Microplastic degradation mediated by coral microbiome

Plastic pollution represents a global threat to the marine environment, with 5 to 13 million metric tons of plastic waste entering the ocean every year. These plastics are usually fragmented into small pieces due to the action of UV light and mechanical impacts, leading to a ubiquitous distribution of microplastics in the ocean. Although plastic pollution remains a critical issue, plastic waste in the ocean can be colonized and degraded by microorganisms; these biofilms are collectively referred to as the ‘plastisphere’. Despite the fact that several studies have reported seawater microorganisms involved in plastic degradation, none have investigated these processes in coral microbiomes. Thus, the main aim of this study was the analysis of the interactions between a microplastic polymer commonly found in the marine environment (polyethylene) and prokaryotic members of the coral microbiome. Individuals of two coral species (Acropora cervicornis and Siderastrea siderea) were exposed to different concentrations of polyethylene microbeads. Coral mucus, tissue and skeleton were subjected to various types of microbiological and molecular analyses (plate culture,16S rRNA Sanger and Illumina sequencing, qPCR) to assess the capability of their microbiome to degrade microplastic, to look for genes codifying for enzymes capable of PE degradation and also to observe shifts in the prokaryotic communities. Initial results highlight a significant capability of different prokaryotic taxa present in the coral microbiome to exploit PE as a carbon source. The identification of prokaryotic taxa capable of plastic degradation in corals represents an important milestone, with practical applications, that could elucidate naturally-evolving mechanisms used by marine organisms to cope with the effects of anthropogenic pollution.