A new study suggests that it’s not only a visual trigger that confuses seabirds to consume toxic marine plastics from the ocean, but smell may play an important part as well. A paper published in Science Advances explains how plastic debris emits a keystone infochemical for olfactory foraging seabirds.
Plastics
Plastic debris is found in every ocean around the world. It has been estimated that there are over five trillion (yep, that’s trillion) pieces of plastic weighing more than a quarter of a million tons floating at sea globally. Most of this plastic debris comes from sources on land and ends up in oceans and bays due largely to poor waste management.
Reducing marine plastic pollution is a long-term, large-scale challenge, but figuring out why some species continue to mistake plastic for food is the first step toward finding ways to protect them. — Matthew Savoca
When it comes to shelf life, plastic has the tenacity of cockroach. It’s non-biodegradable, UV light and wave action just break it into ever smaller pieces. Once consumed by seabirds it can cause a range of problems, from simple starvation due to blockage to poisoning as chemicals leach from the plastic.
Tube-nosed Seabirds
Albatross, Shearwaters, and Petrels all belong to this group and are pelagic meaning they spend the majority of their time at sea searching for food; in many cases for years. During this time they’ll range hundreds of square miles in that search. It’s been assumed that the plastics were visually micking their prey: fish, squid, or krill.
However, tube-nosed seabirds use their powerful sense of smell to hunt. This allows them to be successful even in limited visibility. The authors of this new study, Matthew Savoca, and Gabrielle Nevitt, found that these seabirds clue in on the chemical DMS, or dimethyl sulfide which is produced by algae which in turn are eaten by krill and on up the food chain.
Using a gas chromatograph used to detect sulfur, they found that plastic which had been submerged in the ocean long enough for algae to adhere produced the DMS smell.
Summary
This study suggest that plastic debris may be a more insidious threat to marine life than we previously believed. If plastic looks and smells like food, it is more likely to be mistaken for prey than if it just looks like food.
