During the austral summer 2004, an intensive multidisciplinary survey was carried out in the Indian Ocean sector of the Southern Ocean to study the main hydrographic features and the associated productivity processes. This sector includes circumpolar zones and fronts with distinct hydrographic and trophic regimes, such as the Subtropical Zone, Subtropical Frontal Zone, Sub Antarctic Zone, Polar Frontal Zone, Northern Subtropical Front , Agulhas Retroflection Front, Southern Subtropical Front, Subantarctic Front, Surface Polar Front, and SubSurface Polar Front. Seasonal variations in the solar irradiance and day length, stratification, lack of micronutrients like iron and increased grazing pressure are the major factors that influenced or constrained biological production in this region. Even though there are broad differences in these controlling factors in time and space between the zonal regions, the upper 1000 m of the water column of the main zones viz. (STZ, STFZ, SAZ, PFZ) supported almost identical standing stocks of mesozooplankton (0.43, 0.47, 0.45 and 0.49 ml m-3, respectively) during the austral summer. This unexpected similarity can be explained either through the functioning of the microbial loop within STZ,STFZ and SAZ or the multivorous foodweb ecology within the PFZ. Dominance of ciliates in the microzooplankton community may be one facor resulting in the maintenance of a high mesozooplankton standing stock in SAZ. In contrast to the zones, frontal regions showed wide differences in hydrography and biological characteristics. The SSTF and SPF were far more biologically productive than that of NSTF and ARF