Microplastic in two South Carolina Estuaries: Occurrence, distribution, and composition

Highlights: • First study to survey microplastic contamination in Southeastern, U.S. estuaries • Microplastics were found in the intertidal sediment and sea surface microlayer of each estuary. • Fibers were the most abundant particle type recovered from the sea surface microlayer. • Black fragments were the most abundant microplastic particle in both estuaries. • Black fragments in such high abundance have not previously been reported. - Abstract: Here we report on the distribution of microplastic contamination in two developed estuaries in the Southeastern United States. Average concentration in intertidal sediments of Charleston Harbor and Winyah Bay, both located in South Carolina, U.S.A., was 413.8 ± 76.7 and 221.0 ± 25.6 particles/m², respectively. Average concentration in the sea surface microlayer of Charleston Harbor and Winyah Bay was 6.6 ± 1.3 and 30.8 ± 12.1 particles/L, respectively. Concentration in intertidal sediments of the two estuaries was not significantly different (p = 0.58), however, Winyah Bay contained significantly more microplastics in the sea surface microlayer (p = 0.02). While microplastic concentration in these estuaries was comparable to that reported for other estuaries worldwide, Charleston Harbor contained a high abundance of black microplastic fragments believed to be tire wear particles. Our research is the first to survey microplastic contamination in Southeastern U.S. estuaries and to provide insight on the nature and extent of contamination in these habitats.