Variability of Particulate Organic Phosphorus in the Northwestern Part of the Black Sea

Based on long-term (1985–1995) monitoring data, the paper considers the peculiarities of seasonal variability in the spatial and vertical distribution of particulate organic phosphorus (РPOM) in the surface layer and in the photosynthetic zone in the northwestern Black Sea. Regression equations, experimental data, and satellite observations for the chlorophyll a concentration allowed us to evaluate the seasonal longterm (1979–1995) variability in РPOM in the surface layer and photosynthesis zone. The ratios of the concentrations of particulate organic carbon, nitrogen, phosphorus, and chlorophyll a are calculated and statistical estimates of seasonal changes in the РPOM in the areas with different degrees of influence of river runoff and water of open seas are obtained. The consistency of intra-annual changes in the concentrations of РPOM, chlorophyll a, and phytoplankton biomass is shown, which indicates the role of phytoplankton in the formation of РPOM and in its intra- and interannual variability in the northwestern part of the sea. It is shown that long-term seasonal variations in РPOM and related changes in the concentration of chlorophyll a depend on the variability of bulk river runoff, the extent of its abundance in the northwestern shelf, and regional hydrometeorological conditions.