Species Composition, Ecological Parameters and Seasonal Changes of Planktonic Ciliates Population in Bukan Dam Reservoir

Problem Statement: Since there is no evidence to identify present species in the Bukan dam reservoir, therefore, this study was conducted to provide background for fisheries purposes. Approach: The abundance and species composition of ciliates were analyzed in the Bukan Dam reservoir (west Azerbaijan, Iran) from January to December 2007. Surface water samples were collected at monthly intervals at two different points, open water (Station 1, 3) and in the shallowest area of the reservoir (Station 2, 4) and examined for planktonic protozoa composition and density. Chlorophyll a was analyzed and a few ecological parameters such as dissolved oxygen, pH, turbidity and temperature were measured. Results: Totally 50 ciliates species were found in Bukan dam reservoir. Concerning the protozoa density, a high-density period was detected from January to April with a mean number of 2.86×103 cells.L^-1 protozoa at Stations 1, 3 and 4.16×103 cells.L^-1 protozoa at shallowest areas at stations 2, 4 thanks to disappear of phytoplankton in the winter. The summer development of protozoa was possible thanks to the development of bacteria and moderate metazooplankton densities due to the appearance of non-edible algae. The density of ciliates was low during the rest of the year. The mean number of organisms at the high-density period was approximately 4-fold more than that obtained during the low-density one. The ciliates occurring at the highest densities were Coleps tessellates, Paradileptus elephantinus, Zosterograptus labiatus, Cyclidium citrullus. Conclusion/Recommendations: It was concluded that ciliates density have important role for saprobic condition of Bukan reservoir. Therefore, it can be recommended to determine more effective parameters for density of ciliates and management policies must be programmed in order to improve ecological condition for this reservoir.