This proposal award will serve as a companion project to the "EDDIES" (EDDY Dynamics, mixing Export, and Species composition) project funded by NSF Biological, Chemical and Physical Oceanography. This interdisciplinary field program will be initiated in the Sargasso Sea during the summer of 2004 and 2005. Recent evidence suggests that mesoscale eddies are an important nutrient transport mechanism in the oligotrophic waters of the main subtropical gyres. Numerical simulations and satellite-based statistical estimates indicate that the magnitude of the eddy-driven nutrient flux could be sufficient to balance geochemical estimates of new production. Relatively few direct observations of this process are available, owing to the spatial and temporal intermittency of the events that drive it. Available data demonstrate that isopycnal displacements associated with certain types of eddies can transport nutrients into the euphotic zone, resulting in the accumulation of chlorophyll in overlying waters. Preliminary data, included in this proposal, indicate that coincident with the passage of a cyclonic eddy at the BATS site, bacterial production rates were significantly enhanced relative to the monthly mean values. However, the extent of the prokaryotic heterotrophic response and their impact on coupled biogeochemical cycles and export has yet to be elucidated. This companion project proposes to sample parameters relevant to heterotrophic prokaryotes across mesoscale eddies documenting how these parameters vary inside the eddy through time and space (horizontal and vertical) relative to outside (.control.) waters. Specifically the PIs propose to: 1. Assess the spatial and temporal variability of prokaryotic biomass and production rates in response to eddy induced nutrient pumping by comparing stocks and rates throughout the surface 700 m, in and out of the mesoscale feature. 2. Determine if a mesoscale eddy perturbation and subsequent nutrient pumping affects the bioavailability of newly produced dissolved organic matter (DOM) and the efficiency with which the prokaryotic community processes it. 3. Assess how eddy induced nutrient pumping may affect the partitioning of attached versus free-living microbial processes. 4. Determine if the mesoscale perturbation and the resulting changes in biogeochemistry lead to a change in the prokaryotic community structure. Intellectual Merit Compilation of these measurements will provide a rigorous assessment of the response of heterotrophic prokaryotes to the organic matter regime of the eddy bloom environment. Prokaryotes play an important role in determining the biogeochemical fate of a bloom. The oligotrophic waters of subtropical gyres are typically characterized by extensive recycling of elements through the microbial loop with little export. As biology responds to the eddy-induced nutrient pumping it will be important to document the rate and efficiency by which heterotrophic prokaryotes process freshly produced organic matter in order to better understand the flow of carbon and energy in these mesoscale features. Monitoring the prokaryotic community structure will be important to gain insight to the ecological response and biogeochemical processing within these features. Our measurements will complement and strengthen concurrent assessments of various parameters collected by the funded EDDIES program. Broader Impacts There are four specific objectives incorporated into the broader impacts portion of this proposal: 1) Participation and support for a post-doctoral fellow as well as undergraduate laboratory assistants, 2) Curricular development at UCSB, 3) Web-based outreach programs integrating the microbial data set into a centralized .EDDIES. website, the BATS and Microbial Observatories websites as well as the UCSB Marine Science Institute web- and laboratory-based outreach programs, and 4) Integration of fieldwork at sea experiences into the UCSB Women in Science and Engineering (WISE) mentorship program targeted at keeping undergraduate women in the sciences.
