Changes in chromophoric dissolved organic matter in seyhan and çatalan dam lakes depending on some environmental factors, time and space

Natural lakes and artificial ponds/reservoirs constitute usable inland water reserves. The gradual deterioration of these resources due to factors such as global climate change, land use changes, industry, and industrial agriculture has made it imperative to identify, protect, and manage their quality. Chromophoric dissolved organic matter (CDOM), the optically active portion of dissolved organic matter (DOM), a complex mixture of molecular particles containing carbon, nitrogen, phosphorus, and sulfur with varying molecular weights in aquatic ecosystems, arises from autochthonous and allochthonous sources. Identifying the sources of CDOM by measuring the parameter is important for understanding biogeochemical carbon cycles, ecosystem integrity, and water quality management. The Seyhan and Çatalan Dam reservoirs constructed on the Seyhan River are two important sequential water reservoirs for the Çukurova Region. Monthly sampling and on-site measurements were conducted at three selected stations in each reservoir between July 2024 and August 2025. Depth, Secchi depth, and temperature measurements were taken at the stations, and water samples were collected for aCDOM(350) analysis using a Niskin-type water sampler from three different depths representing the middle and bottom regions, including a composite in the euphotic zone. UV-Vis spectrophotometer measurements revealed an average aCDOM(350) of 2,884±2,120 m-1 for Çatalan Dam Lake and 2,567±1,639 m-1 for Seyhan Dam Lake throughout the study. According to the variance analysis, while monthly changes had a significant effect on CDOM (p<0,001), station, lake, and station×lake interactions were not statistically significant (p>0,05). These findings suggest that CDOM is spatially homogeneous but temporally variable. The source of CDOM in both lakes is autochthonous material.