Küçükçekmece Lagoon, located inside the Istanbul metropolitan area is B-class wetland that is considered one of the most important waterbody in the region. It is connected to the Marmara Sea by a small canal. Due to rapid industrialization and population growth, a significant deterioration in water quality has been observed since the 1990s. Due to the construction of a dam on Sazlıdere stream, which is the most important feeding source for the lagoon, there has been a decrease in freshwater inflow, so the amount of salinity in the lagoon has started to increase. While salinity was around 11 ppt at the surface water of the lagoon in the 2010s, the level of salinity concentration exceeds 17 ppt today which also has an impact on the ecosystem.
The aim of this study is to evaluate the water quality changes in the Kucukcekmece lagoon in a decade. For this purpose, the temporal and spatial distribution of silicate, nitrate, nitrite, phosphate, chlorophyll-a, temperature, salinity, and dissolved oxygen in Küçükçekmece Lagoon were analyzed in three stations. Moreover, water samples were collected from the water column in the middle of the lake to detect anoxic conditions measuring H2S concentrations. According to Carlson Trophic Index, Küçükçekmece Lagoon has a hypereutrophic character for a decade. The water quality revealed a high spatial and temporal variation in the lagoon and the bottom (ca 18 m) waters were rich in H2S of which the highest concentration was measured as 215 mg/L. Overall, from the large dataset of water quality for more than ten years, there is an obvious effect of anthropogenic activities and the closure of freshwater inlets on the trophic conditions of the lagoon.
