A research on the trophic structure of Lake Gölünyazı (Çorum)

In this study, monthly samples were taken from 6 stations determined on the stream between April 2021 and March 2022 to determine the phytoplankton and benthic diatoms of Gölünyazı Lake (Çorum). The samples were counted and identified, and the seasonal changes of the algae were determined. In the study, a total of 45 taxa belonging to the divisions Bacillariophyta (30), Chlorophyta (4), Euglenozoa (4), Cyanobacteria (2), Charophyta (2), Cryptophyta (1), Miozoa (1) and Ochrophyta (1) were identified in the phytoplankton flora. The algae group with the highest number of organisms in Gölünyazı Lake phytoplankton is Bacillariophyta, followed by Euglenozoa. In benthic algae (epiphytic and epilithic), total 41 taxa belonging to 13 orders of the Bacillariophyta division were identified. Within the Bacillariophyta division, the dominant algae order was the Naviculales team, which includes 10 taxa. In addition, physicochemical analyzes of the water samples taken from the stations were made, and the relationship between the obtained data and the detected organisms was tried to be determined. Diversity, regularity, frequency, and NMDS analyzes of phytoplankton and benthic diatoms were made, and their water quality indicator status was determined. In addition, the Phytoplankton Community Index (Q index) of the phytoplankton species and the Trophic Diatome Index for Lakes (TDIL) of the benthic diatoms were calculated, and the water quality was tried to be determined by using the indicator characteristics of the species identified in the study area. According to the phytoplankton community index (Q index) results, it was determined that the ecological water quality of Gölünyazı Lake was classified as "very good". However, the fact that the dominant and subdominant organisms of our study area are mostly tolerant species shows that there is pollution pressure in the aquatic area. According to Shannon diversity index, it has been seen that the lake is in the "Poor" ecological quality status and "Oxygen-Free-Highly Polluted" pollution class. Whereas, pollution-tolerant species were more common in phytoplankton, while pollution-sensitive species were more common in phtobenthos (epiphytic and epilithic flora). According to the results of the Trophic Diatom Index for Lake (TDIL) calculated on the epiphytic and epilitic algae, Gölünyazı Lake has been determined to have a eutrophic ecological status corresponding to the "bad" water quality class. When the data in the study area were evaluated, it was seen that Gölünyazı Lake is facing the threat of pollution. In order to protect the aquatic ecosystem of Gölünyazı Lake, either the lake surroundings should be transformed into pasture areas or organic farming should be encouraged around the lake. Thus, the polluting factors of the lake should be kept under control. In addition, in order to protect the biodiversity and wetland in Gölünyazı Lake, it is important to ensure a controlled water inflow to the lake area from the surrounding streams during dry seasons. Key Terms: Lake, water quality, phytoplankton, phytobenthos, indices. Science Code: 20322