More than 5 trillion pieces of plastic are afloat in the world’s oceans, according to a new study published Wednesday in the journal PLOS One.
Ranging in size from a grain of salt to larger than a plastic water bottle, the plastic pollution in the world’s oceans weighs more than 269,000 tons—far more than all the gold ever mined in the world and far more than scientists previously estimated.
Study author Marcus Eriksen and his team from the 5 Gyres Institute, based in Los Angeles, spent tens of thousands of hours scouring the world’s oceans for plastic between 2007 and 2012. They used trawling nets to scoop particles from the ocean surface and visually counted very large pieces. The study provides a snapshot of the magnitude of marine plastic pollution and its movement around the world’s oceans, said Eriksen.
The estimate is much higher than what previous studies found.
Marine ecologist Andrés Cózar, who teaches at the University of Cádiz in Spain, calculated that as much as 40,000 tons of plastic was dispersed in the surface waters of the open ocean. Cózar and his colleagues found that only 1 percent of the plastics they netted from the oceans were larger than 10 centimeters.
“If you separate out the larger pieces, we’re in the same ballpark,” said Eriksen, whose study included larger-sized plastic.
Eriksen’s team also ventured into regional seas—the Mediterranean, the Bay of Bengal, and the ocean off Australia—that had not been included in other analyses.
“They have data in places where we had very few or no data,” said Kara Lavender Law, a physical oceanographer at the Sea Education Association who studies ocean circulation and the distribution of plastic marine debris.
The current study found that large plastics accounted for more than 75 percent of the ocean haul—an unexpected result. Because most microplastics come from the breakdown of larger plastic items, the team expected the smallest microplastics to be the most abundant. “Smaller plastics are removed from the surface very quickly,” said Eriksen. “The smaller it gets, the faster it leaves the surface.”
“It’s evidence that there is too much plastic in the ocean,” Cózar said in an email. “Only two or three generations have been using plastic materials. This provides evidence that the current model of managing plastic materials is economically and ecologically unsustainable.”
Eriksen’s team fed the plastics information into a computer model of the world’s ocean currents that assumes that plastics enter the oceans from rivers, storm and sewer drains, shipping lanes, and densely populated coastlines. The model found that the largest plastics are abundant around coastlines and then move to the subtropical gyres, where they degrade into micro plastics. These micro plastics then it seems get into the food chain as the are inadvertently consumed by sea life