Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Oceanography

Advisor

Margaret Estapa

Second Committee Member

Lee Karp-Boss

Third Committee Member

Kara Lavender Law

Abstract

Numerous studies on the transport and fate of plastic have alluded to a size-specific mechanism for removing microplastics (plastics below 5mm in diameter) from the epipelagic. Plastics like polyethylene and polypropylene which are less dense than seawater during manufacturing and use have been found throughout the water column and even in seafloor sediments. However, the mechanism for their vertical transport is poorly understood. This project calculates the vertical flux of microfibers during the 2021 EXPORTS North Atlantic campaign and captures the decline of the spring bloom from the base of the mixed layer to the mesopelagic by utilizing both lagrangian and semi-lagrangian sediment traps to capture sinking particles. In addition to creating a flux profile of both microfibers and particulate organic carbon, polyacrylamide gels were attached to the base of sediment trap tubes and used to visually observe the relationship between microfibers and organic aggregates. Laboratory experiments validated the use of gels in microfiber collection by showing that the density gradient of the gels does not disaggregate fibers from marine snow and artificially made aggregates with polyester and polypropylene microfibers remain intact. The data shown by the gels demonstrate little correlation between microfibers and particulate organic carbon, which agrees with the flux profile comparisons. These new methods of microplastic collection for vertical flux measurements allow for direct visualization of plastic in organic particles which can aid to validate theories of the transport of plastic by the biological carbon pump.

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