North of the equator, in the sub-tropical zone of the Pacific that includes the Hawaiian Islands, there is a vast system of rotating currents called the North Pacific Gyre. The Gyre encompasses virtually all of the north Pacific Ocean.
Try an experiment. Take a bowl of water and sprinkle some pepper in it. Cover the whole surface. Now put your finger in the water near the edge of the bowl, and start swirling it around the bowl, near the edge. The pepper all becomes concentrated in the centre of the bowl.
The same thing happens with these oceanic gyres, but instead of pepper, out the oceans we find garbage, mostly plastic of various types and sizes, from shopping bags and six-pack rings to the tiny granules used in some exfoliating skin care products.
Estimates of the size of this “Great Pacific Garbage Patch” vary, from about the size of Texas (to twice the size of the continental United States. However, these estimates are very difficult to make, and confirm.
Ideally, a square kilometer of seawater should contain no plastic. In the garbage Patch, though, there is over 5 kg of plastic debris per square kilometer. In one study, there was plastic debris found in 100 consecutive samples taken over a 1700km path. Though this may not sound like much, there is 5 times as much trash in the surface waters as there is plankton.
It is not know where all this plastic comes from. Some estimates have the majority of it coming from land-based sources, and likely blown by the wind, or from ships. A typical cruise ship generates 8 tons of solid waste every week, all of which gets dumped, and eventually winds up in the garbage patch.
Plastic doesn’t biodegrade, it doesn’t rot. But it does photodegrade. Sunshine will break plastic down, into smaller and smaller pieces of plastic. In fact, most of the trash in the vortex is this sort of confetti-like plastic, which is not readily visible from the deck of a boat or in aerial or orbital images. Eventually, these pieces become small enough to be ingested by the very small organisms at the base of the food chain, and these complex polymers thus enter the food chain.
Eating plastic is bad enough, but these bits of plastic can often have other effects. Some of the components released when plastic degrades include a grab-bag of hazardous chemicals, including PCB and other very toxic compounds. Some plastics can also mimic estradiol, a female hormone, with serious consequences. These organisms can be consumed by other organisms, and toxins accumulate in the food chain.
Eventually, the bio-accumulation of these toxins can affect humans, too. Humans are apex predators, and the PCBs and other chemical sludge build up to the point where people can be affected as well.
Unfortunately, the Great Pacific Garbage Patch is not unique, and a similar, though smaller, waste vortex exists in the Atlantic as well.
Given the area involved, a cleanup would seem to be a monumental task. However, despite that, people are looking to effect a cleanup. Several organizations have been formed with the intent to clean up the Garbage Patch, or at least draw attention to the problem, including the Environmental Cleanup Coalition, the JUNK raft project, and others.
Awareness of the problem, and its root causes, is the first step. Cleanup must, and will, go and-in-hand with any new understanding of the world’s largest toxic waste spill.