Humans produce hundreds of millions of tons of plastic every year, in the process littering the globe with all the non-biodegradable debris. Plastic fragments ride wind gusts and ocean currents to remote regions of the world that might otherwise remain untouched by humans. In the last issue of Pacific Standard, Brooke Jarvis documented the unforeseen consequences of plastic pollution on Midway Island, where well-meaning Laysan Albatross parents feed plastic fragments to their nestlings; too weak to fledge, the young birds often starve to death on the island. But the albatross is hardly the only animal suffering as a result of widespread plastic pollution.
An international team led by researchers at the University of Exeter set out to define our state of knowledge on the impact of plastics on marine turtles. Their review, published today in the ICES Journal of Marine Science, shows that, while studies on the subject are somewhat scarce, the existing research finds cause for concern. According to the review, every species of marine turtle has been observed to consume plastic fragments. As visual hunters, sea turtles are at high risk of mistaking plastics for prey—confusing a buoyant plastic bag for a swimming jellyfish, for example.
Every species of marine turtle has been observed to consume plastic fragments.
Juvenile sea turtles may be most at risk. Plastic on beaches can alter the temperatures of the sand where turtle eggs incubate, skewing the sex ratios of nestlings. (For sea turtles, sex is temperature dependent.) The authors themselves have even observed large plastic debris trapping hatchlings in the nest. When those babies do make it out of the nest, strong ocean currents drag hatchlings to foraging hotspots. But those same forces pull in debris as well, increasing plastic exposure for the young animals, whose small size makes ingesting plastic all the more dangerous. Even if the plastic doesn't kill the animals by blocking or rupturing their digestive tracts, all those buoyant objects in the turtles' intestines could impede their ability to swim and dive. The sub-lethal effects of consuming plastics—which accumulate toxins and heavy metals that can leech out into the turtles' tissues as the plastic slowly breaks down in their guts—are largely unexplored, the team finds.
The majority of existing research, the researchers found, focused on green and loggerhead turtles, and tends to be concentrated in the Atlantic, leaving substantial gaps in knowledge. This team thus calls on researchers to carry out more studies of plastic exposure in all seven species of marine sea turtles across all life stages and a wider geographical region.
Quick Studies is an award-winning series that sheds light on new research and discoveries that change the way we look at the world.