Phytoplankton of Doğancı dam lake (Bursa) and determination of trophic level

In this study, some physico-chemical and heavy metal analyses and phytoplankton identification and counting were carried out in the samples taken from Doğancı Dam Lake between January 2018 and November 2018. The trophic level of Doğancı Dam Lake has been determined. The water quality of Doğancı Dam Lake was also evaluated according to the Regulation on the Quality and Treatment of Drinking Water Supply criteria. The water quality of the dam is 1st class water quality. In Doğancı Dam Lake phytoplankton, 14 taxa from Cyanobacteria (17,72%), 4 taxa from Miozoa (5,06%), 1 taxon from Ochrophyta (1,27%), 12 taxa from Chlorophyta (15,19%), 4 taxa (5,06%) from Charophyta, 44 taxa (55,70%) from Bacillariophyta, a total of 79 taxa were identified. In Doğancı Dam Lake, the species that spread every season during the whole study period are Asterionella formosa, Stephanocyclus meneghinianus, Fragilaria crotonensis, Mougeotia sp., Nitzschia acicularis, Planktothrix rubescens, Ulnaria delicatissima and Ulnaria danica. In Doğancı Dam Lake, the highest total organism density was seen in October with 1 825 685 org/L, and the lowest total organism density was observed in January with 54 org/L. As a result of the cyanotoxin analysis, no toxins were detected in the dam water. However, it was concluded that the reservoir should be monitored continuously due to the potential of Dolichospermum planctonicum and Planktothrix rubescens to produce toxins. The trophic level of Doğancı Dam Lake was calculated according to Carlson's (1977) Trophic Level Index (TSI) values. According to TSI(CHL) values, Doğancı Dam Lake was observed to have a mesotrophic character, but for the TSI(TN) values, it was an oligotrophic character. According to the results of the explanatory factor analysis (EFA) applied to reveal which environmental variables are important in Doğancı dam lake water, three factor loads were determined in the dataset, which explain 80,752% of the total variance. It has been determined that the first factor load is related to the geological structure of the basin and climatic factors. In the second and third factor loads, it is seen that besides the geological structure, nutrient salt, suspended solids, and phytoplankton are important. According to the results of the redundancy analysis applied to determine the relationship between species and environmental variables, volume (p= 0.002; F= 5.77), pH (p= 0.002; F= 5.73), water entering (p= 0.002; F= 5, 29), evaporation (p= 0.002; F= 2.65), water temperature (p= 0.004; F= 2.40), nitrate (p= 0.040; F= 1.58) and magnesium (p= 0.048) ; F= 1.65) was found to be significant.