Roles of Heterotrophic Bacteria and Protists in the Arctic Ocean Carbon Cycle

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9400218 Sherr Research supported by this grant is under the auspices of the Arctic Systems Science (ARCSS) Global Change Research Program and is jointly sponsored by the Division of Ocean Sciences and the Office of Polar Programs. The research will be centered around a unique and intensive, multidisciplinary research expedition to parts of the Arctic Ocean that have never been extensively studied. The 1994 U.S./Canada Arctic Ocean Section is a collaborative effort with Canada that will involve approximately 60 scientists on a Canadian and a U.S. icebreaker during summer 1994. NSF-funded projects will focus on hydrography, biology, paleo-, and sea-ice studies. Data collected will be amongst the first ever from several regions of the Arctic Ocean and will be highly relevant to improving our understanding of how the Arctic is an indicator of changing global climate conditions and how it affects the physical, chemical, and biological features of the more temperate oceans and regions. This collaborative research effort between investigators at Oregon State University and the University of Delaware represents a critical component of the AOS biology program. Research will measure microzooplankton abundances, biomass, and size distributions, together with estimates of their grazing on phytoplankton and other zooplankton. Work will focus on heterotrophic bacteria and protists in the water column and sea ice of the Arctic Ocean. Present information is sparse on the abundance and activity of these microbes and about their influence on primary production. The investigators will quantify the distribution of numbers, biomass, and productivity of bacteria and compare these parameters to the in situ concentrations of labile organic substrates (dissolved free + combined amino acids and sugars); quantify the abundance, size frequency distribution, and biomass of phagotrophic protists in the nano- and microplankton size classes; and measure the grazing impact of protists on bacteria and on algal cells . Incubation experiments will also be performed where substrate concentrations and temperatures are varied to ascertain the effect on heterotrophic bacterial growth. Understanding these processes will help resolve role heterotrophic and autotrophic microbes' influence on the Arctic carbon cycle. ***