Lead author Mark Anthony Browne, a postdoctoral fellow at NCEAS, had two objectives when the study commenced: to look at whether chemicals from microplastic move into the tissues of organisms; and to determine any impacts on the health and the functions that sustain biodiversity.
Microplastics are micrometer-size pieces that have eroded from larger plastic fragments, from fibres from washing clothing or from granules of plastic added to cleaning products. They are then consumed by a variety of animals, beginning with the bottom of the food chain. These tiny bits of plastic act like magnets, attracting pollutants out of the environment to attach to the plastic.
The study showed that large accumulations of microplastic have the potential to impact the structure and functioning of marine ecosystems.
Browne ran laboratory experiments with colleagues in the United Kingdom in which they exposed lugworms (Arenicola marina) to sand with 5 percent microplastic (polyvinylchloride) that also contained common chemical pollutants (nonylphenol, phenanthrene) and additives (triclosan, PBDE-47).
Results showed that pollutants and additives from ingested microplastic were present in the worms' tissues at concentrations that compromise key functions that normally sustain health and biodiversity.
"In our study, additives, such as triclosan (an antimicrobial), that are incorporated into plastics during manufacture caused mortality and diminished the ability of the lugworms to engineer sediments," Browne said. "Pollutants on microplastics also increased the vulnerability of lugworms to pathogens while the plastic itself caused oxidative stress."
The pollutant nonylphenol from microplastic or sand suppressed immune function by more than 60 percent. Triclosan from microplastic diminished the ability of worms to engineer sediments and caused mortality, each by more than 55 percent.
Triclosan, an antibacterial additive, has been found in animal studies to alter hormone regulation. Microplastic also increased the worms' susceptibility to oxidative stress by more than 30 percent.
The study was published in journal Current Biology.