Analysis of multiple-pressure pattern in rivers and its effects on the structure of macroinvertebrate communities

Natural and anthropogenic factors form stream macroinvertebrate communities depending on their combination, intensity, and spatial pattern. The study aimed to identify macroinvertebrate indicators that respond to land cover, hydromorphology, and wastewater releases individually and to their multiple-pressure pattern. Environmental and macroinvertebrate data from 36 sites were used in the study. Pressure parameters representing hierarchy of their complexity and spatial scale were included in analyses. Correlation analyses were used for evaluation of relationships among pressure characteristics and also pressure–macroinvertebrate relationships. The pressure-based and biological classification of sites was compared and indicator taxa were identified. The arable land in the sub-corridor extending 2–10km upstream of an investigated site was the main pressure factor influencing the structure of macroinvertebrate communities in the studied streams. The biological effects of small-scale land cover were followed by catchment-scale land cover and hydromorphology. Almost no association of macroinvertebrates with the risk of point source pollution were detected. Classifications based on pressures and community composition corresponded only by the separation of most degraded sites from others. Among the macroinvertebrate indicators characterizing the severe impairment threshold, chironomids and oligochaetes dominated. Different responses of macroinvertebrates to hydromorphological degradation were observed under conditions of high small- and large-scale agricultural pressures (decrease in macroinvertebrate evenness and increase in oligochaete taxa richness, respectively). Linking biological indicators to pressure components and their combinations improves the efficiency of conservation and restoration strategies applied in fluvial ecosystems.