Date of Award

12-10-2022

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Till J.J. Hanebuth

Second Advisor

Stefanie Whitmire

Third Advisor

George W. Hitt

Abstract

The global, rapid increase in plastic production is a widespread problem for coastal environments such as marshes that present favorable conditions for plastic retention. This study looked at the microplastic abundance within three previously unstudied South Carolina marshes located in Myrtle Beach, Murrells Inlet, and Waties Island. A comparison between the microplastic types and abundances between locations provided knowledge about the impacts of sediment composition (sand, silt, clay, and organic matter) on microplastic sequestration. This study also produced a novel microplastic extraction methodology for cohesive marsh sediment that used elutriation to effectively break apart aggregates prior to chemical digestion and density separation. The results of this study indicated that fine-grained sediments (< 63 μm) trapped more microplastics than coarser-grained sediments (> 63 μm). This was observed when the Myrtle Beach sample showed the most fine-grained sediment composition with 5 % clay, 38 % silt, and 57 % sand, and also yielded the highest quantity of microplastics with 174 red fibers, 262 blue fibers, and 100 other colored fibers extracted with a 95 % confidence to have not come from background contamination. The relationship between plastic type and sediment grain size ranges showed strong positive correlations (r ≥ 0.99) between blue (p ≤ 0.05), red (p ≤ 0.1), black (p ≤ 0.1), and other colored fibers (p ≤ 0.1) with a grain size range of 10-63 μm. Opposingly, blue (p ≤ 0.05) and other colored fibers (p ≤ 0.1) showed strong negative correlations (r ≥ -0.99) with a grain size range of > 63 μm. The data produced from this study now serves as a baseline dataset for future microplastic studies done in the marshes of Myrtle Beach, Murrells Inlet, and Waties Island, as well as studies working with cohesive material. In future studies, the implementation of FTIR spectroscopy could be used to confirm plastic polymer types and trace microplastics through sink-to-source approach.

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