Fluvial geomorphology proposes the methodology of cognition and assessment of the riverine landscape and points to the possibilities of exploitation of its results in hydrobiological research. Habitat structure of two reaches of the Drietomica brook (Biele Karpaty Mts, Slovakia) was assesed at level of morphological and morphohydraulic units in the sense of the River Morphology Hierarchical Classification (RMHC)). Physical habitats were described by flow hydraulics and substrate properties as directly measured variables (current velocity, depth, substrate size) and related variables (flow type, Froude and Reynolds numbers). According to the shear stress (expressed by Fr and Re), the morphological units were divided into two main groups -with low shear stress -pools, glides, edgewaters, bar nooks and bars; with high shear stress -riffles, runs, rapids and scours; characterized also by different Ephemeroptera, Plecoptera and Trichoptera (EPT) communities. The EPT communities were analyzed in relation to the morphological, hydraulic and substrate characteristics of the stream channel. The main environmental gradient responsible for the variation in EPT fauna was found using Principal Component Analysis and was related to gradient of flow in term of current velocity and other hydraulic attributes covered by Fr and Re numbers. The EPT communities (by means of abundance, feeding types, current, microhabitat and zonation preferences) showed preferences for different morphological units, flow type and current velocity. Depth and substrate grain size showed only weak relation to EPT communities.

Macroinvertebrate communities at 16 sites in Cerova´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.

A multimetric assessment system was developed to determine the ecological status of two types of stream in the Carpathian ecoregion following the requirements of the WFD. The organic pollution gradient was defined using Canonical Correspondence Analysis. Classification based on physical, chemical and biological data divided the tested sites into two stream types with subsequent grouping into several ecological quality classes. From all the metrics tested, 17 for the East Carpathian streams and 15 for the West Carpathian streams, from seven metric categories, were included in the resulting multimetric index. Different kinds of response to degradation (linear, unimodal, exponential) were observed. The Saprobic index (Zelinka and Marvan), Rheoindex (Banning, with abundance classes) and Index of Biocenotic region, showed the best discriminatory ability for both stream types.