An investigation on the phytoplankton and its seasonal variation of Lake Sera (Trabzon)

The aim of this study is to determine the composition, abundance, seasonal variations and both physical and chemical factors effecting these variations of algae in Lake Sera at four selected sampling sites between December 2010 and November 2011. During the research, total 61 taxa has been identified, 45 of which belong to Ochrophyta, 6 to Euglenozoa, 5 to Dinophytha, 4 to Chlorophyta and 1 to Cyanobacteria. Considering the number of taxon, frequency and abundancy at the stations, members of Ochrophyta have been the most dominant algae division. The members of this division were dominant especially in winter and they reached the maximal level in February and August. Euglenozoa was to be found the sub-dominant group and these two groups were subsequently followed by Chlorophyta, Dinopthyta and Cyanobacteria. The percentages of algal groups in terms of abundancy were as follows: Ochrophyta 74 %, Euglenozoa 10 %, Chlorophyta 8%, Dinophyta 5 % and Cyanobacteria 2 %. Although physical factors such as light and temperature have limiting effect, chemical properties such as pH level have not limiting effect on the growth of phytoplankton. The increase in the variations of the species was found to be paralel with the increase of the temperature. The values belonging to chemical parameters were found to be in between normal limits. The results suggest that in our research area there is a dominancy of the diatom population which prefers slightly alkaline water and it is relatively poor in terms of its organical algal abundancy. Key Words: Lake Sera, Phytoplankton, Seasonal Variations, Diatoms