Tons of plastic waste washes into oceans every day. Sometimes, the same plastic is found in the stomachs of dead marine creatures. Recently, scientists have found out that it is not a coincidence. These fishes, birds and animals do not ingest plastic by accident, instead, they actually think plastic is food.
Plastic that has been in the ocean for a while emits a chemical that smells a lot like food to some seabirds and fishes. This chemical is the dimethyl sulfide gas, which is also produced by phytoplankton, a key food source for many marine animals. Loggerhead sea turtles (Caretta caretta) also may confuse the smell of plastic with food, according to a study published March 9 in Current Biology.
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. It was seen that turtles ignore 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.