Effects of UV filters with potential mitigation of acute ZnO toxicity by hydrophobic coating on a coral, Acropora digitifera

Abstract

The components of sunscreen products released into the oceans have raised concerns over their possible adverse effects on corals in nearshore areas, leading to the ban of some sunscreen products and the use of alternative components. The aim of this study was to examine the impacts of seven major sunscreen components; ethylhexyl methoxycinnamate (EHMC), octocrylene (OC), oxybenzon-3 (BP-3) , butyl methoxydibenzoylmethane (BMDBM), terephthalylidene dicamphor sulfonic acid (TDSA), zinc oxide (ZnO) and hydrophobically-coated ZnO on the survival of a scleractinian coral species Acropora digitifera along with the assessment of photochemical efficiency of symbiotic dinoflagellates within the host tissues. No significant effects on survival and photochemical efficiency were observed within 5 days of high dose (1 mgL^-1) exposure to the 6 sunscreen ingredients. However, acute mortality was observed under ZnO exposure in a concentration-dependent manner (0.01-1.0 mgL^-1), whereas hydrophobically-coated ZnO didn't cause such mortality. The results of this study suggest that the direct and acute impact of ZnO on corals can be mitigated with an appropriate hydrophobic coating while maintaining similar sunscreen efficacy.