Photo-Ecological Investigations of Phytoplankton of the Central Equatorial Pacific Ocean (JGOFS)

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A major goal of the U.S. JGOFS program is to quantify the role of the equatorial Pacific in global biogeochemical fluxes. Quasi- stationary upwelling of nitrate-rich water within this extensive oceanic regime stimulates primary productivity and can lead to localized phytoplankton biomass accumulations. The atmospheric and physical forcings which regulate phytoplankton production are complex and variable and lead to large spatio-temporal variations in carbon fixation rates and phytoplankton standing stocks. Accurate resolution of phytoplankton processes will require sampling on appropriate time and space scales as well as an understanding of hydrodynamical forces. Toward this objective the P.I. propose to (1) provide core measurements of algal pigments (chlorophylls, carotenoids, phycobilins and phaeopigments) during the two survey cruises (fall and spring) and the 1992 spring time-series cruise; and (2) conduct photo- ecological investigations of phytoplankton. Analytical analyses will employ QA/QC procedures to insure highly accurate and precise, as well as 'comparable' data. Photo-ecological studies will incorporate core pigment data to (A) infer seasonal, spatial and depth-dependent variations in phytoplankton biomass and composition; (B) estimate rates of vertical mixing of phytoplankton; and (C) bio-optically model depth-dependent rates of primary production from shipboard and moored platforms.