Dataset includes phytoplankton data collected during cruise 25 of R/V Skif (January 1990) in the Indian sector of the Southern Ocean. Samples were taken by 7 L Niskin bathometer at standard depths: 0, 10, 25, 30, 50, and 100 m. Samples were concentrated by reverse filtration through nucleoporous (nuclear) filters with 1 µm size pores. Fixation - 40% formaldehid or glutar. Cell counts were done with a light microscope (magnification 100, 200, 400 x). Individual biovolumes and biomass (wet weight) were calculated via geometric approximations. At IBSS, the data were digitized from paper processing books, quality-controlled and transformed to comply with the Darwin Core/OBIS Schema. Funds for data operations were kindly provided by the Census of Marine Life International Cosmos Prize Fund, through a grant to Rutgers University.