The microplastics inundating coastal estuaries and ocean waters around the world can, at high enough levels, kill juvenile oysters.
A recently published study examined how microplastics affect juvenile oysters and found that oysters chronically exposed to microplastics in the lab are likelier to die – which could affect oyster farmers around the world.
The researchers did not specifically test the impact of these microplastic concentrations on seafood consumers, but warned that microplastics could still pose a threat to human health.
"Shellfish containing microplastics consumed whole thus not only pose concern for human or food web exposure, but also for the animals and ecosystem themselves," Thomas Maes, the study’s lead author and principal marine litter scientist at the United Kingdom’s Centre for Environment Fisheries and Aquaculture Research, told SeafoodSource. "If our lab observations indeed occur in the field, microplastics potentially (could) also impact oyster farming, and increasing amounts will only make matters worse."
Oysters are able to remove most particles before ingestion, even as they will ingest some. The effort of filtering out the microplastics can cause exhaustion.
“This continuous augmented filtration without improved food uptake might lead to 'microplastic fatigue.' This exhaustion in combination with non-optimal cell processes probably kills the juvenile oysters," Maes said.
Microplastic exposure did not affect oyster weight or shell length, the study found. Microplastics did, however, affect the stability of the lysomal membrane, which is part of the digestive system and is involved in a variety of cell processes, including defense mechanisms. If the lysomal membrane and lysosomes don’t work properly, the oysters’ long-term health will be undermined, Maes said.
The study tested different concentrations of very small particles of polystyrene that were clean, round, fluorescent microbeads. Microplastics in the environment aren’t nearly so uniform, and often carry dangerous chemicals.
"These results can thus somehow be considered as a 'best case' scenario because in nature we find microplastics to be a mixture of different types, shapes, and sizes contaminated by a blend of chemicals," Maes said.
Researchers don’t often test for such small microplastics in the environment, since they are costly to detect using current methods, instead measuring and testing for larger particles. Even though overall environmental concentrations of such small particles are unknown, it’s likely they exist.
"They are, however, present and the concentrations we used in our study are thus very likely to be representative for environmental conditions in the short and long term," Maes said. "With increasing amounts of microplastics in our environment, it's likely that these lab observations occur in the field, if not already, [then] certainly in the future.”
Photo courtesy of Papakah/Shutterstock
