Temporary changes of the trophic status in Lake Mogan

In this study, it is aimed to examine the temporal changes of the trophic state of Mogan Lake, which is of recreational importance due to its proximity to Ankara. Water samples were taken from two different points seasonally between May 2022 and February 2023. Depth, Secchi depth, water temperature, pH, total dissolved solids, alkalinity, electrical conductivity, dissolved oxygen, oxygen saturation, chlorophyll a, and total phosphorus values were determined in the sampling points. The Carlson Trophic State Index was calculated using the chlorophyll a, total phosphorus, and Secchi depth values, and the trophic status of the lake was estimated. Furthermore, the Carlson Trophic State Index was also calculated using data obtained from previous studies conducted in the lake, and a 34-year change was analyzed based on TSI, OECD, and YSKY. In Lake Mogan, the TSI (AVG) value was calculated as 52,46 and the trophic status of the lake was determined as eutrophic. Differences in TSI (AVG) values among all months and sampling points were found statistically significant (p<0,05). Based on the TSI values calculated using data from previous years, it was determined that the trophic structure of the lake still maintained a eutrophic level over a 34-year period. A similarity test (Bray-Curtis Similarity Index) applied to the TSI (AVG) values obtained for different years showed a strong similarity between the values in 2023 and those in 1989. As a result, preparing precautionary plans against eutrophication of Lake Mogan and monitoring the trophic status via TSI is recommended.