Acute toxicity assessment of sunscreen products in corals using single-polyp metabolomics

While UV filters (UVFs) in sunscreens are effective in preventing skin cancer, their potential impacts on coral reefs remain a concern. However, most prior work has evaluated single UVFs or solvent-prepared mixtures that do not reflect the leaching behavior of real-world products into marine ecosystems. Here, we performed a product-level assessment that preserves realistic exposure states and combine it with single-polyp metabolomics that can be performed with or without zooxanthellae. By testing products that reproduce realistic exposure states with solvent-prepared UVFs, we captured formulation-dependent differences in UVF leaching and acute polyp responses. We observed that only ZnO induced metabolomic changes consistent with glutathione-related oxidative stress and glycolytic activation in aposymbiotic polyps, whereas no such changes were observed for ZnO-containing products. These differences in acute toxicity are consistent with limited Zn²⁺ leaching from product matrices into seawater, indicating that sunscreen products can effectively suppress zinc ion leaching into seawater. These findings highlight the importance of toxicity assessments that explicitly account for environmental exposure conditions.