Benthic communities in relation to environmental factors in small high mountain ponds threatened by air pollutants.

Hydrobiological investigations of ponds situated above the timber line in the Tatra Mountains (Poland) were carried out. These water bodies are fed mainly by rainfall and melting snow. Some of them are temporary while others are permanent and show seasonal varia- tions in chemical properties (e.g. pH 4.6-5.0 to 6.8-7.7). The structure of the algal communities differed in particular ponds, depending on the water pH and its seasonal changes. Moreover, there are differences in the composition of the macro-invertebrate communities between particular ponds, but they were not affected by the water acidification occurring mainly during the snow-melting period. The present investigations show that the impact of acid precipitation on biocenoses living in high mountain water bodies (Tatra Mts) is not clearly evident. [ABSTRACT FROM AUTHOR]