Macroinvertebrate assemblages in conditions of low-discharge streams of the Cerová vrchovina highland in Slovakia

AbstractMacroinvertebrate communities at 16 sites in Cerová vrchovina highland were sampled in 2000–2001 to analyze the influence of environmental factors on community structure with emphasis on Ephemeroptera, Plecoptera and Trichoptera (EPT). The extreme hydrological conditions of this area determine the macroinvertebrate community structure. Totally, 16 Ephemeroptera, 8 Plecoptera and 36 Trichoptera taxa were found. Predators of the families Perlidae, Perlodidae and Chloroperlidae (Plecoptera) were absent. The record of Protonemura aestiva is the second one in Slovakia. Ephemeroptera were represented mainly by rheophilous taxa. A rare lowland species Baetis tracheatus was found, known previously just from West Slovakia. Trichoptera were mainly represented by submontane rheophilous taxa. Species preferring low currents or backwaters from the family Limnephilidae were also recorded. Altitude and dissolved oxygen content were found to be the most important environmental variables determining the EPT community structure. Six types of streams were distinguished by the results of multivariate analysis, taxonomic composition and metric values. They belong to two main types: (1) EPT communities of the natural streams and (2) EPT communities of disturbed streams, where two types of stressor were identified–organic pollution and low discharge. A similarity between EPT communities of organically polluted streams and streams with very low flow was discovered. Values of biotic indices decreased in summer. The most diversified communities were found in the spring during higher water levels and better oxygen conditions