How do environmental variables affect the temporal dynamics of zooplankton functional groups in a hyper-eutrophic wetland?

Abstract

In recent years, trait-based research on zooplankton has gained importance to enable comprehensive interpretation of ecosystem processes, but this approach is still limited in inland waters. Wetlands, one of the most important inland water resources, provide many ecological and economic services in the ecosystem, but like all other water bodies in the world, they are under threat of deterioration and depletion for various reasons. In this study, the taxonomic structure of the zooplankton community in Lake Manyas, one of the important wetlands of Türkiye, as well as their functional characteristics such as body size (small, large) and feeding strategies (microphagous, raptorials) were investigated monthly between 2019 and 2020. The hypothesis that environmental variables influence the species composition and functional groups of zooplankton was tested, given that their structure is shaped by environmental gradients. A total of 62 taxa, including rotifer-dominated, cosmopolite and eutrophication indicator species, were identified. These taxa categorized into three functional groups dominated by small microphagous. Although the zooplankton structure had a high taxonomic diversity, functional homogeneity was observed which reflected a low grazing rate in the ecosystem. Albeit water temperature and total organic carbon significantly affected the distribution of all functional groups, each dominant taxa interacted with different environmental variables. Changing environmental conditions in the lake affected the presence and/or quantity of the zooplankton functional groups (ZFGs). The results showed that ZFGs are strongly associated with environmental conditions and that the response of trait-based functional groups to environmental changes can provide useful knowledge about aquatic ecosystem’s health.