Structure of phytoplankton communities in Kaliakra protected area, summer 2020 – 2021

Abstract. Marine protected area (MPA) Kaliakra is an object of interest owning to its geographic location, the peculiarity of the hydrodynamic processes and the influence of the river inflow into the North - West part of the basin. The analysis of phytoplankton in the area of Cape Kaliakra was based on 20 samples from 16 stations in coastal waters in the summer of 2020 and 2021. The aim of this study was to make a recent assessment of the phytoplankton communities in MPA Kaliakra and to analyze the phytoplankton changes compared to previous years. The received results showed high species diversity (88 species of microalgae, 13 taxonomic classes) and development of stable phytoplankton communities. Increased abundance and biomass of phytoplankton and amounts of nutrients in the summer of 2020-2021 in the protected area of Kaliakra demonstrated degraded water quality. In 2020, the small-sized species Merismopedia sp. and small Flagellates were recorded in blooms, while in 2021 phytoplankton blooms were not recorded.