By Laura Parker
15 July 2014
(National Geographic) – When marine ecologist Andres Cozar Cabañas and a team of researchers completed the first ever map of ocean trash, something didn't quite add up.
Their work, published this month in the Proceedings of the National Academy of Sciences, did find millions of pieces of plastic debris floating in five large subtropical gyres in the world's oceans. But plastic production has quadrupled since the 1980s, and wind, waves, and sun break all that plastic into tiny bits the size of rice grains. So there should have been a lot more plastic floating on the surface than the scientists found.
"Our observations show that large loads of plastic fragments, with sizes from microns to some millimeters, are unaccounted for in the surface loads," says Cozar, who teaches at the University of Cadiz in Spain, by e-mail. "But we don't know what this plastic is doing. The plastic is somewhere—in the ocean life, in the depths, or broken down into fine particles undetectable by nets."
What effect those plastic fragments will have on the deep ocean—the largest and least explored ecosystem on Earth—is anyone's guess. "Sadly," Cozar says, "the accumulation of plastic in the deep ocean would be modifying this enigmatic ecosystem before we can really know it."
But where exactly is the unaccounted-for plastic? In what amounts? And how did it get there?
"We must learn more about the pathway and ultimate fate of the 'missing' plastic," Cozar says.
One reason so many questions remain unanswered is that the science of marine debris is so young. Plastic was invented in the mid-1800s and has been mass produced since the end of World War II. In contrast, ocean garbage has been studied for slightly more than a decade.
"This is new mainly because people always thought that the solution to pollution was dilution, meaning that we could turn our head, and once it is washed away—out of sight, out of mind," says Douglas Woodring, co-founder of the Ocean Recovery Alliance, a Hong Kong-based charitable group working to reduce the flow of plastic into the oceans.
The North Pacific Garbage Patch, a loose collection of drifting debris that accumulates in the northern Pacific, first drew notice when it was discovered in 1997 by adventurer Charles Moore as he sailed back to California after competing in a yachting competition.
Research on marine debris is also complicated by the need to include a multidiscipline group of experts, ranging from oceanographers to solid-waste-management engineers.
"We are at the very early stages of understanding the accounting," says Kara Lavender Law, an oceanographer at the Sea Education Association, based in Cape Cod, Massachusetts. "If we think ten or a hundred times more plastic is entering the ocean than we can account for, then where is it? We still haven't answered that question. […]
Cozar says that one answer to the missing-plastic mystery is that some of the tiniest bits of plastic are being consumed by small fish, which live in the murky mesopelagic zone, 600 feet to 3,300 feet (180 to 1,000 meters) below the surface. Little is known about these mesopelagic fish, Cozar says, other than that they're abundant. They hide in the darkness of the ocean to avoid predators and swim to the surface at night to feed.
"We found plastics in the stomachs of the fishes collected during Malaspina's circumnavigation," he says. "We are working on this now." [more]