Cladocera assemblages indicate environmental gradients of lake productivity and morphometry in central Europe

Abstract

Lakes play a vital role in numerous human activities, yet extensive economic development has led to significant pollution and nutrient enrichment, resulting in widespread eutrophication and ecological disruption. To accurately assess the current state of lakes, it is essential to understand their historical, pre-impact conditions. Palaeolimnological methods, including the analysis of subfossil Cladocera, offer a valuable tool for studying lake ecosystems over extended timeframes that go beyond modern instrumental records. Our research aims to identify the primary environmental factors that influence the distribution of individual Cladocera species and evaluate the systematic patterns within species assemblages to enhance their use as ecological indicators. This study presents an analysis of Cladocera assemblages based on environmental surveys conducted in 64 lakes across northeastern Poland. Principal component analysis revealed that the two dominant factors driving variability in the dataset are lake trophic state, indicated by total phosphorus (TP) levels, and lake depth. Species distributions across these gradients showed a turnover, reflecting distinct environmental preferences. Further, end member (EM) analysis identified five distinct assemblages of Cladocera, each associated with specific combinations of trophic status and lake size. EM1 is associated with higher trophic states, while EM2, EM3 and EM4 are indicative of medium to low trophic states. EM5 is independent of trophic status, associated with large and deep-water bodies.