Mangroves are facing varying degrees of anthropogenic stresses due to overexploitation, urbanization, discharge of industrial effluents, domestic sewage, and pesticide residues from agricultural land. These anthropogenic activities result in the accumulation of a wide range of toxic xenobiotic compounds in the ecosystem, microplastics being one of them. The present study investigated the abundance and composition of microplastics in surface water of Indian Sundarbans along with the application of metagenomic approach in exploring the microbial community structure and mining the genes involved in the biodegradation of various xenobiotics. The world's largest contiguous mangrove forest, Sundarbans, is a UNESCO world heritage site and a Ramsar site. Sundarbans is shared between Bangladesh and India, which are among the top mismanaged plastic waste generating nations and are discharging plastic waste downstream through rivers and coasts, making the Sundarbans a cesspit for plastic waste. The observed mean abundance of microplastics is 22.27±11.8 Particles/Liter in monsoon and 14.52±7.97 Particle/Liter in post-monsoon. Fiber constituted the major portion amongst the different forms of microplastics including fragment, microbead and foam. Moreover, chemical characterization of microplastics revealed polypropylene as the most abundant type of polymer. Mangroves are the hotspots for microbial diversity and harbor microbiota involved in producing a variety of degrading enzymes, antibiotics, etc. Metagenomic profiling of the surface water samples reported Proteobacteria as a dominant phylum, with Bacteroidetes and Firmicutes the second-most in prevalence. The functional profiling revealed the presence of enzymes involved in the biodegradation of xenobiotic compounds such as Benzoate compounds, Nitrotoluene, Chlorocyclohexane, and Chlorobenzene, Polycyclic aromatic hydrocarbons (PAH), xylene, bisphenol, and Dioxin. The results also showed the presence of potential genes associated with the biodegradation of different types of plastic polymers such as PHA (Polyhydroxyalkanoates), PBAT (Poly(butylene adipate-co-terephthalate)), PET (Polyethylene terephthalate), LDPE (Low-density Polyethylene), PS (Polystyrene), Nylon. The study not only fills up the scientific gap in our knowledge regarding the microplastic pollution in Indian Sundarbans but also provides an insight into the rich source of the gene pool, which is actively involved in the degradation of various xenobiotic compounds.   

Primary Presenter: Nirupama Saini, Indian Institute of Science Education and Research Kolkata (nirupamasaini15@gmail.com)

Authors:

Nirupama Saini, Indian Institute of Science Education and Research Kolkata  (nirupamasaini15@gmail.com)

Punyasloke Bhadury, Indian Institute of Science Education and Research Kolkata  (pbhadury@gmail.com)