EFFECT OF SEA SURFACE TEMPERATURE ON CATALASE AND GLUTATHIONE S-TRANSFERASE ACTIVITIES IN SCLERACTINIAN CORAL Acropora digitifera FROM PULAU BIDONG, TERENGGANU

Natural exposure of coral reefs to stressors induces an oxidative stress response. In Malaysia, biomarkers used to assess this response are limited. This study investigated the activities of the antioxidant enzymes glutathione S-transferase (GST) and catalase (CAT) in the scleractinian coral Acropora digitifera across three separate sites in Pulau Bidong, Terengganu during March, May, July, and September 2018 to understand the variations in these enzyme activities. Fragments of corals were airbrushed to remove tissue, disrupted to release cytosol, and the enzyme activities were assayed. The result demonstrated variation in GST activities with the highest level in May (p < 0.05) and in contrast, there was no significant difference in CAT activities between different sampling months and sites (p > 0.05). In addition, A. digitifera collected in Pantai Pasir Cina (PPC) showed the highest antioxidant activities for both enzymes (GST, 19.6 ± 5.10 µmol/min/mg protein; CAT, 14.6 ± 3.40 U/mg protein), suggesting corals in this location are responding to oxidative stress. These values are lower than previously reported for A. digitifera in Pulau Bidong, indicating a stable and adequate baseline level of antioxidant enzyme activities. These findings provide valuable insights and crucial information for future reference.