“We’re really at the tip of the iceberg in understanding really where these plastics are winding up,” study coauthor and MBARI researcher Kakani Katija tells The Verge.
Katija and her colleagues performed experiments in which they fed plastic particles smaller than sand grains to the giant larvacean Bathochordaeus stygius, a frequent visitor of Monterey Bay. B. stygius, like other giant larvaceans, constructs massive nests made of mucus, which they use to filter about 11 gallons of sea water per hour. When the MBARI team members fed fluorescent microplastic bits to 25 larvaceans, they found that the majority of the planktonic organisms ingested the particles and pooped them out within 12 hours. They published their findings yesterday (August 16) in Science Advances.
When giant larvaceans excrete microplastics or when they shed their mucus feeding nets, which also trapped the particles, both sink. The authors suspect the waste may be consumed by deep sea-dwelling organisms, providing a route for the pollutants to enter new ecosystems.
“Plastics are sometimes seen as a sea surface issue, and more and more we’re seeing that’s not necessarily true,” Katija tells Science News.
Although the researchers admit that the larvaceans typically swim at depths lower than those at which microplastics float, their findings map a potential route for transfer of the pollutants to new depths. “We are finding pieces of microplastic in deep sea animals and in sea floor sediments,” Anela Choy, Katija’s MBARI colleague and a coauthor on the paper, tells Wired. “We often think of it as just a surface pollution problem, but there are many mechanisms that can transport the [plastic] pollution down from the surface.”