Space & Innovation

Coastal Barriers Could Catch 1/3 of Ocean Plastic

Catching plastic pollution at the source is best, researchers argue. Continue reading →

In December, in what's been touted as the most comprehensive analysis so far of plastic pollution in the world's oceans, researchers estimated that there are now as many as 51 trillion particles of floating plastic, which cumulatively weigh up to 236,000 metric tons. That's a whole lot of plastic, and it's having a catastrophic effect upon aquatic animals such as sea birds. Another recent study reports the birds often have bellies full of plastic waste.

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But how do we stop all that plastic - much of which is discarded by fast-developing Asian countries - from floating out to sea and disrupting ecosystems? Some see better waste-handling methods as the answer, while the the Ocean Cleanup Project advocates deploying barriers to contain plastic around the Great Pacific Garbage Patch, the vast gyre where much of the plastic and other trash have gathered, to limit and contain the mess while it's being cleaned up.

But Imperial College London oceanographer and climate scientist Erik van Sebille is advocating an even more radical solution. He advocates putting the plastic-collecting barriers off the coast of China and Indonesia, two major contributors to the world's plastic pollution problem. In a new study published in Environmental Research Letters, he and co-author Peter Sherman conclude that such a movie would eliminate nearly a third of the tiny pieces of microplastic that are entering the oceans.

"It makes sense to remove plastics where they first enter the ocean around dense coastal economic and population centres," van Sebille said in an Imperial College press release. "It also means you can remove the plastics before they have had a chance to do any harm. Plastics in the patch have traveled a long way and potentially already done a lot of harm."

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In the study, van Sebille and Sherman used both surface and satellite-tracked buoy observations to simulate floating microplastic waste over the next decade. They assessed the sources of plastic and calculated the best places to focus on containing and cleaning up the pollution.

They found that placing plastic collectors like those proposed by The Ocean Cleanup project around coasts was more beneficial than placing them all inside the patch. The project proposes a system of floating barriers and platforms to concentrate and collect plastics and remove them. For a ten-year project between 2015 and 2025, the team found that placing collectors near coasts, particularly around China and the Indonesian islands, would remove 31 per cent of microplastics. With all the collectors in the patch, only 17 per cent would be removed.

Here is a sample of the plastic waste collected from a Pacific atoll.

Out To Sea

Our oceans have a pollution problem. Over a decade ago, the North Pacific Gyre was discovered harboring untold tons of plastic trash, and quickly became known as the "Great Pacific Garbage Patch." It was a shocking wake-up call to the world which showed that even the most remote corners of the global were not immune to our throw-away culture. There are five main gyres in Earth's oceans. In January, members of the ocean advocacy group 5 Gyres set out to chart the North Atlantic Gyre. They're suspicion: that the world's water was more polluted than anyone knew, and that a "Great Atlantic Garbage Patch" was lurking somewhere between the U.S. Virgin Islands and Bermuda. But no one had ever looked for it before.

First Trawl

No sooner had the first trawling net been raised from the water than the crew's worst fears were confirmed: plastic. The material's pervasiveness struck Stiv Wilson who, as he says, "began the cruise an independent journalist, and ended it a board member of 5 Gyres." "If you look for it, you will find plastic everywhere, in or out of the gyres," Wilson said. "If you go two miles off the coast of San Francisco and trawl you will find it. It's denser in the gyres, but it's everywhere."

Sampling by Hand

Most of the brown gunk in this image is natural. It's sargassum algae, which gives the North Atlantic Gyre its other name: Sargasso Sea. But the white flecks researchers are reaching for are chunks of plastic floating near the surface. Contrary to what many people think, ocean "garbage patches" are really more like thin stews of pollution. All shapes and sizes of plastic trash hang in the water column, sometimes very spread out, sometimes arranged by wind patterns into dense lines that extend to the horizon.

The Big Stuff

During nearly 40 trawls of the North Atlantic Gyre taken throughout the trip, the net never came up empty. "We got plastic every single time," Wilson said. This pile of garbage was hauled out of the water by hand over the course of about 40 minutes. "This was just two people using crappy pool nets to scoop stuff up," Wilson said. "We got 10 percent of all the stuff in the water, maybe."

The Little Stuff

In amongst small-fry lanternfish are blue flecks of plastic, and even a few BB-sized pellets of "nurdles" -- bits of virgin plastic that fell off a freighter or were washed down a river and into the ocean before they were ever made into a product. "As I like to say, 'shit rolls downhill, and at the very bottom of the hill are the oceans,'" Wilson said. Major rivers like the Columbia and the Mississippi can carry huge amounts of plastics into the oceans, where they remain permanently. Once in the open ocean, plastic may be mistaken for food by fish like the lanternfish. Scientists don't know how often this happens, but they worry that chemicals trapped in plastic could leach into animal tissues and begin a slow march up the food web. Sea birds, large ocean predators -- even people -- may be having this stuff for lunch without even knowing it.

Plastic Reef

Along for the ride was Dutch artist Maarten vanden Eynde (left), who is collecting material to build a reef 40 meters long by 10 meters wide (131 x 33 feet) out of plastic removed from the ocean. He was not disappointed. The expedition collected 876 pounds of plastic, some of it from beaches in the Virgin Islands and Bermuda, but mostly from the open ocean. That included what Stiv Wilson called "his favorite piece of plastic" (right) -- a small fleck with the word "from" still visible, looking like a fractured message from whoever discarded it.

A Losing Battle?

Hauling plastic out of the oceans by hand is never going to work. Wilson said that for the time it takes to fill a freighter with junk, several times that much will be dumped into the sea through everyday human activity. "It's growing at an alarming rate," he said, though he admitted that no one's really sure how much plastic is dumped every year, or how much makes its way to the gyres.

What's Next?

Like the name says, the goal of 5 Gyres is to explore all five of Earth's main ocean gyres. So far the North Atlantic and Pacific gyres are the only ones to have been extensively surveyed. But Wilson said that his colleagues have found plastic in the Indian Ocean gyre during a recent preliminary cruise. "The problem is growing at an alarming rate," he said. The only way to stop it is a dramatic reduction of the plastic we use today, especially single-use items like coffe cup lids, grogery bags, and soda straws. "You're not seeing car bumpers out there," Wilson said. "It sounds trite, but really what's needed is a grassroots effort to reduce our addiction to single-use plastics."