ИСТИНА

It was investigated the interannual and seasonal variability of phytoplankton in coastal north-eastern part of the Black Sea: species diversity, abundance and biomass depending on the variability of hydrological and hydrochemical conditions and pollution. Phytoplankton community was studied for more than 10 years as an example of Gelendzhik Bay. Interesting results were obtained by analyzing the species composition and biomass of phytoplankton, depending on the severity of the winters. In cold winter in 2008 year, flagellates algae Dinolagellatae were dominated in phytoplankton (81,4 %). In abnormally warm winter in 2009 year large diatoms were dominant in phytoplankton, the main part of whom were algae biomass Rhizosolenia calcar-avis (80%). Flagellates were presented Peridinium. Large diatoms and flagellates are more resistant to contamination. From 2009 year to 2011 year diatom algae Rhizosolenia calcar-avis was dominant in the phytoplankton community. This phenomenon is due to significantly of the nutrient substances concentration. With a decrease of the silicates concentration in the summer and winter 2012-2013 years biomass Rhizosolenia calcar-avis sharply decreased to natural values. This led to the restoration of the natural phytoplankton species composition of the Black Sea. Winter and summer 2014 year the rich silicates water came from the open sea. This fact again promoted mass flowering Rhizosolenia calcar-avis. Traditional for Black Sea species of algae Licmophora, Sceletonema, Peridinium in summer 2014 year were underrepresented. Quantitative development of diatom Rhizosolenia calcar-avis is a good indicator of natural conditions fluctuations in the coastal area of the north-eastern Black Sea and anthropogenic impacts on its ecosystem.