D. Petrova*, D. Gerdzhikov
Institute of Fish Resources, 4 Primorski, 9000 Varna, Bulgaria
Abstract. The aim of this paper was to study and assess the quality of Bulgarian Black Sea coastal water using the biological quality element phytoplankton communities, according to the requirements of the Water Framework Directive (WFD EU, 2000) and the developed reference values. A total of 134 species of microalgae were identified among which dominated the complex Bacillariophyceae/Dinophyceae (72.39 %). There was an improvement of the ecological status in three to six points from September to November 2011 (Krapetz, Shabla, Kamchiya, Dvoynitsa, Nessebar, Sozopol). This was due to the better characteristics of the phytoplankton community referring to Shannon index, number of species, Sheldon index, %MEC, DE% and Chl-a. Phytoplankton blooms were recorded in Krapetz, Varvara and Nessebar in September and in Albena, Varna-North, Sarafovo and Rosenets in November. Studies conducted have contributed to contemporary assessment of the water status in the one-mile area within the National Environmental Monitoring System (NEMS).