2020 ESA Annual Meeting (August 3 - 6)

COS 153 Abstract - Microplastics in the American oyster, Crassostrea virginica, and their habitat

Stefanie L. Whitmire1, Stephen Borthayre2, Natalia Arbelaez2, C. Anna Toline3 and Jack Whetstone1, (1)Baruch Institute of Coastal Ecology and Forest Science, Clemson University, Georgetown, SC, (2)Clemson University, SC, (3)Ocean Programs, National Park Service
Background/Question/Methods

Studies indicate a pervasive presence of microplastic in the environment. Not only are they found floating in the ocean, they have been found in all types of habitats and organisms such as zooplankton, coral, and fish. Since plastic has the potential to adsorb contaminants, the risk to individual organisms and potentially food webs could have large implications. Oysters are important filter-feeders and a key component in many coastal environments in the eastern United States. Large rivers are known to carry microplastics from the watershed out to the ocean. This poses risks to the oyster communities found in the salt marshes surrounding large rivers. We focused on understanding the distribution of microplastic in the American oyster, Crassostrea virginica, and their habitat near the mouth of a large river system, the Savannah River. Collaborating with the National Park Service, we collected oysters and sediment from the tidal creeks and the river. Oysters were chemically digested to extract microplastics. Dried sediment samples were sieved to remove large debris and microplastics were separated from the sediment using density separation. Factors that might contribute to the distribution pattern were examined including currents, distance to the river channel, and wastewater treatment facilities.

Results/Conclusions

Microplastics were found in oysters and sediment at all locations. Oysters had an average of 4 pieces of microplastic/ g wet oyster weight in all locations. There were significantly more microplastics in the river sediment (225 pieces/kg sediment) compared to tidal creek sediment (150 pieces/kg sediment), with a tendency for microplastic abundance in sediment to increase closer to the mouth of the Savannah River. Fibers made up the majority of the microplastic counted, with sediment containing 55% and oysters containing 75% fibers. Microplastic pieces were more prevalent in sediment than oysters, and beads were not common in either. The presence of microplastics across the sampled area was anticipated given the ubiquitous nature of microplastic pollution. The high concentrations seen in the sediments gives a long term perspective of the microplastic burden in a large river estuary system. Hopefully microplastics in sediment will stay buried and out of circulation except in episodes of resuspension. Oysters are filtering water (and suspended microplastics), exposing them to potential harmful impacts. Direct impacts on oyster health and potential movement of impacts up the food chain in the tidal system needs to be investigated further.