The hierarchy of multiple stressors’ effects on benthic invertebrates: a case study from the rivers Erft and Niers, Germany

Abstract Background A variety of anthropogenic stressors influences the ecological status rivers wordwide. Important include elevated concentrations nutrients, salt ions, heavy metals and other pollutants, habitat degradation flow alteration. Some tend to remain underrepresented in multiple-stressor studies, which particular is apparent for micropollutants (e.g. pesticides, pharmaceuticals) alterations regime. This case study analysed compared effects 19 different stressor variables on benthic macroinvertebrates two German Erft Niers (Federal State North Rhine-Westphalia, Germany). The were assigned four groups (physico-chemical stress, mixture toxicity 42 micropollutants, hydrological alteration morphological degradation) put into a hierarchical context according their relative impact macroinvertebrate community using redundancy analysis subsequent variance partitioning. Results results suggest strong unique effect physico-chemical yet at same time reveal also joint variables. Morphological showed subordinate effects. Notably, only minor share explained was attributed these specific catchments. Conclusions hierarchy indicates that management measures improving still need address water quality issues both rivers. stress might imply common source catchment areas: lignite mining drainage, urban area effluents wastewater treatment plants. findings point important role regime, often unconsidered hydro-morphological surveys.