PHYSIOLOGICAL AND ECOSYSTEM STRUCTURE FORCINGS ON CARBON FLUXES IN THE SOUTHERN OCEAN MIXED LAYER

Duke University, Durham NC

Investigators

Abstract

Based on underway measurements of the dissolved O2/Ar ratio and the triple isotopic (16O,17O, 18O) composition of oxygen in surface seawater samples, estimates of two non-incubation biogeochemical proxies are to be determined on cruises in the LTER study region adjacent to Palmer Station. A measure of biological produced oxygen super-saturation can be made from the O2/Ar ratio. A separate triple isotopic determination of dissolved oxygen yields the fraction of the dissolved oxygen pool derived from phytoplankton photosynthesis. Along with a knowledge of the oxygen gas exchange coefficient, rates of net community production (NCP) and gross primary production (GPP) in the mixed layer can be estimated. Other biogeochemical parameters such as nutrients, light, mesoscale variability, pulse amplitude fluorescence (indication of phytoplankton physiological stress), plankton taxonomy (HPLC pigments; satellite imagery), along with particulate organic carbon may be used to interpret and synthesize the biological productivity terms. Study of the Southern Ocean oxygen cycle allows a complementary view of the carbon cycle to be constructed, and in principle may serve as an independent check of the carbon budget terms in this important CO2 sink region of the global ocean. Secondly, the potential for ecosystem change may also be revealed from study of the relationships between proxies of net community production and the assemblage of Southern Ocean plankton communities.