HR: 10:50h
AN: OS32A-03    [Abstracts]
TI: Biogeochemical Fluxes of Carbon and Nitrogen in Surface Waters of the Cariaco Basin: A Combined Rate Measurement and Isotopic Approach
AU: Muller-Karger, F E
EM: carib@marine.usf.edu
AF: University of South Florida, 140 7th Ave. South, St. Petersburg, FL 33701 United States
AU: * Sambrotto, R N
EM: sambrott@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, 61 Rt. 9W, Palisades, NY 10964 United States
AB: As a tropical ocean margin influenced by seasonal upwelling, the plankton productivity of the Cariaco Basin varies greatly between some of the largest rates measured in ocean waters, to near oligotrophic conditions, over the course of a year. The fluxes of carbon and nitrogen associated with these biological variations also change significantly and will be analyzed in the context of a consistent time series of physical, chemical and biological data collected monthly over the last several years. New (nitrate) productivity increases in response to the upwelling of nutrients in winter and also to a secondary (although somewhat smaller) upwelling period in summer. There appears to be significant regenerated nutrients (such as ammonium and dissolved organic matter) to fuel production at other times of the year as well. As an additional dimension in the analysis of carbon and nitrogen flow, the isotopic signatures of the zooplankton collected in net hauls were examined over a two-year period. The C-13/C-12 ratio of the zooplankton pool was significantly heavier in the winter upwelling season, but showed little response to summer upwelling. The N-15/N-14 ratio, on the other hand, increased in both upwelling periods and also exhibited a two-year trend towards higher values. These variations are potentially a rich source of information on the dynamics of the epipelagic environment and likely reflect in part, the lower pCO2 levels and larger phytoplankton cells in the winter upwelling season, as well as the intrusion of nitrate from outside of the basin during both the winter and summer upwelling periods.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4817 Food chains
DE: 4845 Nutrients and nutrient cycling
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting