Antioxidant defense of Ephemera danica larvae (Ephemeroptera: Ephemeridae) − seasonal and longitudinal impact of the trout farm

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This study involves investigation on the seasonal and longitudinal effects of the trout farm on the Crnica River on the chemical composition of water and sediment, structure, and composition of the macrozoobenthos communities and molecular biomarkers of oxidative stress, such as activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and the amount of total glutathione (GSH) in larvae of Ephemera danica (Müller 1764). To analyze the changes in the composition of the macrozoobenthos community caused by fish farm effluents, several macrozoobenthos indices were used. The potential impact of trout farm effluents on the macrozoobenthos community was evident at the CR2 sampling site, where the saprobic index (SI) reached its highest value and the BMWP (Biological Monitoring Working Party) score was at its lowest. This indicates that the fish pond had negative effect on water quality and reduced the diversity of the macrozoobenthos community. All components of antioxidant defense showed minimum activity in autumn and maximum in summer. The most sensitive biomarker to the effects of the trout farm effluents was the change in the GPx activity. This biomarker showed higher sensitivity in relation to most sensitive macrozoobenthos indices − SI, BMWP, and MBMWPPO (Modified Biological Monitoring Working Party Present Only). Seasonal changes in abiotic factors were more pronounced than changes in abiotic factors along the sites, which we consider to be influenced by the fish pond and refer to as longitudinal changes. Therefore, the seasonal changes in environmental abiotic factors had a greater impact than the fish farm on the examined biomarkers and the structural and compositional parameters of the macrozoobenthos communities. Regarding seasons, most pronounced farm effects could be seen in autumn, when synergistic impact of pollutants, such as NO2– and NH3, and abiotic parameters of water and sediment (Cr and Ni) had a negative effect on the macrozoobenthos community, but primarily on the components of the antioxidant defense in E. danica which caused decrease in the number of specimens in autumn, as much as 10-fold less than in summer.