Seasonal changes on phytoplankton dynamics in eastern black sea ecosystem

Temperature, dissolved oxygen, salinity, conductivity, nutrients ( N02-N, NO3-N, P04-P, Si02), iron, chlorophyll-a and, quantitative and qualitative distribution of phytoplanktonic organisms were investigated in the Eastern Black Sea Marine Ecosystem, Trabzon, from January 1993 through to August 1994. Species belonging to Bacillariophyceae and Dinophyceae were observed to be dominant in planktonic community. The highest number of cells were found in May. During the bloom period, Chlorella sp. and Emilicmia huxleyi were observed in the sub-surface water, whilst Nitzschia closterium, Rhizosolenia fragilissima, Rhizosolenia calcar-avis and Peridinium trochoideum were found in surface water. The highest value of chlorophyll-a was measured as 3.7 ug/1. However, mean values of chlorophyll-a were obtained as 0.60±0.48, 0.57 ± 0.63, 0.20 ± 0.094 ug/1 for surface, 10 m and 25 m in depth, respectively. During the study, N02-N, N03-N, P04-P, Si02 and iron values were measured between 0.001-0.007 mg/1, 0.1-1.4 mg/1, 0.01-0.77 mg/1 and 0.110-3.760 mg/1 and 0.001-0.070 mg/1 respectively. It was observed that mere was an interaction between iron and chlorophyll-a at the depth of 10 m. Keywords : Black Sea, Phytoplankton, Chlorophyll-a, Nutrients. VI