Distribution of Benthic Fauna in Relation to Environmental Conditions in an Inundated Opencast Sulphur Mine (Piaseczno Reservoir, Southern Poland)

Highly specific environmental factors such as the presence of strongly mineralized water, oxygenation of the water down to 10 m, a low trophic status of the water and low organic matter content in the bottom sediments, were found in the studied post-exploitation Lake Piaseczno. Of the 42 macroinvertebrate taxa found, Oligochaeta (Tubificidae) and Chironomidae predominated. Almost exclusively ubiquitous species were found, except for some chironomid taxa recorded for the first time in Poland. The most diversified faunal communities occurred at 1 m water depth whereas the highest densities were found at 5 m. At the deepest points studied only oligochaetes and Chaoborus flavicans were found. There was no correlation between organic matter content and macrofauna densities. Differences in inhabitation at the studied transects could result from various environmental factors such as the degree of macrophyte cover and protection from the wind. Undisturbed transects overgrown by macrophytes had a similar community composition and higher faunal densities than those which were less protected.