10. Seasonal Changes of Hydrobiological and Bio-Optical Parameters in the Coastal Areas of the Western Part of the Black Sea

Study of the Black Sea neritic ecosystem is of great theoretical and practical significance owing to the anthropogenic load on its coastal areas. Variability of the ecological condition of these areas can be defined by the results of studying spatial-temporal variability of the nutrients and the suspended organic matter (SOM) content distributions. Such studies permit to assess the marine ecosystem productivity, intensity of biochemical processes, and flexibility of this ecosystem to the impact of various natural and anthropogenic factors. In recent decades, along with the expeditionary studies, satellite observations of the marine environment bio-optical parameters obtained by color scanners became widely used. Such kind of observations allows obtaining qualitatively new (as for its spatial-temporal characteristics) information. Based on the multi-year (1979–1995) expeditionary observations of distribution of the SOM components’ concentration and the bio-optical parameters (chlorophyll a concentration, light absorption and scattering indices) resulted from the satellite data (SeaWiFS, MODIS, 1997–2015), considered are the peculiarities of spatial-temporal variability of their distribution in the shelf areas of the western Black Sea. The degree of the effect of the riverine discharge and the open sea water masses upon the distribution of the parameters under study in the northwestern part of the sea makes it possible to define four areas (western, northern, central and eastern), and in the coastal zone of the western part – the Romanian and the Bulgarian ones. The statistical assessments of seasonal variations of the considered indices are obtained for these areas. Increase of the SOM components’ concentrations in the summer-autumn period in late 1980s and early 1990s with their anomalously high values in 1992 is noted. It is shown that the seasonal interannual variability in the concentrations of the SOM components and the values of the bio-optical parameters is conditioned by the variations in the riverine discharge volume, its run to the sea, and climatic shifts.