This project will measure the rates of carbon uptake through the process of calcification and photosynthesis during one of the JGOFS cruises in the equatorial Pacific. The overwhelming contribution of calcite to the sediments of the eastern equatorial Pacific has long been realized (70-90% of the total sediment mass is calcite, and less than 1% is organic). Moreover, half of this calcite is produced from the calcified plates of coccolithophorid phytoplankters which are called coccoliths. Using published data on accumulation rates in the equatorial pacific region and conservative assumptions about the ratio of biologically fixed calcite which is ultimately buried, it can be argued that calcification is at least of equal magnitude to new production in the eastern tropical Pacific. In terms of the carbon which is ultimately buried on a yearly time scale, calcite dominated the carbon flux while most of the organic material is re-oxidized to carbon dioxide (CO2) within the water column. This project will document the magnitude of the surface calcification signal along with the standard photosynthesis measurements. Simulated-in-situ measurements will be performed of both calcification and photosynthesis. The data will be compared with the sediment trap data as a cross-check of the sediment- trap-derived accumulation rates; in a region such as the equatorial Pacific, which is known for its large current shears, this verification is essential. The data will also represent some of the first direct measurements of surface calcification in the equatorial Pacific and will be of significant interest and use to both biologists and geologists.
