Temporal variations of phytoplankton in relation to eutrophication in Samsun Bay, southern Black Sea.

Abstract

The goal of this study was to determine the monthly variations of phytoplankton composition in the least studied southern shores of the Black Sea with respect to environmental factors. This region is known to be one of the most eutrophic seas in the world. During the course of this research, carried out between October 2002 and September 2003, various samples were collected monthly from a depth of 0.50 m at five stations. A total of 129 taxa belonging to 5 divisions and 14 potentially HAB species was recorded during this research. Three peaks were observed in the total phytoplankton in October 2002, May and July 2003. These findings were also supported by chlorophyll a (chl a) concentrations and the biodiversity index of Shannon-Wiener (H’). TRIX indices were computed in order to identify the trophic level of the region and the research area was determined to be highly eutrophic. Three groups of samples were described by Hierarchical agglomerative clustering and Multi-Dimensional Scaling (MDS) ordination. Species displaying a major role in discriminating the groups were Dactyliosolen fragilissimus (Bergon) G.R. Hassle, 1997, Nitzschia longissima (Brebisson) Ralfs in Pritchard, 1861, Proboscia alata (Brightwell) Sundstrom, 1986, Pseudonitzchia pungens (Grunow ex P.T. Cleve, 1897) Hasle, 1993 and Skeletonema costatum (Greville) P.T. Cleve, 1878 from diatoms, Prorocentrum micans Ehrenberg, 1833 from dinoflagellates and Eutreptia lanowii Steur 1904 from Euglenophyta.