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The great Pacific garbage patch may be 16 times as massive as we thought

New estimates put greater weight on larger plastics

By
10:00am, March 22, 2018
fishing net washed ashore

THINGAMABOBS  Fishing nets and ropes make up 47 percent of the plastic mass in the Pacific Ocean’s notorious garbage patch, a new study suggests.

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A pooling of plastic waste floating in the ocean between California and Hawaii contains at least 79,000 tons of material spread over 1.6 million square kilometers, researchers report March 22 in Scientific Reports. That’s the equivalent to the mass of more than 6,500 school buses. Known as the great Pacific garbage patch, the hoard is four to 16 times as heavy as past estimates.

About 1.8 trillion plastic pieces make up the garbage patch, the scientists estimate. Particles smaller than half a centimeter, called microplastics, account for 94 percent of the pieces, but only 8 percent of the overall mass. In contrast, large (5 to 50 centimeters) and extra-large (bigger than 50 centimeters) pieces made up 25 percent and 53 percent of the estimated patch mass.

Much of the plastic in the patch comes from humans’ ocean activities, such as fishing and shipping, the researchers found. Almost half of the total mass, for example, is from discarded fishing nets. A lot of that litter contains especially durable plastics, such as polyethylene and polypropylene, which are designed to survive in marine environments.

Piling up

Researchers sorted plastic particles by size and type, including pieces of hard plastics and thin sheets, nets and ropes and other forms like foam. Based on new estimates, the plastic mass mostly comes from very large particles bigger than 50 centimeters. The bulk of those particles are fishing nets and ropes.

An inventory of plastic in the great Pacific garbage patch

To get the new size and mass estimates, Laurent Lebreton of the Ocean Cleanup, a nonprofit foundation in Delft, the Netherlands, and his colleagues trawled samples from the ocean surface, took aerial images and simulated particle pathways based on plastic sources and ocean circulation.

Aerial images provided more accurate tallies and measurements of the larger plastic pieces, the researchers write. That could account for the increase in mass over past estimates, which relied on trawling data and images taken from boats, in addition to computer simulations. Another possible explanation: The patch grew — perhaps driven by an influx of debris from the 2011 tsunami that hit Japan and washed trash out to sea (SN: 10/28/17, p. 32).

Citations

L. Lebreton et al. Evidence that the Great Pacific Garbage Patch is rapidly accumulating plastic. Scientific Reports. Published online March 22, 2018. doi: 10.1038/s41598-018-22939-w.

Further Reading

M. Quintanilla. Here’s a breakdown of the animals that crossed the Pacific on 2011 tsunami debris. Science News. Vol. 192, October 28, 2017, p. 32.

C. Samoray. Ocean’s plastics offer a floating fortress to a mess of microbes. Science News. Vol. 189, February 20, 2016, p. 20.

J. Rosen. Trash researcher tallies ocean pollution. Science News. Vol. 187, January 24, 2015, p. 4.

B. Mole. Plastic may take unexpected routes to marine garbage patches. Science News. Vol. 186, October 4, 2014, p. 13.

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