Emergence of specialized plastic-degrading enzymes within highly dynamic coastal oceans

Freshwater inflow strictly controls the abundance of microplastic within coastal ecosystems. Sundarbans, the world’s largest contiguous mangrove ecosystem, faces the northern coastal Bay of Bengal and forms a source of anthropologic matter, including microplastics, to the ocean. In-depth spatial and temporal studies during a long-term monitoring program, SBOTS, indicated presence of high abundance of microplastics. Alongside, nearly 748 plastic-degrading enzymes (PDEs) hits were identified. These PDEs are capable of breaking down 17 types of polymers, both natural and synthetic types and notable seasonal variation. A diverse group of bacteria appear to house these PDEs within their genomes. Further genome-scale analyses revealed high numbers of heavy metals resistance genes (MRGs) and antibiotic resistance genes (ARGs). Co-occurrence network analysis suggested potential co-selection of plastic-degrading genes, MRGs and ARGs. Such co-occurrence patterns will have strong implications for disease dissemination within highly populated estuaries. Goals for SDG1 and SDG14 would both strongly be impacted should plastic pollution drive disease dissemination within high populated ecosystems such as the Sundarbans. It is thus imperative to further study such correlation patterns to understand ecosystem-level responses to microplastics within the changing ocean.