SEASONAL DYNAMICS OF CLADOCERA SPECIES IN ZOOPLANKTON COMMUNITIES OF THE FERGANA VALLEY, UZBEKISTAN

Abstract

Cladocerans are among the most important components of freshwater zooplankton communities, playing a key role in energy transfer, algal grazing, nutrient cycling and the assessment of ecological conditions in inland water bodies. However, seasonal changes in Cladocera communities in the water bodies of the Fergana Valley remain insufficiently documented, despite the region's high hydroecological diversity and increasing anthropogenic pressure. This study aimed to analyze the seasonal dynamics of Cladocera species composition, abundance, biomass and ecological structure in selected water bodies of the Fergana Valley, Uzbekistan. Zooplankton samples were collected from [number] sampling stations located in lakes, reservoirs, canals, fish ponds and temporary water bodies during [spring, summer, autumn, winter / exact months] of [year]. Samples were obtained using a plankton net with a mesh size of [50-64 micrometers], preserved in [4% formaldehyde / 70-96% ethanol], and examined under a light microscope. Species identification was performed using standard taxonomic keys, while abundance, biomass and diversity indices were calculated for each season. A total of [number] Cladocera species belonging to [number] families and [number] genera were recorded. The highest species richness was observed in [season], whereas the lowest values were recorded in [season]. Seasonal changes were mainly associated with water temperature, hydrological stability, trophic conditions, macrophyte development and the availability of suitable littoral habitats. The families Chydoridae and Daphniidae showed different seasonal patterns: littoral and phytophilous chydorids were more diverse in vegetation-rich habitats, while planktonic daphniids and moinids showed higher abundance during warmer periods. The results indicate that Cladocera communities in the Fergana Valley are highly sensitive to seasonal environmental fluctuations and may serve as useful indicators of ecological changes in freshwater ecosystems.