Marine creatures get a double whammy when they eat tiny bits of plastic that float in the ocean or accumulate in marine sediments. Damage happens when marine organisms eat the plastic, but they also consume toxic pollutants the plastics carry on their surfaces.
Two new studies show that when fish and marine worms eat such a plastic-toxics combo, some of the pollutants accumulate in their bodies and make them sick.
Chelsea M. Rochman at the University of California, Davis, and her colleagues find that fish bioaccumulate flame retardants and other organic pollutants when they eat plastic debris from the ocean, causing hepatic stress (Nat. Sci. Reports 2013, DOI: 10.1038/srep03263).
The team fed microplastic fragments to two groups of Japanese medaka in the laboratory. One group ate polyethylene fragments that had been exposed to the waters of San Diego Bay, thereby sorbing a variety of organic pollutants from the bay, and the other ate virgin polyethylene that had not been in the ocean.
After two months of feeding on the plastics, the bodies of fish that ate ocean-exposed fragments had significantly greater concentrations of total polybrominated diphenyl ether flame retardants, as well as two other persistent organic pollutants. Both groups of fish showed liver stress, but it was far greater in the group that ate the ocean-exposed plastic.
Mark Anthony Browne at UC Santa Barbara and his colleagues found similar results in lugworms, burrowing creatures that eat sediments often contaminated with plastics (Curr. Biol. 2013, DOI: 10.1016/j.cub.2013.10.012). The group fed the worms bits of polyvinyl chloride containing various chemicals, including common additives to plastic and organic pollutants often found on marine microplastics. The chemicals accumulated in worms’ guts at concentrations 326–3,770% greater than that from control sediments. The worms exposed to the chemicals had lower rates of survival and feeding, and impaired immunity.
Both studies show a clear biological response to microplastic pollution, says Hideshige Takada, a geochemist at Tokyo University of Agriculture & Technology. He warns that as the amount of plastics introduced to marine environments increases, the transfer of pollutants to marine life will be “prominent in the near future if we do not take appropriate action.”