Algal Blooms in Surface Waters of the Sinop Bay in the Black Sea, Turkey

Abstract

During the investigation period of August-1995 and July-1996, 22 algal species reached numerical densities exceeding 1.0x10 cells LG and it has been produced 17 mono-specific blooms by 11 of them reached 5 1 values of the order of 1.0×10 cells LG (one of them exceeding 1.0×10 cells LG ) in surface waters of the Sinop 6 1 7 1 Bay. A monthly average of cell number has been estimated as 7.1×10 cells LG in the surface waters. In the 6 1 diatom communities, subsequent blooms were dominated by Nitzschia longissima (5.2×10 cells LG ) 6 1 and Cheatoceros danicum (2.7×10 cells LG ) in January, Ditylum brightwelli (7.6 × 10 cells LG ) in March, 6 1 5 1 Pseudo-nitzschia delicatissima (9.0×10 cells LG ) in April, Cylindrotheca closterium (7.4×10 cells LG ) in early 7 1 6 1 July, Rhizosolenia calcar-avis (1.7×10 cells LG ) and Pseudo-nitzschia pungens (1.2×10 cells LG ) in late 6 1 6 1 July and mid-August. Subsequent blooms in the dinoflagellate communities were dominated by Heterocapsa triquedra (1.0×10 cells LG ) and Protoperidinium depressum (1.0×10 cells LG ) in March , 6 1 5 1 Protoperidinium granii (4.8×10 cells LG ) and Scripsiella trochoidea (7.8×10 cells LG ) in June, 5 1 5 1 Prorocentrum balticum (9.0×10 cells LG ) and Prorocentrum compressum (4.6×10 cells LG ) in mid-July, 6 1 5 1 Gonyaulax polyedra (1.4×10 cells LG ) in June, Prorocentrum micans (7.2×10 cells LG ), 5 1 5 1 Prorocentrum minimum, Protoceratium aerolatum, Protoperidinium longipes (2.0×10 cells LG ) in 5 1 mid-August and Prorocentrum aporum (1.0×10 cells LG ) in December. The highest cell numbers of 6 1 prymnesiophyte Emiliania huxleyi (5.9×10 cells LG ) was observed in mid-July. Results showed that the 6 1 declines of diatoms were followed by increases of dinoflagellates. Dinoflagellates began to increase in late-March, reached a maximum in Mid-July and gradually declined towards October. In contrast to the diatom, dinoflagellates dominated mid-spring, late summer and mid-winter populations, dinoflagellate blooms showed more pronounced in late spring and mid-summer. The mean of cell numbers of total phytoplankton in surface waters was high in April (3.4×10 cells LG ) and July (1.3×10 cells LG ), while was low in February 7 1 7 1 (9.0×10 cells LG ), respectively. A list of excessive and potential excessive phytoplankton species together with 5 1 numerical densities were prepared. Changes in number and density of algal blooms during the year were also discussed in relation to the physico-chemical features of the water column.