in the Bering Sea during spring sea ice conditions. To this end, the principal investigators plan to conduct experiments over a range of ice, ice edge, and open water conditions, and, particularly, will consider the importance of detached ice algae, when present, as a food source for the secondary consumers. As part of this effort, they will determine standing stock biomass, composition, and size structures of phytoplankton, microzooplankton and mesozooplankton assemblages, measure microzooplankton growth and mesozooplankton reproduction rates, and measure grazing rates and prey preferences of heterotrophic protists and dominant species of mesozooplankton. They will also determine the fine scale vertical distribution of plankton, especially of fragile forms such as colonial phytoplankton, to identify thin layers of plankton/ particles in association with hydrographic features. Their collaborative study will explicitly address trophic linkages previously unexplored in this region of the subarctic. They hypothesize that changing ecosystem structure due to global warming, e.g. decrease in seasonal sea ice, will alter these trophic interactions, and thus the ultimate fates of algal production in this region. They plan to participate in each of the three annual cruises proposed for spring sea-ice conditions during the BEST field program. They will carry out a full set of analyses (standing stock determinations and rate measurements) at designated stations along transects within the BEST study area. Abundances and rate measures will be combined to determine relative microzooplankton and mesozooplankton grazing impacts.

While the direct measurements and observations to be derived from this program will allow the principal investigators to describe the microzooplankton and mesozooplankton of the eastern Bering Sea shelf and their grazing impacts with a detail heretofore unavailable, the numbers they derive will also provide strong constraints on the ecosystem models to be developed as part of BEST. These models will serve as an important tool during the synthesis of the collective understanding derived by the BEST investigators.