Researchers led by Matthew Savoca from the University of California, Davis in the U.S. found microplastics in seawater emit a chemical irresistible to seabirds because it's the same as a compound that signals that prey is nearby.
Savoca said their findings do not refute that plastic might also look like food to other marine animals that eat it, but it does affirm that when plastic looks and smells like food, it becomes more appealing to seabirds.
But the new research finds the birds may be homing in on plastic trash, which gets coated with organic matter and ends up giving off a dying-algae smell.
Birds derive no energy from consuming plastic, unlike, say, actual food, so the animals are expending both time and energy attempting to consume and digest it, and filling their bellies with wasted content.
'Yet, based on their foraging strategy, this study shows they're actually consuming a lot of plastic and are particularly vulnerable to marine debris'. Species of bird that are known to respond to DMS signals were shown to consume plastic five times as frequently as non-DMS-responsive species.
The chemical really stinks up the place, and that is irresistible for seabirds such as shearwaters, which can not tell apart algae from plastic that smells just the same.
Unlike humans, seabirds such as shearwaters, petrels, and albatrosses can easily pick up this scent, which they immediately associate with food.
Plastic pollution in the sea gives off a smell that attracts foraging birds, scientists have found. The beads were made from the most common types of plastic litter- poly-propylene, high-density polyethylene, and low-density polyethylene.
To identify the chemical behind the smell, the scientists took the soggy plastic to UC Davis's Department of Viticulture and Enology.
Tube-nosed seabirds such as petrels and albatross, who have a keen sense of smell that they use to hunt, are attracted to this odor - which, as the researchers put it, is the birds' version of a "dinner bell". They may suffer from malnutrition, intestinal blockage, or slow poisoning from chemicals in or attached to the plastic. Now, the new study claims to have discovered the chemical clue to why these creatures eat plastic. There we used a gas chromatograph, specifically built to detect sulfur odors in wine, beer and other food products, to measure the chemical signature of our experimental marine debris. They also happen to be severely affected by plastic consumption.
DMS also results when plankton, which collects on waste plastic objects, breaks down.
To see if the odor of plastic ocean debris was confusing seabirds, Savoca and his colleagues deployed plastic beads in mesh bags at two locations off the California coast. Their best guess was it looks like food, but now there's evidence that for a lot of birds, plastic actually smells like food. This difference matters because populations of hard-to-observe burrow-nesting seabirds are more difficult to count than surface-nesting species, so they often are not surveyed as closely. The team first exposed plastic beads to seawater.