Major shifts in the phytoplankton community of the Romanian Black Sea waters Laura Boicenco National Institute for Marine Research and Development “GRIGORE ANTIPA”, Constanta, Romania

Phytoplankton sampled station in Romanian waters

Eutrophication process at the Black Sea coast in the ’70ies and ’80ies had important modification of the marine ecosystem: biodiversity loss reduction of living marine resources expansion of frequency, magnitude and spatial extension of algal blooms mass mortality of marine animals caused by hypoxia and anoxia

Abundance of the species involved in the main blooms in 1960 – 2003 period

Annual phytoplankton quantitative mean for 2000-2003 and multi-annual mean for nineties and following decades in Constanta near-shore waters

Mean values of most important nutrients between 2000 and 2002 and some previous periods in Constanta near-shore waters

Proportions of the main algal groups in the numerical density means of the phytoplankton in Constanta near-shore waters

Number of phytoplankton species with massive development in the Romanian coastal waters during 1983 – 2003 period

Multi-annual mean of the phytoplankton quantities in the near-shore Constanta marine waters during 1986-2003 period

Mass mortality of marine animals caused by hypoxia, in July 2001

Conclusions: nutrient concentration in the ’90ies still relatively high, compared with period 1960-1970 the bloom frequency and magnitude in the ’90ies decreased after decline of nutrient supply diatoms became dominant in the phytoplantkon structure diatoms share and tendency of shifting of annual maximum algal development from summer to spring and autumn, seem to be signs for evolution towards normal status of plankton algal community