Plastic in the Ocean

Five trillon pieces weighing almost 269,000 tons. That’s a conservative estimate of how much plastic is our oceans, according to a study published today in PLoS ONE.

The thorough research, conducted by a large team of international scientists, includes data from 24 expeditions collected over a six-year period from 2007–2013 across all five sub-tropical gyres as well as coastal Australia, the Bay of Bengal, and the Mediterranean Sea. The data, accounting for four different sizes of plastic from micro to macro, were collected with nets and visual surveys and then used to calibrate an ocean model of plastic distribution.

The authors were surprised to find that plastic is evenly distributed by latitude, despite the fact that human population (and plastic consumption) is greater in the Northern Hemisphere. In addition, large plastics appear to be abundant near coastlines, degrading into microplastics in the five subtropical gyres. Also unexpected was the presence of the smallest microplastics in more remote regions, such as the subpolar gyres.

The team says that the distribution of the smallest microplastics in remote regions of the ocean suggests that gyres act as ‘shredders’ of large plastic items into microplastics, after which they eject them across the ocean. “Our findings show that the garbage patches in the middle of the five subtropical gyres are not the final resting places for the world’s floating plastic trash. The endgame for microplastic is interactions with entire ocean ecosystems,” says Marcus Eriksen, of the 5 Gyres Institute.

The scientists warn that there is likely much more microplastic in the ocean ecosystem than accounted for in the study, because their estimate does not include “… the potentially massive amount of plastic present on shorelines, on the seabed, suspended in the water column, and within organisms.” And the amount of plastic in the oceans represents only 0.1% of the estimated 288 million tons of plastic produced worldwide in 2012.

Image: Laysan Albatross stomach contents, US Fish and Wildlife