SOURCE: National Geographic/Laura Parker – November 9, 2016
A new study sheds light on why so many seabirds, fish, whales, and other critters are gobbling up so much marine plastic debris. And it’s not quite what scientists thought.
As the oceans fill with plastic debris, hundreds of marine species eat astonishing amounts of it. Yet the question of why so many species, from the tiniest zooplankton to whales, mistake so much of it for food has never been fully explored.
Now a new study explains why: It smells like food.
Algae are consumed by krill, a small crustacean that is the primary food source for many sea birds. As algae breaks down naturally in the ocean, they emit a stinky sulfur odor known as dimethyl sulfide (DMS). Sea birds in the hunt for krill have learned that the sulfur odor will lead them to their feeding grounds.
It turns out that floating plastic debris provides the perfect platform on which algae thrives. As the algae breaks down, emitting the DMS odor, sea birds, following their noses in search of krill, are led into an “olfactory trap,” according to a new study published November 9 in Science Advances. Instead of feeding on krill, they feed on plastic.
“DMS is the dinner bell,” says Matthew Savoca, a doctoral student at the University of California, Davis, and lead author of the study. “When people hear the dinner bell, we know food is going to be in the area. This is the same sort of idea. Once the birds’ noses have told them this is where they should expect to find krill, it gets their foraging mode turned on, and their threshold is down for what the food is. ”
Plastic debris has been accumulating rapidly in the world’s ocean, roughly doubling every decade. In 2014, a global analysis measured ocean plastic at a quarter of a billion metric tons, much of it suspended in small rice-sized particles. More than 200 animal species have been documented consuming plastic, including turtles, whales, seal, birds, and fish. Seabirds are especially at risk; a study published last year by scientists in Australia concluded that virtually all seabirds have consumed plastic.