Phytoplankton blooms in front of cape Galata (Black Sea) during the period 2008-2017

Abstract

Abstract. The aim of the study was to identify the peculiarities of the development of phytoplankton blooms (annual and seasonal dynamics) in front of cape Galata, Bulgarian Black Sea coast in the period 2008-2017. In that area up to 30 nautical miles (nm), from 6 stations (G-1, G-3, G-5, G-10, G-20 and G-30, respectively at 1, 3, 5, 10, 20 and 30 nm from the coast), 187 phytoplankton samples were collected. A total of six phytoplankton species were recorded, developing with the following blooming concentrations: Emiliania huxleyi, Oscillatoria sp., Merismopedia sp., small Flagellates (Cryptophyceae), Prorocentrum cordatum (minimum) and Pseudo-nitzschia delicatissima. It was found that the reported in previous periods trend of increasing phytoplankton biomass in front of cape Galata had already changed. Compared to the observed quantities in the period 1993-2007, the current phytoplankton values in the surface layer (up to 30 nm in front of cape Galata) were 1.63 times lower in abundance and 5.60 times lower in biomass.