DISTRIBUTION OF CO2 SPECIES, ESTIMATES OF NET COMMUNITY PRODUCTION, AND AIR-SEA CO2 EXCHANGE IN THE ROSS SEA POLYNYA

Measurements of surface total carbon dioxide (TCO2), alkalinity, and c alculated pCO(2), along with water column nutrients and hydrography, w ere made on two cruises to the Ross Sea polynya (NBP 94-6, November-De cember 1994 and NBP 95-8, December 1995 to January 1996). The polynya experiences an intense phytoplankton bloom during a Short period of op en water conditions from mid-December to mid-February each year. Our b iogeochemical observations were used to determine the temporal variabi lity of CO2, fluxes of carbon within the ocean, and rates of air-sea e xchange of CO2. Depletions of TCO2, pCO(2), and nitrate+nitrite were c onsiderable (similar to 70-150 mu mol kg 80-150 mu atm, and 10-20 mu m ol kg(-1), respectively) and associated primarily with biological upta ke during Phaeocystis and diatom blooms. Alkalinity was a conservative tracer bf salinity and nitrate+nitrite. Surface pCO(2) was undersatur ated by similar to 50-150 mu atm, and air-sea gas exchange of CO2 duri ng open water conditions was directed from atmosphere to ocean. Observ ed surface stoichiometric C:N ratios were 6.66: 1 and 6.77:1 for the 2 years, consistent with global ''Redfield'' ratios, while C:P and N:P ratios were variable (75-141:1, 12-18:1). Estimates of net community p roduction (NCP) rates were made using in situ changes in TCO2 and nitr ate+nitrite across repeated transects along 76 degrees 30'S. Mean NCP rates across the polynya ranged from 0.86 to 0.98 g C m(-2) d(-1). The se values may be underestimated by 5-25% because of the contribution o f atmospheric CO2 to the surface layer through gas exchange. Export of carbon from the surface to depth was at least 55-60% of NCP rates.