Use of Desmidiales flora for monitoring rivers: a case of South-Hungarian waters
The Desmidiales flora can be a very good indicator of ecological status of rivers and other water-bodies. Desmids found in rivers show the connections of the rivers with their dead- and sidearms. This seems especially important in determining the ecological status of slowly streaming waters (mainly lowland's rivers, canals, dead- and sidearms of rivers). The sample collection from these biotops cannot be omitted if we liked to know about their status. In the present study, a Dutch-system (Coesel 1998) was applied to the investigated South-Hungarian waters. The results of the rivers were compared to that of dead- and sidearms, lakes situated on these areas. The essence of the applied method is the determination of the Nature Conservation Value (NW by Coesel) based on desmid assemblages. The parameters chosen to determine NW are diversity (species richness), rarity (occurrence of rare taxa) and maturity (presence of species indicative of ecosystem maturity). The comparison of 15 water-bodies belonging to different types (canals, side-arms, dead-arms and lakes) is presented. There are 6 water-bodies that have a high natural conservation value according to their desmid flora. Experience shows that this method is well usable for Hungarian waters, too. In the present study, there are some suggested modifications for the indicator value based on the occurrences of the determined Desmidiales taxa in Hungary.