Directional changes in environmental conditions during individual stages of the succession of lakes should determine the character of the aquatic beetle fauna inhabiting them. Can changes in environmental conditions lead to degradation of fauna and to a deterioration of the ecological quality of lakes? We analysed this problem in 40 lakes. The fauna of the lakes proved to be rich and diverse in terms of species. Deterioration of species richness along successional stages was not observed, but distinct changes were noted in faunal composition. The eurytopic component proved stable, whereas changes in specialised components (i.e. lake and river species and tyrphophiles) were of key importance. The formation of beetle communities in the lakes was influenced to a greater extent by environmental factors, namely substrate, macrophyte structure and Sphagnum mat cover, than by the physical parameters of the water (pH, saturation or conductivity). The lakes proved to be of considerable ecological value. Regardless of the stage of succession, they are a habitat for numerous species, including rare and endangered ones. Hence, on the one hand humic lakes play an important role in local biodiversity, whereas on the other hand they may be perceived as refuges for species in environments that could be restored as a result of beneficial measures.
The impact of dredging of a small lowland river on water beetle fauna (Coleoptera)