Early post-dredging recolonization of caddisflies (Insecta: Trichoptera) in a small lowland river (NW Poland)

摘要

An analysis was made of the effect of dredging on the caddisfly fauna (Trichoptera) of the river KrA...piel (north-western Poland) a short time after the intervention. Pronounced changes were observed in the qualitative and quantitative structure and the biodiversity of Trichoptera. These changes should not, however, be characterized as unfavourable from an ecological perspective if we consider only the one group of insects analysed. Some species - Brachycentrus subnubilus and Lepidostoma hirtum - disappeared from the dredged parts of the river, but significantly more appeared, and these were typical river species. This replacement of species can be linked to habitat changes and the uncovering of larger patches of sandy bottom. The recolonizing species included accidental (eurytopic) species, which is typical in ecological succession for periods immediately following disturbances. On balance, despite the replacement of species, there was no decrease in species diversity, and typical river species appeared in larger numbers. In Trichoptera, recolonization following dredging first takes place as a result of drift of larvae, and then via dispersion of adults.