Evolution of water quality level related to phytoplankton composition in Sultansuyu and Sürgü Dam Lakes

Besides being fishing and recreational sites, Sultansuyu and Sürgü Dam Lakes, located in Malatya province, are built for irrigation purposes.Depending on water quality, two sampling points were selected to determine phytoplankton composition in these Lakes. Vertical water and phytoplankton samples were collected from the selected locations between July 2008- 2009 at the same time points of the season and their physico-chemical parameters were analyzed. The samples collected from surface and Secchi disk depth were utilized for the quantification of chlorophyll-a, chlorophyll-b, carotene, and pheopigment were measured which were.A total of 114 taxa were identified in Sultansuyu Dam Lake. Of these taxa 14 belong to Cyanobacteria, 55 Chlorophyta, 28 Bacillariophyta, 11 Myzozoa, 4 Euglenozoa, 1 Chrysophyta, 1 Rhodophyta. Off 96 taxa identified in Sürgü Dam Lake, 12 belong to Cyanobacteria, 44 Chlorophyta, 31 Bacillariophyta, 7 Myzozoa, 1 Euglenozoa, 1 Chrysophyta.Distribution of the identified species on the sampling locations were analyzed according to frequency, density, dominance, diversity and similarity. These results were tested by Unweighted Pair- Group Method Using Arithmetic Averages (UPGMA).In addition, by the Canonical Correspoinding Analysis (CCA) used, multiple relations between environmental variables that effect structure of dam lakes and phytoplankton density have been analysed. Depending on the sampling points, the effect and degree of environmental factors on phytoplankton composition have been shown on triplot graphs. The distribution and similarities of sampling points under environmental variables were also analysed by UPGMA and shown in Cluster dendograms.According to water quality values, the trophic level of Sultansuyu Dam Lake was determined as ultraoligotrophic and oligomesotrophic, while the level of phytoplankton species were determined as oligosaprobic, ß-mezosaprobic. The trophic level of Sürgü Dam Lake was determined as ultraoligotrophic and mesotrophic, while the level of phytoplankton species were identified as oligo-ß-mezosaprobic and ß-mezosaprobic. As a result, both lakes are found to have oligotrophic tendency with mesotrophic trophic level.KEY WORDS: phytoplankton, chlorophyll-a, chlorophyll-b, carotene, phaeopigment, water quality, Sultansuyu Dam-Lake, Sürgü Dam-Lake