Plastic ocean debris poses potential harm to marine turtles

BRISBANE, AUSTRALIA — Marine turtles, like seabirds, are ingesting a significant amount of plastic debris, a new research report has found.

Australian scientist Qamar Schuyler has just completed a report that found 52 percent of marine turtles worldwide are likely to have eaten plastic debris.

Schuyler is a research fellow at the University of Queensland's Moreton Bay Research Station, on Moreton Island off the south Queensland coast.

Her study, conducted as part of her doctor of philosophy thesis, analyzed data from previously published research and debris modeling to conclude that the riskiest locations for turtles are the east coasts of Australia and North America, Southeast Asia, Southern Africa and Hawaii. Those sites have high species diversity and more marine debris.

Schuyler told Plastics News her research included necropsies she conducted of 100 dead turtles found on the southern Queensland coastline and data provided by other marine biologists from necropsies on about 90 animals, mainly caught in long-line fishing operations in the North Pacific Ocean.

Her research follows publication of a similar study on seabirds, which found 60 percent of the world's seabirds have plastic fragments in their stomachs. It predicts the figure will increase to 99 percent by 2050.

Schuyler said turtles can pass some plastic fragments, but most remain in their bodies. Ingested plastic can kill turtles by blocking the gut or piercing the stomach wall and can release toxic chemicals into the animals' tissues.

“Very little — just 0.5 grams — is enough to kill a turtle,” she said.

The products ingested vary according to turtles' ages. Young turtles, which head out to sea to escape predators after they hatch, are more likely to eat “small, hard plastic [fragments], mainly white.” Schuyler said that is probably because fragments are predominant in debris in the oceans. “Baby turtles eat non-specifically, they chow down on anything out in the ocean,” she said.

They are “filling their bellies” with plastic fragments that float in the oceans.

More mature turtles feed more specifically on the ocean floor, so are more likely to ingest film, which they mistake for jellyfish.

“Their dominant preference is soft, clear plastics. They are generally larger pieces, so more likely to cause harm,” Schuyler said.

Older turtles, though, are “less naive,” and have “some capacity” to know the difference between plastics and real food. They have less contact with floating debris because they feed on the ocean floor.

Schuyler said the researchers' biggest focus for waste reduction is on single-use plastics, like shrink wrap used around pallets, disposable cutlery, and plastic packaging.

“Behavior changes and viable alternatives are needed,” she said.

Schuyler was part of an Australian government-organized focus group that brought together scientists, environmentalists and resin producers. She said the two-day “brainstorming session” developed “sheets of solutions” that are now being examined to see which are feasible.

She said resin pellet manufacturers seem “happy to come on board,” but it is “harder at the next level, the converters.” A whole-of-life mentality is not built-in when considering the lifecycle of products they manufactured

Schuyler's research examined debris ingestion by six species. The most at-risk is the Olive Ridley turtle, found in warmer waters of the southern Atlantic, Pacific and Indian oceans. “They are the most likely to ingest, because they feed in the mid-water column and target jellyfish,” she said.

The leatherback turtle is renowned for ingesting plastic bags, because it eats only jellyfish.

Schuyler said it is “very difficult” to know how much plastic debris enters the oceans, with researchers' estimates ranging from four tons to 12 tons a year.

Schulyer's research study has been published in Global Change Biology, a scientific journal.