Southern Ocean, Indian sector

Bacteria generic abundance in water bodies; Zooplankton carbon biomass per unit area of the water column; Bacterial production in the water column; Microzooplankton taxonomy-related biomass expressed as carbon per unit volume of the water column; Microzooplankton taxonomic abundance in water bodies

Discrete water samplers; optical microscopes; fluorescence microscopes; shipboard incubators

Distribution of bacterioplankton and protozoa in the upper water column along the transect 62 degrees east in the Indian sector of the Southern Ocean was determined during the ANTARES 2 cruise in austral autumn 1994. The transect 62 degrees east crosses several water masses from the Antarctic Divergence (southernmost stations) to the Subtropical Convergence (northernmost stations). Bacterioplankton biomass and production, composition of bacterioplankton communities and protozoan (flagellates and ciliates) numbers were determined from 6 depths from the vertical profile of the upper 200 m water column. Over tenfold range of bacterioplankton production and cell numbers were recorded along the transect 62 degrees east with highest values in the surface layer ( 0-100-m) and near to the ice at the southernmost station. High values were also recorded near to the Subtropical Convergence. Psychrophilic and psychrotrophic bacteria showed similar trend as bacterioplankton production with high values near to the ice and at the Subtropical Convergence, but the numbers were more evenly distributed throughout the upper water column (0-200m). Subsurface maximum was recorded with several measurements at both ends of the transect. The low bacterioplankton biomass and production rates recorded from 58-55 degrees south coincide with the low DOC recordings from the same water. Also the experimental studies performed with the low DOC water showed low growth rates and substantial stimulation of production rates by carbon enrichment.

Finnish Environment Institute
Latokartanonkaari 11
Helsinki

00790
Finland