Chironomid (Diptera: Chironomidae) larvae play an important role in a wide range of aquatic ecosystems. The study focuses on Chironomidae trophic guilds and morphological types as indicator traits in reconstructions of habitat changes in shallow water bodies. Mentum and ventromental plates are important mouthparts whose shape depends on food type and feeding behavior. Chironomidae larvae strongly vary in the mode of life and feeding habits, representing almost every feeding group. Here we classified the mentum types into 16 groups and tested if they indicated similar past habitat changes as the Chironomidae functional feeding groups (FFGs), and tribes/subfamilies. Paleoecological data of biotic and abiotic proxies were derived from short sequences from a Late Glacial oxbow and a nearby medieval moat located in Central Poland. The study revealed that the habitat substratum structure, vegetation and physicochemical conditions are associated both with the feeding types and morphological traits. This provides a valuable tool for future reconstructions of habitat changes.

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Chironomidae and Cladocera are useful palaeoindicators to describe long-term dynamics in biodiversity of freshwater aquatic communities. However, palaeoecological studies relying on these aquatic invertebrates have generally focused on post-glacial lakes, with relatively few applications to floodplain water bodies such as palaeo-oxbow lakes. In this study, zone-level (stratigraphic) trends in Chironomidae and Cladocera assemblage composition were analysed from a small palaeo-oxbow lake in a Central European river valley of Poland. Summer air temperature and hydrological conditions were found to be the main drivers of Cladocera and Chironomidae populations, causing a cascade effect in assemblage composition. At the local habitat scale, there were autecological differences in both taxonomic groups reflecting different responses to abiotic and biotic factors. Specifically, Cladocera responded distinctly to plant vegetation and fish predation during the Late Glacial lake phase, whereas Chironomidae were more sensitive to paludification processes and disappeared in the Northgrippian dry phase of the mire. Both groups indicated fluvial activity of the River Grabia, although the response was different. Also, species richness was higher in the more taxonomically diverse Chironomidae compared to Cladocera. As both groups responded to the same factors in a different way, it is recommended that they should be used in parallel in palaeoecological research studies.