EFFECTS OF MICROPLASTIC EXPOSURE ON PHYSIOLOGICAL AND ANTIOXIDANT RESPONSES OF REEF-BUILDING CORAL POCILLOPORA DAMICORNIS

Abstract

Microplastic pollution has emerged as a major environmental concern in marine ecosystems due to its persistence, widespread distribution, and potential harmful effects on aquatic organisms. Coral reefs are particularly vulnerable to environmental stressors, yet limited information is available regarding the physiological and antioxidant responses of reef-building corals to microplastic exposure. Therefore, the present study was conducted to evaluate the effects of microplastics on the physiological and antioxidant responses of Pocillopora damicornis under controlled laboratory conditions. Healthy coral fragments of Pocillopora damicornis were obtained from a commercial marine aquarium supplier and acclimatized prior to experimentation. Corals were exposed to different concentrations of polyethylene microplastics, including 0 mg/L (control), 10 mg/L, 50 mg/L, and 100 mg/L for a period of six weeks. Physiological parameters such as growth performance, polyp activity, bleaching response, and chlorophyll content were evaluated. Antioxidant and oxidative stress biomarkers including reactive oxygen species (ROS), superoxide dismutase (SOD), and catalase (CAT) activities were also analyzed. The results demonstrated that increasing concentrations of microplastics negatively affected coral physiology. Coral fragments exposed to higher microplastic concentrations exhibited reduced growth, decreased polyp extension, mild bleaching, and lower chlorophyll content compared with the control group. Furthermore, ROS production significantly increased in treated groups, indicating elevated oxidative stress. Antioxidant enzyme activities, including SOD and CAT, also increased progressively with increasing microplastic concentrations, suggesting activation of cellular defense mechanisms against oxidative damage. Although complete coral mortality was not observed during the experimental period, the findings indicated that continuous exposure to microplastics may gradually impair coral health and physiological stability. The present study concluded that microplastic pollution poses a significant threat to reef-building corals by inducing physiological disturbances and oxidative stress responses. This study provides preliminary baseline information regarding the effects of microplastics on corals and highlights the importance of reducing plastic pollution to protect coral reef ecosystems and marine biodiversity