Estuaries have been identified as hotspots of microplastic pollution because they are transitional zones where coastal freshwater and oceans converge. Microplastics (MP) are transported through estuaries by a dynamic series of forces such as surface flow and tides, which influence MP abundances and trends. The eastern oyster, Crassostrea virginica, is an estuarine bivalve known to ingest MP, resulting in negative impacts on organism physiology. I investigated MP pollution as a threat to C. virginica in a dynamic Florida estuary, the Indian River Lagoon (IRL), and determined there are both regional and small-scale spatial and temporal fluctuations in MP abundance. Tributaries were identified sources of MP, while inlets flush them out of the system. The south IRL is a hotspot for MP, where the St Lucie Estuary is the primary tributary. Throughout the IRL, fibers dominated MP and polyethylene terephthalate (PET) was the most abundant polymer type ( > 50%). Overall, C. virginica had a mean of 2.2 MP/individual and lagoon water had 1.5 MP/L. An in-situ biodeposition experiment revealed C. virginica of all sizes were able to egest environmental MP at a rate of 1 MP per 1 hour through feces, and 1 MP per 2 hours through pseudofeces. Oysters had a mean MP egestion efficiency of 62.1%, and 32.1% of oysters were able to egest all MP from their tissues within 2 hours. Smaller C. virginica were more efficient at egesting MP, and egestion efficiency decreased by 0.8% for every 1-g increase in tissue weight. Overall, I provide an argument that MP are ubiquitous in this hydrologically dynamic estuary in both the water and in a keystone, filter-feeding invertebrate. I estimate there are currently ~1.4 trillion microplastics in the Indian River Lagoon.
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Master of Science (M.S.)
College of Sciences
Length of Campus-only Access
Masters Thesis (Open Access)
Craig, Casey, "Correlations in Microplastic Abundance Between Water, the Eastern Oyster, Crassostrea virginica, and Their Biodeposits in a Dynamic Florida Estuary" (2021). Electronic Theses and Dissertations, 2020-. 488.