RESUMO

Data on the rate of the uptake of inorganic phosphorus by microplankton and its turnover time in the upper 50 m layer of water of the Black Sea registered in August-September 1990 are presented. A high rate of the uptake of phosphate (on the average 180·10^-4 mM P·year^-1) and a short time of their turnover (on the average 0.9 year) are characteristic of the upper 10-15 m layer of water characterized by a low content of phosphate. Their low content suggests that the process of regeneration is the main source of phosphorus taken up by microplankton in the surface layer of water of the Black Sea in summertime. It has been found that the difference in the rate of the uptake of phosphorus by microplankton in various sections of the sea is conditioned by their trophic level. The content of phytoplankton (in terms of chlorophyll a concentration) is the main factor responsible for the rate of phosphorus uptake in the deep-water section, and also in the northwestern part of the sea.