COLLABORATIVE RESEARCH: What Controls the Transfer of Diatom Organic Matter to age-0 Pollock Prey in the Bering Sea Ecosystem?

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The highly productive and economically important Walleye Pollock commercial fishery of the Bering Sea depends on poorly understood food web pathways. Primary producers of organic carbon, notably diatoms, are consumed by large crustacean zooplankton, which, in turn, are consumed by juvenile pollock. The dominant paradigm for the system suggests that understanding changes in the biomass of large crustacean zooplankton can help estimate the survival of juvenile pollock; however, recent data show two orders of magnitude uncertainty in the carbon demand of large crustacean zooplankton. Such uncertainties impact the ability to manage the fishery. A revised model for the system has been proposed that involves consideration of both the quantity and quality of organic matter produced by diatoms and how this would constrain support for the commercial fishery. Before investing in a major field effort to test this approach, this project will assess the expected magnitude of change and associated errors, for diatom organic matter production, including the individual terms that are used to estimate it, i.e. abundance, growth rate, and cell carbon. This effort will be based on laboratory experiments and historical data analysis. The project will contribute to STEM workforce development through partial support for the training of a post-doctoral associate. Undergraduates would be entrained into the science through an REU program at Bigelow Laboratory for Ocean Sciences and through the Colby College Semester at Bigelow program. K-12 outreach will be facilitated through participation in the successful and long-standing Dauphin Island Sea Lab Discovery Hall program. Outreach to the general public will be accomplished through a blog, Bigelow?s Café Scientifique, and the Bigelow newsletter. The long-term goal for the research that this project would initiate is improved mechanistic and predictive models for commercial fisheries management.There is no consensus on the mechanistic relationship of where carbon from the lower trophic levels goes in the Bering Sea ecosystem, hence simple proportionality relationships between primary production and fisheries are used routinely. Bottom-up control on age-0 walleye pollock prey, i.e. large crustacean zooplankton (LCZ), could help constrain this coupling between the primary producers and pollock fishery, but there is a two-order-of-magnitude uncertainty in the LCZ carbon demand based on estimates from the Bering Sea Ecosystem Study (BEST). A new conceptual model is required and this project will begin to refine the issue by focusing on diatoms, which have a less patchy distribution than LCZ and are a key prey item of LCZ. A major knowledge gap exists in the understanding of the magnitude of diatom loss processes; the logical next step to understanding the fundamental linkage between primary production and fisheries in the eastern Bering Sea is to answer: what is the proportion of diatom primary production available for supporting higher trophic organisms and with which biogeochemical variables does this covary? Before testing this approach in a field setting, the expected magnitude of change and associated error for diatom organic matter production, including the individual terms that go into that estimate (i.e. abundance, growth rate, cell carbon), must be understood. This project will combine culture studies using diatoms isolated from high-latitude regions with literature and BEST program data to meet this initial objective.