Analysis of Macrobenthic Communities in a Post-Mining Sulphur Pit Lake (Poland)

The objective of the study was to define the primary environmental factors affecting the composition of the macrobenthic community in an abandoned open cast sulphur mine pit lake that had been filled with water from a nearby river. We investigated habitats at various depths and the macrobenthic communities; samples were collected by scuba divers. Although rush and submerged vegetation in the subsaline pit lake was abundant and provided potentially good habitat conditions for mayflies, caddisflies, coleopterans, or damselflies, the native insects were scarce. The taxa do not have many representatives in waters with elevated salinity, so those present in the Machów pit lake were mainly euryhaline species. Chironomids were the most abundant macroinvertebrates in shallower zones, whereas non-native zebra mussels were the quantitatively dominant taxon in deep-water zones. Moreover, these non-native mussels were the dominant biomass of invertebrates at all sites in all seasons. The current composition of the invertebrate assemblage was probably primarily determined by the salinated water, which limited the abundance of native species and gave non-native species an edge.