(Table 1) Abundance of bacterioplankton and cyanobacteria in waters of the East Atlantic and Mediterranean Sea

Distribution of cyanobacteria as compared with total bacterioplankton was studied in the Mediterranean Sea and off the west coast of Africa in November 1985 - January 1986. Fluorescent microscopy indicated that abund¬ance of chroococcoid cyanobacteria was 2 to 3 orders of magnitude lower than that of non-fluorescent bacteria. Cyanobacteria cells were larger than other bacterial cells and had in average 4 times larger volume. Biomass of cyanobacteria was significant percentage (5-15%) of total bacterioplankton biomass only in the surface interval (0-30 m).