Phytoplankton data collected by the IBSS staff on the R/V Knipovich in the Black Sea along the Yalta-Batumi transect during the cruise in August-September 1948, and along the Yalta - Sukhumi transect, diurnal station 8, 50 km from Sukhumi in April 1950. This dataset contains abundance data (individuals per liter) for phytoplankton taxa collected in layer and discrete depths samples. Biomass data (mg/m³) are also available for 1948. No additional metadata is available.