Tracking tiny bits of plastic
UK scientist details marine pollution impact on food web
The evidence of our throwaway society spreads from coastal beaches and waterways to the North Pacific Ocean garbage patch and down to the sediment of the world’s ocean floors.
“Plastic pollution is such an ubiquitous problem, we don’t see it or consider it as pollution,” observed ecotoxicology Professor Tamara Galloway, speaking to Ocean State scientists gathered April 12 for the Rhode Island NSF EPSCoR 2017 Annual Research Symposium. “Why is that? What do we need to know to take plastic pollution seriously or do we even need to take it seriously?”
The University of Exeter, UK, researcher launched her guest talk at the event, co-hosted by Brown University and Rhode Island School of Design, with these questions and recounted an effort with colleagues and volunteers to gauge the scope of the problem at a local beach. The group collected all visible plastic on a 25-meter stretch of Tregantle Beach, which sits on the western end of South East Cornwall’s Whitsand Bay.
On that one piece of beach, on one day in July 2014, Galloway said, the group collected 567,664 plastic items: “If you put numbers to the problem, then you can start to take it seriously.”
About 10 percent of all discarded plastic reaches the sea, totalling 10 million tons, with a shelf life of hundreds of years, noted Galloway, and causing the death or maiming of one million seabirds and 100,000 marine mammals each year. The record amount ingested by one bird stands at 84 pieces, according to the National Oceanic and Atmospheric Administration (NOAA).
Tinier bits of plastic measuring less than five millimeters in diameter, float by unseen, but Galloway and others are studying just how lethal they may be.
Gut reaction: The microplastic journey
“Why we’re worried about microplastics is that they start to overlap with the size of prey,” Galloway noted. “Many marine animals — filter feeders — at the base of the food web are ingesting pieces of plastic and passing it up the food web.”
This data suggests that plastic ingested by bivalves destined for the dinner plate means the typical human eating an average 100 grams of shellfish will consume 50 tiny pieces of plastic. For the regular consumer, that equals about 11,000 pieces in the course of a year. Galloway also studied what happened when crabs were fed mussels that had ingested microplastics to better understand the trophic transfer.
“We were expecting to see that the plastic might end up in the crab, but the plastic ended up staying in the gut of the crab up to 14 days later,” she said. “Plastics were in the gut and still being excreted.”
This led to the question of why the plastic remained in the gut for such a long period of time. Galloway said the research found that the plastic became embedded in the crab’s foregut setae and adhered to its gill lamellae as well. Other research investigated what happens from sediment to surface, looking at species like the common blood worm, living on the ocean floor, and plankton, floating in the water column. Even tiny oyster larvae ingest plastic nanoparticles — the smaller the better — until 28 days old, when they turn to larger pieces.
“There is evidence from a range of different species that plastic is being ingested and stays (in the body) for a long period of time,” she said, raising serious follow-up questions.
Do plastics alter faecal pellets, making them more buoyant? Does that lead to altered carbon cycling? Do microplastics sink? Is there enough plastic in the ocean to make a difference? To help resolve these and other issues, Galloway said researchers were working to identify whether contamination hotspots existed, using particle tracking models to determine how currents might move a piece of plastic dropped in the water.
Future work will look at the food chain, Galloway added: “Is there any consequence for us? Do we want to be eating seafood with plastic in it?”
Shifting from the dire outlook, Galloway said she wanted to end her talk on a more hopeful note. She pointed to oil spills as an example, comparing how they were handled in the 1970s to now with increased awareness, attention and vigilance.
“If there is concerted action, policy change is possible,” said Galloway. “And hopefully, this kind of science can help.”
2017 Annual Research Symposium: A showcase of Ocean State research, facilities
The daily catch: Marine debris & beach trash in Rhode Island
Arctic Ocean accumulation: A dead end for floating plastic
In addition to Galloway’s afternoon talk, the daylong event showcased a poster presentation of RI EPSCoR- related research and tours of RI EPSCoR-supported and core facilities — the Nature Lab at RISD, and the Center for Computation and Visualization (CCV) and NSF/EPSCoR Shared Proteomics Facility at Brown.
Members of Rhode Island’s congressional delegation — Sen. Jack Reed, Rep. Jim Langevin and Rep. David Cicilline — joined a luncheon at Brown University’s Alumnae Hall and shared welcoming remarks. The legislators highlighted the importance of scientific research both statewide and nationally, and said they would continue to lend their vigorous support to the discovery process. Unable to attend, Sen. Sheldon Whitehouse was represented by Director of Community Affairs Aida Crosson.
Story by Amy Dunkle|Photos by Michael Salerno