"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."
As test subjects, lugworms were not chosen at random. They are found in the United States and Europe, where they comprise up to 32 percent of the mass of organisms living on some shores, and are consumed by birds and fish and used as bait by fishermen. When the worms feed, they strip the sediment of silt and organic matter, giving rise to a unique and diverse number of species. Consequently, governments use this species to test the safety of chemicals that are discharged in marine habitats.
"They also suffer from mass mortalities during the summer," Browne said of the worms. "In the areas where a lot of the mortalities occurred, there has been extensive urban development so some mass mortalities could be potentially tied to plastic. On a hot summer's day when the tide is out, these organisms cook slightly because their hydrogen peroxide levels increase. And we found that the plastic itself reduces the capacity of antioxidants to mop up the hydrogen peroxide."
Although sand transferred larger concentrations of pollutants up to 250 percent into the worm's tissues, pollutants and additives from microplastic accumulated in the gut at concentrations between 326 percent and 3,770 percent greater than those in experimental sediments.
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, h
|Contact: Julie Cohen|
University of California - Santa Barbara