Distribution and ecology of Cladocera in Lake Khojahasan, Absheron Peninsula, Azerbaijan

Abstract

The distribution and ecology of Cladocera were studied in Lake Khojahasan, located on the Absheron Peninsula of Azerbaijan, in 2023– 2025. Samples were collected from several stationary points of the lake using plankton nets and net skimmers on a seasonal basis; qualitative samples were analysed in 70% alcohol and quantitative samples were counted in a Bogorov chamber. As a result of the studies, seven species of Cladocera were identified in Lake Khojahasan: Daphnia magna , Daphnia longispina , Daphnia pulex , Alona rectangula , Chydorus sphaericus , Ceriodaphnia reticulata and Moina rectirostris . The distribution of the species differed by water depth, coastal region and season. According to the data obtained, the average annual abundance of Cladocera varied between 930 and 1743 individuals/m 3 during 2023–2025, with the peak period of development observed in June. Dominant species varied by year and season, with Moina rectirostris and Ceriodaphnia reticulata noted as the main dominant species. Abiotic parameters (water temperature, pH, salinity and transparency) were also measured and their influence assessed. As a brackish-water lake, Lake Khojahasan forms a favourable environment for the species composition and abundance of Cladocera, both because of its morphological characteristics and despite the anthropogenic impact it receives.