The oceans of the world are contaminated with plastics that come from countries around the world. Birds and ocean mammals have been found with large amount of plastic in the their stomachs. Scientists have demonstrated that one reason that birds eat the plastic contained in the world’s oceans is due to its smell. Plastic that has been in the ocean for a long period of time begins to emit a chemical called dimethyl sulfide.
Dimethyl sulfide and the odor that it produces is very similar to the odor that comes from phytoplankton in the ocean. Phytoplankton is one of the main sources of nutrition for animals and fish that live in a the marine environment. When the birds and fish catch the smell of dimethyl sulfide coming off the ocean water soaked plastic, they believe that it is a food source, and they eat it.
Sea turtles have been turning up with large amounts of plastic in their digestive tracks, so marine scientists wanted to experiment and see if the smell of ocean plastic was causing sea turtles to mistake it for food in the same way that birds and some fish do.
Scientists used 15 loggerhead turtles for their experiment. Various scents were placed at the surface of the tanks in which the turtles were housed. The scent of neutral water, shrimp, new plastic and plastic soaked with ocean water were introduced.
When the turtles were introduced to the scent of neutral water and clean plastic, the scientists reported that the turtles had no noticeable changes in their activities. However, when ocean plastic and shrimp scents were introduced, scientists noted that the turtles reacted in much the same way to both scents.
When the turtles smelled shrimp and ocean plastic, the turtles rose to the top of the water and began intense sniffing behavior. This is the behavior of turtles when they are foraging for food items.
As a result of this initial study, scientists are quite sure that sea turtles are ingesting plastic soaked in the ocean because they are mistaking plastic for one of their traditional food sources. This may also help to explain why so many sea turtles are found entangled in plastic. They are investigating a potential food source and then get trapped in a mass of plastic material.
