Short-term microplastic exposure triggers cellular damage through oxidative stress in the soft coral Coelogorgia palmosa

Microplastics are a persistent and ubiquitous source of pollution in the marine environment, representing a severe threat to tropical coral reefs. The effects of microplastics on reef-building (hard) corals have been documented (interference with normal digestion process, polyp retraction, oxidative stress, impairment of the photosynthetic machinery, bleaching). However, the impact of microplastics on soft corals, the second most abundant benthos of tropical reefs, remains to be thoroughly studied. In this work, we analysed the effects of a short-term microplastic exposure on the cellular physiology of the soft coral Coelogorgia palmosa. We found that samples exposed to >50 mg l−1 of microplastic showed significant increase in the activities of the antioxidant enzymes glutathione reductase, catalase, and superoxide dismutase, suggesting a rise in oxidative stress. Furthermore, exposure to microplastics increased lipid peroxidation, indicating oxidative damage. Overall, our results show that similar to hard corals, microplastic ingestion causes oxidative stress and cellular damage in soft corals. Our study provides a first assessment of physiological effects of microplastic exposure on the soft coral, Coelogorgia palmosa, highlighting the need for further investigations about these contaminants and their influence on marine benthic fauna. Such information is crucial to understand how different reef organisms respond to microplastic pollution and who the ecological winners or losers will be in an increasingly polluted marine environment. Key policy highlights The effect of microplastic contamination at the cellular and molecular level has never been investigated before in alcyonacean corals. Concentrations of 50–70 mg l−1 of polyethylene caused significant rise in oxidative stress in Coelogorgia palmosa after 48 h. After 48 h exposure to 50 mg l−1 significant oxidative damage was recorded. No significant modulation in the expression of the cytoprotective protein Hsp60 was observed after exposure to microplastics.