"Plastic Debris in the World's Oceans" said at least 267 species -- including seabirds, turtles, seals, sea lions, whales and fish -- are known to have suffered from entanglement or ingestion of marine debris.

    Some 80 percent of this debris comes from land and 20 percent from the oceans, the report said, with four main sources: tourism, sewage, fishing and waste from ships and boats.

    "It's not necessarily an area that's clearly defined; it's sort of a natural phenomenon ... wind and salt water break down the plastic," said Steve Smith, aboard the Greenpeace ship Esperanza.

    "We've been unfortunately finding a lot of stuff out here, floating by, which doesn't paint a very good picture, because some of it is from faraway places, has marine life like barnacles and other little creatures living on the plastic," Smith continued.

    Ocean currents and tides carry the plastic, which takes a long time to biodegrade, thousands of miles to an area near the Northwestern Hawaiian Islands that was designated a protected U.S. national monument by President George W. Bush in June.

    It's there that marine life eats it, gets tangled in it, and dies.

    By hitching rides on plastic debris, invasive species can be carried thousands of miles to interact with native creatures. Plastic also poses a hazard to animals that mistake it for prey and eat it,. Smith said.

    "Plastics in the oceans act as a toxic sponge, soaking up a lot of the persistent pollutants out here," Smith said. "We've seen photos of albatrosses who eat this plastic ... Even though their stomachs are filled, they end up starving because there's no nutrients in there."

    The new report comes days after the journal Science projected that Earth's stocks of fish and seafood would collapse by 2048 if trends in overfishing and pollution continue.

    And two weeks ago, the U.S. Institute of Medicine said the benefits of eating fish outweigh the risks of toxins detected in the animals.

    The report said an international agreement known as MARPOL is aimed at ending the dumping of plastic debris at sea, but noted that since most debris originates on land, even total enforcement of this agreement would not eliminate the problem.

    Greenpeace called for a global network of marine reserves, covering 40 percent of the world's oceans, and responsibility by coastal countries to cut down on "excessive consumption" and boost recycling.

    (Agencies)