Estuarine plastisphere as an overlooked source of N(2)O production

“Plastisphere”, microbial communities colonizing plastic debris, has sparked global concern for marine ecosystems. Microbiome inhabiting this novel human-made niche has been increasingly characterized; however, whether the plastisphere holds crucial roles in biogeochemical cycling remains largely unknown. Here we evaluate the potential of plastisphere in biotic and abiotic denitrification and nitrous oxide (N(2)O) production in estuaries. Biofilm formation provides anoxic conditions favoring denitrifiers. Comparing with surrounding bulk water, plastisphere exhibits a higher denitrifying activity and N(2)O production, suggesting an overlooked N(2)O source. Regardless of plastisphere and bulk water, bacterial and fungal denitrifications are the main regulators for N(2)O production instead of chemodenitrification. However, the contributions of bacteria and fungi in the plastisphere are different from those in bulk water, indicating a distinct N(2)O production pattern in the plastisphere. These findings pinpoint plastisphere as a N(2)O source, and provide insights into roles of the new biotope in biogeochemical cycling in the Anthropocene.