Latitudinal fluctuations in density and biomass of heterotrophic bacterioplankton from Antarctic Peninsula to Argentine shelf waters.

FRANZOSI, C.A.; LARA, R.J.; KATTNER, G.; ALDER, V.

Buenos Aires

Conferencia; SCAR XXXI & Open Science Conference; 2010

This study describes the changes in density and biomass of heterotrophic bacteria along a latitudinal gradient as related to different biogeochemical variables (dissolved organic carbon and nitrogen, ammonia, nitrite, nitrate, phosphate), total chlorophyll, and the density of heterotrophic nanoflagellates. The analysis was based on sub-surface samples (9m depth) collected during the end of summer ? beginning of autumn 2005 at 38 oceanographic stations established between Antarctic Peninsula and the Argentine shelf (38º-68º S). Bacterioplanktonic density and biomass correlated positively with each other and with DOC and temperature, while negatively with phosphate and the dissolved inorganic nitrogen species. In addition, positive correlations were found for biomass vs. DON and chlorophyll, and for density vs. heterotrophic nanoflagellate biomass. Mean abundance values recorded in waters off Antarctic Peninsula (5.8x105 cells mL-1; 14 µgC L-1) were quite similar to those of the Drake Passage (4.4x105 cells mL-1; 11 µgC L-1). These two regions, instead, showed values significantly lower than those estimated for the subantarctic waters of the Argentine shelf (1.6x106 cells mL-1; 32 µgC L-1). The results obtained suggest that the density of heterotrophic bacteria within the latter region is controlled by nitrogen concentration in its northern sector and by consumption by nanoflagellates in its middle part.