Seasonal dynamics of the species composition, numbers, and biomass of phytoplankton occurring in sedimentation traps exposed from June 1995 till May 1996 at a depth of 4.5 m on the bottom of Kazachya Bay of the Black Sea are considered. The duration of exposure was 15-20 days. The contents of traps were studied separately in two fractions: in the suspension of bottom sediments and in the near-bottom layer of water. A total of 131 taxa of microalgae belonging to Bacillariophyta (95 taxa), Dinophyta (25), Chrysophyta (8), Cryptophyta (2), and Cynophyta (1) were found during the period of investigations. In this case, 63 taxa were found in the near-bottom layer of water, 89 taxa in the suspension of bottom sediments, and 21 taxa in both fractions. Bacillariophyta (about 73 %) prevailed in terms of the number of their species in bottom sediments, whereas Dinophyta (19 %) dominated in water column. During the process of sedimentation, more than 40 % of the total number of species remained in water column, whereas about 60 % of their species were registered in bottom sediments. [ABSTRACT FROM AUTHOR]