SGER: Elemental Ratio Anomalies Associated with Antarctic Marine Phytoplankton

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AbstractOPP-0108759P.I. Michael LizotteRecent cruises to the Ross Sea under the JGOFS and ROAVERRS programs have documented that the removal of dissolved carbon and nutrients can be significantly different from the ratios predicted from typical Redfield ratios (e.g. 106:16:1 for C:N:P) for seawater particulates. The non-Redfield nutrient removal ratios were associated with phytoplankton species composition. For example, C:N:P uptake ratios determined from measurements of dissolved inorganic carbon, nitrate and phosphate were ca. 80:10:1 in diatom-dominated stations and ca. 140:20:1 for Phaeocystis antarctica-dominated stations. Non-Redfield dynamics could be critical for understanding the biogeochemistry of the geological record as well as predicting the impacts of climate change. Samples are to be collected from a ship of opportunity during a geophysics cruise (NBP 01-01, Hobart to Capetown) to the Indian Ocean sector of the Southern Ocean. Species composition will be quantified by microscopy from preserved water samples. Nutrient concentrations (nitrate, nitrite, phosphate, and silicate) will be measured from frozen sampled collected in conjunction with water a sampling program that is to be conducted to study carbon dynamics. These "samples of opportunity" will provide a data set to be used in evaluating whether the non-Redfield situation observed in the Ross Sea occurs in distant coastal systems around Antarctica, and whether it is associated with the same species or similar oceanographic conditions.