Interaction of the Danube river and its left side tributaries in Slovak stretch from benthic fauna point of view

In the Danube river and its Siovak tributaries, 207 zoobenthos taxa belonging to 20 systematic groups have recently been found. 144 taxa of 18 groups were recorded in the Danube river. Many representatives of Danubian and Ponto-caspian molluscs and crustaceans as well as the caddis fly Hydropsyche bulgaromanorum were collected in the Danube main stream and its tributaries. The presence of rare and threatened mayflies such as Ephemera lineata, Ephoron virgo, Ephemerella notata, Heptagenia coerulans and of the stonefly Leuctra hippopus confirmed the gradual water quality improvement. Chironomidae with 50 taxa are considered the most diverse taxonomic group of the zoobenthos. The presence of the New Zealand snail Potamopyrgus antipodarum, the North-American flatworm Planaria tigrina and the caddis Ay Hydropsyche incognita (described recently) is very interesting from a faunistic point of view. The water quality, based on the registered taxa, is characterised by beta-mesosaprobity at almost all the study sites except the Morava and Vah rivers and the Danube downstream of the Bratislava-Slovnaft oil refinery, where water quality reached alpha-mesosaprobity. Diversity and equitability indices were the highest in the Vah and Ipel' tributaries.