Exploring the Hidden Threat of Organic UV Filters to Corals and Macroalgae in Coral Reef Ecosystem from Luhuitou, Sanya, China

The widespread presence of organic UV filters (OUVFs) in coral reef ecosystems has attracted increasing attention. This study analyzed the concentrations and compositions of OUVFs in corals, macroalgae, and sediments in the Luhuitou fringing reef ecosystem in Sanya, China. The detected OUVFs included benzophenones-1, -2, -3, and -8 (BP-1, BP-2, BP-3, and BP-8), 4-hydroxybenzoic acid (4-HB), octocrylene (OC), 4-methylbenzylidene camphor (4-MBC), and octyl dimethyl-p-aminobenzoic acid (ODPABA). The total concentrations (∑8OUVFs) in coral tissues and macroalgae were found to be 4.3–52.0 and 8.0–29.0 ng/g dry weight (dw), respectively. The bioaccumulation factors (BAFs) for BPs (including BP-1, BP-3, and BP-8) and OC in coral tissues were higher than those in macroalgae, while the BAFs for 4-MBC and ODPABA were relatively lower. Preliminary risk assessment results indicated that, in the worst-case scenario, more than 65 and 84% of coral samples had BP-3 concentrations exceeding the thresholds for causing coral larval bleaching and mortality, respectively. At the same time, 99% of the macroalgae samples showed ODPABA concentrations exceeding the thresholds related to their growth inhibition. Therefore, BP-3 and ODPABA posed significant ecological risks to corals and macroalgae, subsequently threatening the health and stability of the coral reef ecosystem.