Once in the water debris can be blown by the wind or carried by ocean currents. Some of the debris is caught in gyres (circular ocean currents) where it can build up. The Great Pacific Garbage Patch is one such example of this, comprising a vast region of the central North Pacific Ocean (about 700,000 sq km or almost the size of New South Wales).
This area contains more than 3 million tons of plastic meaning that there are approximately six kilograms of plastic for every kilogram of plankton per cubic meter of seawater. As well as plastics there are high amounts of chemical sludge and other debris. Most of this waste material is drawn from coastal waters off North America and Japan.
Map showing location of Great Pacific Garbage Patch
(marked in black)
The next biggest known marine garbage patch is the North Atlantic Garbage Patch, estimated to be hundreds of kilometres across in size. In all, there are six areas of gyres where marine debris may be held for ten years or more.
Since 1986, the Ocean Conservancy has coordinated the International Coastal Cleanup (ICC) – an annual volunteer cleanup of debris along coastlines, rivers and lakes in the USA . Volunteers collect debris items and complete a “Marine Debris Data Card” to record their findings.According to the ICC, over a 20-year period (1986 – 2005), the 10 most frequently collected marine debris items were: