Photo: A sea cucumber in a Dubai aquarium. Credit: Maxim Gavrilyuk via Wikimedia Commons

Humans discard somewhere between 4.8 and 12.7 million tons of plastic waste in the world's oceans each year. That staggering amount of synthetic garbage forms massive gyres -- floating trash heaps -- and is killing large numbers of birds, fish and marine animals who ingest it at or near the surface.

But we also know that plastic waste is decomposing into tiny pieces and sinking gradually to the sea bottom. A 2015 study found that a square kilometer -- or 0.62 square miles -- of sea floor contained about 4 billion plastic fibers, an even greater concentration than at the surface.

And now, in a study published in Scientific Reports, British scientists say have found what they say is the first evidence that plastic are getting into the bodies of animals who live at the bottom of the oceans.

Researchers from the universities of Bristol and Oxford, working on the Royal Research Ship (RRS) James Cook, found that tiny fragments of plastic called microbeads are inside hermit crabs, squat lobsters, and sea cucumbers, at depths ranging from 300 meters (984 feet) to 800 meters (2,225 feet).

The scientists examined areas in the mid-Atlantic and southwest Indian Oceans.

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"There appears to be no environment on Earth that has escaped plastic pollution," they write it the article.

The organisms were collected using the manipulator arm and suction hose of a remotely operated vehicle. In addition, the scientists took samples of sediment from the ocean bottom.

In the study, 6 of the 9 deep-sea organisms examined contained tiny bits of plastic waste, lodged in the tentacles, mouth, gills, stomach, and other organs. The scientists believe there is a "high probability" of other numerous other organisms ingesting plastic as well.

"Given the ever-increasing plastic load reaching our oceans, and that a large portion of plastics will likely eventually end up on or buried in the seafloor, the potential is there for an unseen pervasive impact on deep-marine ecosystems," they conclude.

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In a press release, Bristol University zoologist Michelle Taylor, the study's lead author, said the study shows that plastic pollution reaches far from its coastal sources.

"What's particularly alarming is that these microplastics weren't found in coastal areas but in the deep ocean, thousands of miles away from land-based sources of pollution," she said.

It's still unclear what health effects the plastic is having on organisms on the sea floor. Birds, fish and other marine animals are suffering harm from toxic chemicals in the plastic and by plastic particles filling up their stomachs, keeping them from getting nourishment.

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