Oysters, known for their environmental sensitivity, are potential bioindicators of stress in aquatic ecosystems. This study investigates the influence of environmental stressors, including salinity, temperature, and dissolved oxygen, on the enzymatic activities of Glutathione S-transferase (GST) and Catalase (CAT) in the gills and digestive glands of the slipper oyster, Magallana bilineata. Monthly sampling was conducted at Setiu Wetland, Terengganu (Malaysia), during the monsoon. Significant monthly variations were observed in temperature (p