Phytoplankton samples were taken by bottles from different depths between 0 - 150 m with up to 15 replicates per depth horizon. Samples were concentrated by back filtration using nucleopore filters (D=1.5 µm). Samples were fixed by Lugol's solution and - after sample blooming - by 40% formaldehyde. After expedition samples were concentrated by siphon down to 2-10 ml volume. Calculations of phytoplankton cell numbers were made in 0.05 ml drop using a light microscope and then recalculated for 1 liter using a coefficient (as given in the data table). Biomasses of phytoplankton algae were calculated considering cells' volumes by equating real or average volumes of cells to corresponding geometric figures (Senichkina, L,1986, The calculation of cell volumes on diatoms using the coefficients at volumetric capacity, Hydrobiological Journal 22:56-59, in Russian).