Sources and sinks of plastic debris in estuaries: A conceptual model integrating biological, physical and chemical distribution mechanisms

Micro- and macroplastic accumulation threatens estuaries worldwide because of the often dense human populations, diverse plastic inputs and high potential for plastic degradation and storage in these ecosystems. Nonetheless, our understanding of plastic sources and sinks remains limited. We designed conceptual models of the local and estuary-wide transport of plastics. We identify processes affecting the position of plastics in the water column; processes related to the mixing of fresh and salt water; and processes resulting from the influences of wind, topography, and organism–plastic interactions. The models identify gaps in the spatial context of plastic–organisms interactions, the chemical behavior of plastics in estuaries, effects of wind on plastic suspension–deposition cycles, and the relative importance of processes affecting the position in the water column. When interpreted in the context of current understanding, sinks with high management potential can be identified. However, source–sink patterns vary among estuary types and with local scale processes. [Display omitted] •Plastic pollution affects estuaries, but knowledge of sources and sinks is limited.•We designed conceptual models of the local and estuary-wide transport of plastics.•Knowledge gaps are identified and first management points suggested.•Sinks with high management potential can be identified at estuary-wide scale•Source-sink patterns vary among estuary types and with local scale processes.