We know that plastic pollution continues to build up in the ocean at alarming rates, and we know this poses a risk to the creatures that call it home, but scientists continue to dive into the complex interactions underlying this relationship. The latest study to shed light on this issue paints a startling picture of how the evolutionary habits of juvenile turtles lure them into the most polluted parts of the ocean, demonstrated by the discovery of plastic in the stomachs of young turtles around the coast of Australia.
The research was led by scientists from the UK's University of Exeter, with the team studying a total of 121 sea turtles across five different species collected from the east coast of Australia facing the Pacific Ocean, and the west coast facing the Indian Ocean. These juvenile sea turtles had either washed up onshore or were caught up in the bycatch of fishing operations, and ranged in size from hatchlings to those with shells 50 cm (20 in) across.
Studying the gut contents of these young turtles revealed many had ingested the common plastics polyethylene and polypropylene, presenting as mostly hard fragments in those frequenting the Pacific and mostly fibers in those from the Indian Ocean. The proportion of turtles carrying plastics was much higher in the Pacific, with 86 percent of loggerhead turtles, 83 percent of green turtles and 80 percent of flatback turtles from there containing plastic of some kind.
"These polymers are so widely used in plastic products that it's impossible to pin down the likely sources of the fragments we found," says study author Dr Emily Duncan. "Hatchlings generally contained fragments up to about 5 to 10 mm (0.2 to 0.4 in) in length, and particle sizes went up along with the size of the turtles."
Previous research has shown that organisms like freshly hatched sea turtles have evolved to travel on currents and spend years of their early development in the open ocean. Here, there aren't as many predators to fear and they are free to feed on plankton floating near the surface. But recent research has shown that fluid dynamic processes that drive organisms into these areas also send plastic along for the ride, leaving the turtles to spend key developmental years in what the researchers describe in their study as now some of the most polluted areas of the ocean.
"Juvenile turtles have evolved to develop in the open ocean, where predators are relatively scarce," says Duncan. "However, our results suggest that this evolved behavior now leads them into a 'trap' – bringing them into highly polluted areas such as the Great Pacific Garbage Patch. Juvenile sea turtles generally have no specialized diet – they eat anything, and our study suggests this includes plastic."
Not a lot is known about the way ingested plastic affects marine organisms, and this is a key area of interest for researchers moving forward. Recent studies have, however, begun to shine a light on some of the potential consequences, which could include aneurysms in fish, impaired cognitive performance in hermit crabs, and a weakened physical performance for mussels. Although this is something scientists are yet to explore for young turtles, the fact that they are encountering such high concentrations of plastic so early in life is cause for concern.
"We don't yet know what impact ingesting plastic has on juvenile turtles, but any losses at these early stages of life could have a significant impact on population levels," says Duncan.
The research was published in the journal Frontiers in Marine Science.
Source: University of Exeter