You've heard about those huge floating garbage patches out in the middle of the ocean? Well, now researchers think there's a whole lot more plastic out there than anyone thought. Most of it is just hidden from view.

In Marvin Gaye Park in Washington, D.C., there's a trash trap over the creek that skims the surface for floating trash. There's a plastic water bottle, an ice cream container, a potato chip bag, a beer can. All in all, the trap catches about 800 pounds of trash a month.

But over almost all the other streams in the area, there are no trash traps. In most streams, trash like this will float into the river and out into the ocean. And then a tiny bit of it might end up in the plastic archive collection, at the Sea Education Association in Woods Hole, Massachusetts.

Mary Engels, SEA's science coordinator, pulls out a little shoe polish-like tin and points to the dozens of tiny pieces of plastic inside.

"These samples were taken in the Sargasso sea to the east of Bermuda," Engels says.

The Sargasso Sea is about a thousand miles out in the Atlantic, part of what's called a subtropical gyre—a giant swirl of calm water near the equator. The earth has five big ones, each thousands of miles across. The way the planet spins and the currents flow, the gyres end up collecting all kinds of trash.

SEA researchers skimmed the surface of the North Atlantic gyre with a meter-wide net for about a mile. They came up with blue, green, and white plastic specks, pieces of opaque sheet plastic, even plastic fibers.

Plastic specks were once fishing gear, clothing, plastic bags, and Styrofoam.

It's hard to tell by looking at the bits what they once were or where they came from, but Giora Proskurowski, a research scientist at the University of Washington who's worked with SEA, has a pretty good idea. There's a lot of polypropylene, Proskurowski says, "which is a lot of fishing gear, lines, nets. Clothing is often polypropylene, yogurt containers. Polyethylene, which are your plastic bags. And the last is your Styrofoam."

As for where it came from? Proskurowski says in the North Atlantic, "it's almost certain that the sources of plastic are the United States, Europe, the Gulf and Caribbean region."

Each one of the five big oceanic gyres sucks in trash from the countries along the surrounding coast. Scientists have known about these giant swirls of trash for years, but Proskurowski says there is probably much more of it than anyone ever thought, because most of it is usually swirling below the surface.

Proskurowski's "aha" moment came when he was in the middle of the North Pacific gyre.

"The surface of the ocean was flat calm, (and) all of a sudden I saw hundreds of thousands of little tiny pieces of white and blue plastic. It was like when a photograph comes into focus perfectly, and everything just pops out. And as soon as the wind started kicking up, within a half an hour you could no longer see those plastic pieces."

Proskurowski went on to research this, and found that the wind was pushing the garbage down in the water column.

"After that we started doing subsurface tows, where we towed three meters below the surface, five meters below the surface, and on every one of those tows I caught plastic," he says.

North Pacific Trash up "100 times"

There is conflicting research from different oceans, but one recent survey by researchers at the Scripps Institution of Oceanography in San Diego found that the amount of plastic in the North Pacific has increased by 100 times over the last four decades.

But despite the huge influx, Scripps graduate student Miriam Goldstein says there is no "island" of trash.

"There's this misconception that there's a big floating garbage dump you can see and walk on. But actually, most of the plastic is really small."

So what then is the big deal?

Goldstein says when it comes to plastic trash in the oceanic gyres, small is probably worse than big, "because if there was an island, it'd be easy to fix—send a barge out there, pick it up, done."

The problem is that marine animals and sea birds eat this plastic. SEA's Karen Lavender Law, who's collaborated with Giora Proskurowski, has seen it first hand.

"We brought aboard this beautiful fish," Law says, "and in the name of science we dissected it, and in the name of dinner we filleted it, and in the gut there was some piece of plastic, gridded material two by three inches in size."

It's worrisome because plastics can gum up an animal's systems. Law says they also act like sponges for more harmful persistent pollutants like PCB's, which they then transfer to animal's fatty tissue. And the plastics themselves can break down into harmful chemicals.

There's little data on exactly what all this plastic is doing to ocean going life. But researcher Giora Proskurowski says "the fact that there's any plastic there at all is what's important. When you're 2,000 miles away from land and can dip your net in the water and get 200 pieces of plastic, that seems insane to me. It's like going to the very farthest part of the Amazon and seeing plastic bags in every single tree."

Proskurowski says it's something to think about next time you buy something in a plastic bag or toss out a plastic bottle.

From PRI's The World ©2015 Public Radio International