A team of researchers has found that seabirds may be consuming plastic because it smells like their natural food source. Plastic anthropogenic debris releases a type of dimethyl sulfide that mimics the olfactory cues that normally elicit a feeding response in marine birds. The details are in a paper that was just published in the journal Science Advances.
Seabirds, including endangered species, regularly ingest the plastic litter that ends up in the ocean. There has been little research on why this occurs, however. Understanding exactly why seabirds mistakenly eat plastic is critical for eliminating the problem.
Researchers from the University of California studied the sensory mechanisms that may be contributing to the consumption of plastic by seabirds. The team first exposed plastic beads to seawater. The beads were made from the most common types of plastic litter– poly-propylene, high-density polyethylene, and low-density polyethylene. The beads were placed in small mesh bags and left in the ocean off the Californian coast. After three weeks, the researchers collected the beads to analyze their chemical signatures in an attempt to learn what the beads may smell like to birds.
The research team found that the plastic beads were emitting dimethyl sulfide (DMS). DMS is an odorant that seabirds associate with food. When zooplankton (the main source of food for many marine birds) consume phytoplankton, DMS is released. The scent elicits a feeding response from seabirds, especially species that heavily rely on their sense of smell to find food. When plastic sits in the water, it absorbs the DMS, making the plastic smell appetizing to the birds.
The team’s findings provide an explanation for seabirds’ attraction to marine plastics. The litter begins to smell like food and the birds mistakenly consume it. Species that primarily use DMS scents to find food, such as the albatross, are especially vulnerable to this form of pollution. The authors hope that their study will help scientists develop solutions to the problem of plastic consumption by wildlife.
Savoca et al. Marine plastic debris emits a keystone infochemical for olfactory foraging seabirds. Science Advances (2016).