Collaborative Research: The Role of Wind-Driven Transport in Shelf Productivity: Phytoplankton Size Spectra and the Fate of Upwelled Nutrients and CO2

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9910898DugdaleThis collaborative project, involving eleven investigators at five institutions is under the auspices of the Coastal Ocean Processes (CoOP) Program, and it focuses on the role of wind-driven transport in shelf productivity. Wind-driven continental shelves represent a paradox in that while they are characterized by high productivity due to upward fluxes of nutrients into the euphotic zone, wind forcing also represents negative physical and biological controls via offshore transport and deep (light-limiting) mixing of primary producers. Specifically, upwelling ecosystems along mid-latitude eastern boundaries of the ocean are well known for wind forcing and high productivity at lower trophic levels, with concomitant transport of near-surface plankton offshore. The group of researchers will conduct an interdisciplinary study to examine the roles that wind-driven transport plays in productivity over the shelf off northern California. Research will focus on key processes to explain the integrated functioning of highly productive planktonic systems over eastern boundary shelves in response to wind-driven transport, and specifically, to determine the sensitivity of these processes to both wind intensity and the time scales of wind forcing. Work will also identify specific features of the nutrient-phytoplankton-zooplankton (NPZ) food web that lead to greater or lesser secondary productivity in response to changes in wind forcing.To implement the study, part of the work will examine the 3-dimensional wind-driven circulation of water concurrently with size-structured distributions of phytoplankton and zooplankton species. Other efforts will study the key physical and biological processes that control primary production, zooplankton population responses, and offshore transport of plankton and nutrients over the strongly wind-driven shelf and slope off Bodega Bay. An integrated sampling scheme coupled with appropriate physical-biological models designed to synthesize and guide the fieldwork has been developed. The fieldwork will be comprised of fixed station time-series, ship surveys, drifter releases, and satellite remote sensing. There are two parts to the fieldwork - one focusing on the mooring array off Bodega Bay, and a second involving ship surveys and drifters. The mooring array places emphasis on eulerian measurements of cross-shelf circulation, aiming also to resolve up/downwelling fluxes. The surveys and drifters place emphasis on transformations in the water column, specifically the maturation of upwelled water as it moves away from the mooring site. By combining these data with the synoptic measurements available from satellites and the integrative aspects of the modeling, the project seeks to address all the important processes associated with wind-driven transport. This promises to unravel the paradox of how wind-driven transport supports high levels of productivity over eastern boundary shelf regions.This particular component of the study addresses questions about nutrient and pCO2 distributions and fluxes, about primary production and about phytoplankton distributions and fluxes. The objective is to determine the fate of nutrients, CO2 and phytoplankton productivity transported cross-margin over a strongly wind-driven shelf during upwelling and downwelling.