Biological recovery of acidified alpine lakes may be delayed by the dispersal limitation of aquatic insect adults

Abstract

The dispersal of aquatic insects plays an important role in the colonization and recolonization of newly created and previously disturbed habitats. The heavy acidification of some alpine lakes in the Tatra Mountains, Slovakia, was followed by rapid chemical recovery starting in the 1990s; however, the recolonization of aquatic insects has been delayed, potentially due to the limited dispersal of aquatic insects in the alpine environment. Therefore, to investigate dispersal ability of aquatic species in situ, we set up 120 yellow pan traps on 12 transects evenly distributed over a distance of about 600 m between a non-acidified and a formerly acidified alpine lake. A total of 1,202 aquatic insect adults were caught. Chironomidae dominated but adults of Trichoptera, Plecoptera and Ephemeroptera were also recorded. For both lakes the total number of adults declined exponentially with distance from the lakes, and negative binomial models predicted that virtually no imagoes would be found beyond 300 m from the lakes. The majority of species were recorded within 150 m of the lake shore with the exception of two chironomid species. Such a low dispersal potential of aquatic insects between alpine lakes could explain the slow biological recovery of some lakes following disturbance by acidification stress.