Environmental factors affecting the spatio-temporal distribution of zooplankton functional groups in a deep alkaline lake

In recent years, trait-based studies have gained importance as an extension of taxonomic studies to better understanding ecosystem processes. However, these studies are still very limited in Mediterranean freshwaters. The aim of the study was to link functional groups with environmental factors and ecosystem processes for zooplankton in the Lake Iznik, which is an alkaline lake in Türkiye. Morphological, physiological and behavioural categories have been selected as response traits. Physical and chemical variables and trophic state are important predictors of functional traits. A total of 26 zooplankton taxa belonging to four taxonomic groups were classified into five functional groups according to functional traits. It was found that functional groups were significantly affected by seasonally changing environmental conditions, but not by depth. The main predictor of zooplankton functional groups was electrical conductivity. As a result of the alkaline conditions and the deterioration of the trophic state of the lake (meso ~ to eutrophy), the low taxonomic richness, dominance of the microphagous feeding type and small-bodied taxa indicate ecosystem degradation leading to functional depletion (homogenisation). The results showed that temporal variations of environmental variables can affect zooplankton functional groups and that trait-based zooplankton studies will enable a better understanding of ecosystem processes in deep alkaline lakes.