The aim of the study was to test the significance of the EPT index in the water quality assessment of three types of water bodies in hilly and mountainous region of Serbia. The aquatic macroinvertebrate community was dominated by the group of insects, of which 95 taxa represent the EPT group. We compared the obtained values of biological indices used for the assessment of water quality according to the national legislation with the overall status assessment represented by the ecological quality classes (EQC). The results of the Spearman correlation test showed a negative correlation of EQC with the EPT index, BMWP score, H′, total number of taxa and number of sensitive taxa, while a positive correlation was observed for the values of SI and Tubificinae %. The values of EQC and biological indices were subjected to principal component analysis (PCA). The results showed that the parameters that contributed most to the differences were the EPT index, the BMWP score and the number of sensitive taxa. The results indicate that the EPT index is an excellent indicator of changes in water quality and an important tool for the ecological categorization of water bodies in mountain regions.

The development of nonlethal methods for the monitoring of environmental contamination is essential to minimize the negative effects on studied species and communities. Fish scales and fin clips can be used as nonlethal indicators of water quality given that they are in direct contact with the environment and can accumulate high concentrations of metals and trace elements. Fin clipping causes minimal harm to fish and it does not affect fish growth or survival. In this study, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn concentrations were measured by inductively-coupled plasma mass spectrometry (ICP-MS) in scales, fins, and muscle of common bream (Abramis brama), white bream (Blicca bjoerkna), wels catfish (Silurus glanis), northern pike (Esox lucius), and pikeperch (Sander lucioperca) from the Danube River. The analysis showed a positive correlation for Hg between scales and muscle in pikeperch. Anal fin and muscle were positively correlated in white bream for Hg, in wels catfish for Cu, and in northern pike and pikeperch for As. The results suggest that scales and fins have a potential to be used as indicators of muscle tissue contamination with As, Cu, and Hg, depending on species' ecological traits.

In this study, the activity of oxidative stress parameters superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and glutathione S-transferase (GST), as well as the concentrations of vitamin E (Vit E) and SH groups in the digestive glands and gills of freshwater mussels Unio pictorum and Sinanodonta woodiana from the Sava River in Serbia were investigated. These parameters were determined in native and invasive mussels under the same environmental conditions. The activities of GSH-Px and GR and the concentration of Vit E were significantly higher in the digestive glands of the autochthonous species U. pictorum than in the invasive species S. woodiana, while the CAT activity and the concentration of SH groups were lower. In the gills of U. pictorum, GSH-Px activity and Vit E concentration were significantly higher, while CAT, GST, and SH groups were lower. Principal component analysis (PCA) showed that oxidative stress parameters were strictly tissue- and species-specific. In addition, integrated biomarker response (IBR) showed a combined response of enzymatic and non-enzymatic oxidative stress parameters depending on the tissue or species studied, indicating different metabolic activities and behaviors of an autochthonous versus an introduced bivalve species.