riverine metagenome Targeted Locus (Loci)

The hard and buoyant surface of microplastic is a novel habitat that can select for unique microbial communities in rivers, especially downstream of wastewater treatment plant (WWTP) point-sources. Microplastic may transport microbes downstream, but there are no longitudinal assessments of microplastic-associated biofilm communities. We measured microplastic in an urban river that receives effluent from a large WWTP. We measured microplastic in surface and benthic habitats at 50 m upstream of the effluent outfall, and at 50, 305, 1115, and 1900 m downstream. We used high-throughput sequencing to measure bacterial communities on microplastic from surface and benthic habitats, and compared them to bacterial communities from seston, water, and sediment. Microplastic-attached bacterial communities were distinct in taxonomic composition from communities from natural habitats of water, seston, and sediment. Composition of microplastic-attached communities supports domestic wastewater as a point source of microplastic, but shifts in microplastic community composition with distance from the WWTP suggests succession to a 'stream-like' bacterial community and away from a 'WWTP-like' bacterial community.