Investigations on the responses of antioxidant enzymes in freshwater mussels (Unio stevenianus Krynicki, 1837) exposed to various pollutants from Karasu River (Van, Türkiye)

Many substances of domestic, industrial and agricultural origin cause environmental pollution. Aquatic environments are regions where pollutants released into nature without treatment eventually collect and accumulate. These natural aquatic environments provide habitat for many vertebrate and invertebrate organisms. One of these organisms is the freshwater mussel, which come forward with its ecological importance. Mussels are organisms feed by fixing themselves to an object and filtering water. They reflect the pollution composition of their environment due to their fixed lifestyle and feeding regime. Therefore, they are frequently used in environmental monitoring and follow-up studies. The aim of this study is to determine the biochemical responses caused by pollutants to which freshwater mussels (Unio stevenianus) from the Karasu River are exposed in the natural environment. In this context, mussel samples were collected from the Arısu and Zeve regions of the river. Morphometric characteristics were determined in the samples. Supernatants obtained from gill tissue of U. stevenianus were used in biochemical analyses. Superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), reduced glutathione (GSH) and total protein (TP) measurements were performed in the samples. Absorbance values were determined by spectrophotometric method. The calculated values for mussels from Arısu and Zeve regions were found as 1015.88±43.59 and 974.53±28.74 U/g protein for SOD, 7.13±0.92 and 6.13±1.83 nmol/g protein for CAT, 38.14±7.94 and 43.33±5.59 nmol/mg protein for GST, 0.99±0.13 and 0.76±0.07 U/mg protein for GR, 48.63±4.11 and 58.23±4.39 U/g protein for GSH-Px, 94.27±19.56 and 79.66±13.3 nmol/g protein for MDA, 3.7±0.72 and 3.21±0.4 µmol/mg protein for GSH, and 10.46±0.47 and 10.13±0.24 mg/mL for TP, respectively. It was determined that enzymatic and non-enzymatic antioxidant values changed between sampling region, but this change was not significant (P0.05). As a result, examining freshwater mussels in terms of antioxidant defense system parameters seems to be a useful and accurate approach in monitoring the pollution status of streams. Additionally, it would be appropriate to conduct subsequent studies to determine the accumulation that may occur in mussel tissue as a result of exposure to different substances.