Assessing the effects of Thiram to oxidative stress responses in a freshwater bioindicator cladoceran (Daphnia magna)

Thiram (TMTD) is able to induce antioxidant defense and oxidative stress in different organisms. Moreover, Thiram can act as a prooxidant resulting in the formation of Reactive Oxygen Species (ROS). To our knowledge, this is the first study assessing the oxidative stress induced by Thiram in the cladoceran Daphnia magna. At present, literature focus on the determination of toxicity in vertebrate organisms or cells, however, very few studies were interested to evaluate Thiram's effects in aquatic organisms such as cladoceran. To assess these effects, antioxidant GSH content, CAT and GST Enzyme activities, cellular damages and lipid peroxidation indicators (MDA) were evaluated as oxidative stress biomarkers. Our results showed that acute Thiram exposure resulted in significant biochemical responses, demonstrating that Thiram induced oxidative damage. Indeed, following exposure to Thiram, we noticed an intracellular (GSH) depletion, associated with a marked increase of lipid membrane peroxidation as shown by high (MDA) production. Moreover, a dose-dependent induction of antioxidant key Enzymes (CAT) and (GST) was found which led to an oxidative stress and finally death of Daphnia magna.