THE Pacific gyre is a well-known graveyard for plastic. That oceans currents conspire to sweep flotsam into an area south of Hawaii variously described as being from the size of Texas to the size of the United States. Its Atlantic equivalent is less well known, but the currents conspire here, too, to create a zone south of Bermuda into which the detritus discarded by North Americans tends to spiral. In both cases this is bad news for sea creatures, and pictures of choked dolphins and strangled turtles are regularly used to wring the withers of uncaring consumers in the hope that they might use less packaging. The amount of plastic produced around the world increased fivefold between 1976 and 2008, and the amount thrown away by Americans went up fourfold between 1980 and 2008. It is a reasonable assumption that, as the amount of discarded plastic increases, so will the problem of oceanic pollution. Reasonable but, as it turns out, wrong. For a 22-year-long study of the North Atlantic and the Caribbean, just published in Science, suggests things are not getting worse. Kara Law from the Sea Education Association in Woods Hole, Massachusetts, and her colleagues have found that between 1986 and 2008 there was no increase in the concentration of plastic in the areas they looked at. Their study drew on the work of 7,000 undergraduate students and scientists who took part in 6,100 tows across the ocean surface with plankton nets. They collected 64,000 pieces of plastic, all of which were picked by hand from the nets and recorded. As the map shows, plastic tends not to accumulate near the land (from which, presumably, it has been cast) but, rather, gathers offshore. The Sargasso Sea, where floating seaweed accumulates and legend has it that ships thus founder, is also a result of this phenomenon. As the graph shows, though, the amount of floating plastic shows no upward trend. Dr Law and her colleagues have no explanation for this lack of accumulation. A programme by the American plastics industry, begun in 1991, to recapture the spilled resin pellets that are the basic material of the industry, and to prevent their spillage in the first place, has resulted in a decrease in the number of pellets in the water. That alone, however, is insufficient to explain the data. Nor does the missing plastic seem to have sunk. Trawls at depth show no sign of it. The Sargasso Sea of legend, and its modern equivalent, the Bermuda Triangle, are supposed to be places where things disappear without trace. Dr Law seems to have come up with a real example.
Posted on: Fri, 07 Mar 2014 16:20:49 +0000