Abstract: 2-ethylhexyl-4-methoxycinnamic acid (EHMC) is an organic UV filter widely used in domestic sunscreen products. It is released into the ocean via human activities and accumulates in coral tissues, hastening coral bleaching. Biodegradation is an effective method for removing EHMC from coral, but little is konwn about its biodegradation in coral and its impact on coral microorganisms. To study the diversity of EHMC biodegradation in coral, we collected coral samples from Luhuitui, Sanya. These samples were enriched multiple times with EHMC as the sole carbon source to obtain EHMC-tolerance bacteria. High-throughput sequencing technology was used to analyze the composition and diversity of bacteria communities from enrichment samples. Besides, potential EHMC-degrading strains were isolated and identified from the enrichment through activity tests. High-throughput 16S rRNA gene sequencing revealed that the community divesity of Porites lutea, Favosites sp. and Acropora sp. was reduced under high concentration of EHMC. In contrast to their low abundance in the original coral samples, Agromyces, Paracoccus, Pelagibaca and Erythrobacter were the dominant genera after multiple enrichment with EHMC. Furthermore, a total of 60 bacterial strains were isolated from the EHMC-enriched samples. Based on 16S rRNA gene identification, these strains belonged to three phyla, three classes, six orders, eight families, thirteen genera and seventeen species. The main dominant genera among the cultivable bacteria were Bacillus, followed by Rhodococcus, Paracococcus, Exiguobacterium and Acuticoccus. Moreover, eight potential EHMC-degrading strains were selected through activity tests, belonging to Bacillus, Brevundimonas, Paracoccus, Acuticoccus, Phycicoccus, Rhodococcus and Mycolicibacterium, respectively. Previous studies have shown that Rhodococcus, Bacillus and Paracoccus were correlated with the biodegradation of aromatic compounds. This study illustrates the impact of EHMC on coral microbial communities and isolates potential EHMC-degrading bacteria, providing valuable information for coral resilience against organic UV filters. Additionally, it accumulates valuable bacterial resources for eliminating organic contaminants in coral by the subsequent construction of coral probiotic consortium.

Key words: coral, 2-ethylhexyl-4-methoxycinnamic acid, microbial diversity, mircobial degradation