As much as 10 per cent of plastics produced end up inside giant marine vortexes
Alex Roslin, Canwest News Service 17 Nov 08;
Scientists are growing alarmed about massive floating dumps that are believed to be building up in centres of nearly all of the world's oceans.
The best-known patch, known by some as the Great Pacific Ocean Garbage Patch, consists of an estimated 100 million tonnes of plastic debris that has accumulated inside a circular vortex of currents known as the North Pacific gyre. Environmentalists call it the Pacific Trash Vortex.
It is estimated to be anywhere from 700,000 square kilometres -- an area larger than Alberta -- up to 15 million square kilometres (the size of two Australias), depending on how it is measured. Plastic from the vortex is increasingly washing up on Hawaiian atolls and being found in the guts of seabirds and fish.
An estimated 100,000 marine mammals die each year from eating or being entangled in debris -- mostly plastic -- in the North Pacific alone. Hence the vortex's other nickname: the Plastic Killing Fields.
Plastic in the sea doesn't biodegrade like other garbage. Instead, it slowly breaks up into tinier and tinier pieces that float on the ocean surface or sink to the sea bottom and can take years to reach the ocean gyres.
These vortexes are increasingly seen as environmental disaster zones. Plastic contains many toxic chemicals; it also soaks up other dangerous substances already present in the ocean, like carcinogenic PCBs and DDT.
Eighty per cent of the plastic in the ocean gyres is believed to come from the land, while the remainder is litter from cargo ships, cruise boats and other vessels.
Richard Thompson, a marine biologist at England's University of Plymouth, is one of the few scientists studying plastic in oceans.
In a 2004 study, Thompson found microscopic pieces of plastic in the water that had been scooped up with plankton samples in the North Atlantic starting in the 1960s, but there was four times as much plastic in recent samples, coinciding with a 25-fold increase in plastic production worldwide between 1960 and 2000.
Even more alarming, the water samples were from an area of the Atlantic north of Britain that isn't even in the gyre. No one has studied the amount of plastic in the Atlantic gyre itself.
Ocean currents and winds are slowly bringing debris -- estimated to be 10 per cent of the world's plastic production -- to the centre of five major ocean gyres in the North and South Atlantic, North and South Pacific and the Indian Oceans, said Marieta Francis, executive director of the Algalita Marine Research Foundation, based in Long Beach, Calif.
But despite the ever-growing plastic blobs in other oceans, the Pacific gyre is the only one that has been studied.
The Algalita foundation's founder, a yachter named Charles Moore, chanced upon the Pacific Garbage Patch during a 1997 boat race.
"Here I was in the middle of the ocean, and there was nowhere I could go to avoid the plastic," he told the U.S. News and World Report.
The vortex was in the North Pacific gyre, where a high-pressure zone forces debris into a central area that has low currents and winds.
