From Shoreline to Seafloor: Investigation into the Distribution of Marine Plastic Debris Around Narragansett Bay of Rhode Island

Abstract:

Marine debris is a growing environmental issue. In particular, the exponentially increasing production of plastic has resulted in more pollution entering the ocean, but transport pathways need investigation. Microplastic particles (< 5mm) are of particular concern ecologically, while mesoplastics (5-25 mm) and macroplastics (>25 mm) are visually impactful and can break down to finer fragments. Previous work suggests coastal sediments may be an important sink. As part of a broad university initiative, an investigation into the distribution of plastic particles in Rhode Island marine environments is being conducted. The Narragansett Bay is a large estuary with variable shoreline and seafloor morphology, complex patterns of substrates, and a history of textile manufacturing and plastic use, providing an ideal laboratory to explore the distribution of marine microplastics.

This in-progress study is examining sediment along shorelines and on the seafloor from bay head to mouth – from Providence to Point Judith. At numerous sites, three shore-perpendicular transects are being visually surveyed from upland to subtidal areas. Photograph stations and sediment samples are being analyzed to quantify the distribution of microplastics within the coast of the Narragansett Bay. Additionally, coring is planned to examine the distribution of microplastics in bottom sediments. Initial analyses on subaerial beach transects in late spring 2020 demonstrated that the dominant plastic particles are microplastics (<5 mm) and mesoplastics (5-25 mm), with greatest abundance observed in the upper bay, proximal to Providence. Highest counts of plastics were measured at along the high-tide and dune/vegetation lines. More sampling and analyses are underway.