As bivalves are widely used as bioindicators of pollution in freshwater, marine and estuarine ecosystems, they are known to provide a time integrated indication of environmental contamination as well as reliable information on the ecosystem state under anthropogenic influence Therefore, transplants with mussels (Sinanodonta woodiana Lea, 1834) were applied to investigate the water quality in standing water bodies by applying sensitive biomarkers. Changes in the activity of the antioxidant enzymes such as cholinesterase (ChE), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were used to study the oxidative stress in the bioindicators.