Mäkkýše hlavných typov vôd dolného Hrona [Mollusca in main water bodies in the lower Hron River, Slovakia]

The aim of this study is to describe the main types of water bodies in the lower Hron River (Slovakia) using Mollusca as ‘functional describers’ of the ecosystem dynamics. In European context, the Hron River belongs with its average discharge 53.7 m³.s^–1 to small rivers; course length is 297 km. Major part of the alluvial plain exhibits strong human impact, though there are still relics of relatively well-preserved main successional stages of water bodies. The sampling (set-time period method) was stratified on the distribution of aquatic macrophytes (if presented). A total of 35 species was found alive (23 gastropods, 12 bivalves). The most constant species were Radix auricularia and Galba truncatula. In eupotamon, 13 species were found; characteristic species were Valvata piscinalis, Gyraulus albus, Unio pictorum, U. tumidus, Pisidium spp., Ancylus fluviatilis, and Radix peregra. In parapotamon, the bivalve Sphaerium corneum was a characteristic species, plesiopotamon had no characteristic species; for paleopotamon were characteristic Planorbis planorbis and Aplexa hypnorum, also a non-indigenous snail Physella acuta was constant. In anthropogenic water bodies no differentiative species were presented; the presence and dominance of Physella acuta is typical.