Further Calibration of Long-Chain Alkenones for Paleoceanographic Study

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Long-chain alkenones are now widely recognized as promising for the assessment of paleotemperature and to some extent paleoproductivity in surface waters of the ocean. Ourability to interpret accurately the complete paleoceanographic implications of stratigraphic records for the alkenones inmarine sediment cores is currently limited by an ignorance of the ecology of the phytoplankton species that produce these biomarkers and of the ecology of the phytoplankton species that produce these biomarkers and of the processes responsible for their preservation in the sedimentary record. This research will advance our ability to extract realistice paleoceanographic information from the sedimentary record for the alkenonoes. The project willintegrate results from analyses of laboratory phytoplankton cultures and particulate samples from the field. The field samples include select sets of suspended particulate materials collected from ocean surface waters, vertically transported particulate materials collected in time series by sediment traps and underlying sediments collected by coring at three locations along an east-west transect off northern California. The two major goals of the proposed work are to clarify 1) where alkenone-producing phytoplankton reside withing the euphotic zone as a function of season, when these organisms are productive during the year and what surface water temperature is recorded by alkenone unsaturation patterns measured in underlying sediments as a consequence of these factors and 2) how the downcore record for alkenone concentration relates torelative changes in prymnesiophyte productivity and perhaps total primary productivity in overlying waters with time.