To a sea turtle, plastic debris might
smell like dinner.
As the plastic detritus of
modern human life washes into oceans, marine
creatures of all kinds interact with and sometimes eat it (SN: 11/13/19). Recent research suggests that
this is no accident. Plastic that’s been stewing in the ocean emits a chemical
that, to some seabirds and fish, smells a
lot like food (SN: 11/9/16). That chemical gas, dimethyl sulfide,
is also produced by phytoplankton, a key food source for many marine animals.
Over two weeks in January 2019, 15 captive
loggerheads in tanks were exposed at the water surface to a slew of scents,
including the largely neutral scent of water as a control, of food such as
shrimp and of new and ocean-soaked plastic.
The turtles (Caretta caretta) largely ignored smells of water and clean plastic.
But when the scientists puffed air containing scents of either food or ocean-stewed
plastic, the reptiles increased their sniffing above water — a typical foraging
behavior. In fact, those responses to food and ocean-soaked plastic were indistinguishable
to the researchers, suggesting that the plastic can induce
foraging behavior in sea turtles, the team says. That might explain
why sea turtles get entangled in or eat plastic, which can be harmful.
Along with previous research, this study expands the breadth of marine life that may confuse plastic with food.