Using long-term observational data on beam attenuation coefficient (BAC) and depth of visibility of Secchi Disk, the main peculiarities of annual cycle of transparency distribution in surface water layer of the north-western Black Sea were considered. Statistical estimations of seasonal and intra-seasonal variations of BAC in the areas which differ in the degree of influence on their hydrophysical characteristics of river and open-sea water flow were obtained, and their good agreement with variations of content of suspended matter components was noted. Seasonal values of BAC on chlorophyll a concentration were calculated, based on the use of regressive dependence between these parameters being measured simultaneously. It is shown that long-term (1978-2010) seasonal variations of BAC (measured and calculated) and, connected with them, variations of chlorophyll a concentration depend on variability of the river flow capacity, coverage of its distribution on the north western shelf and regional hydrometeorological conditions.
beam attenuation coefficient, chlorophyll a, river run-off, hydrometeorological conditions, variability