Trophic Status of a Shallow Lake (North of Iran) Based on the Water Quality and the Phytoplankton Community

This study was carried out on Carlson Trophic State Index (TSI) for assessing trophic status in a shallow wetland (Marzanabad) that located in southwest (SW) of Babol city in north of Iran. The qualitative and quantitative characteristics of phytoplankton community and also environmental variables were determined and compared with the TSI in order to describe the water quality status. In three stations, the water samples were collected in Sept. 2006 through Aug. 2007; except January. In this research, 97 taxa from 6 algal classes such as Bacillariphyta, Chlorophyta, Chrysophyta, Cyanophyta, Dinophyta and Euglenophyta were identified. This wetland water was opened indirectly to Haraz River for 6 months, so phytoplankton composition was different during the year. During the isolation from Haraz overlapping with warm months, the phytoplankton community was dominated by species as Nitzschia spp, Binuclearia tatrana, Euglena spp and specially Oscillatoria spp, respectively. But in late Autumn to early spring species as Dinobryon divergense and Gymnodinium paradoxum were dominated and coinciding with the minimum Shannon-Weaver diversity index that recorded in winter. The Palmer organic pollution index revealed high organic pollution in whole of the year. TSI data and some other criteria indicated that the area has high trophic level.