The horse latitudes are known for dead wind. They lie between the 30th and 35th latitudinal parallels, across the globe, above and below the equator. Their name supposedly comes from the days when Spanish merchant ships, bound for the West Indies, would practically screech to a halt upon crossing the area’s threshold and, to lighten their load and conserve water, would push overboard the horses they had brought along.
While they’re no longer the gravesite of countless unfortunate horses, the horse latitudes are now home to a new menace born of unfettered commercial striving: the Great Pacific Garbage Patch.
Fishermen shun it because its waters lack the nutrients to support an abundant catch. Sailors dodge it because it lacks the wind to propel their sailboats.
From Wikipedia, the free encyclopedia
The Garbage Patch is located within the North Pacific Gyre, one of the five major oceanic gyres.
The Great Pacific Garbage Patch, also described as the Eastern Garbage Patch or the Pacific Trash Vortex, is a gyre of marine litter in the central North Pacific Ocean located roughly between 135° to 155°W and 35° to 42°Nestimated to be twice the size of Texas. The patch is characterized by exceptionally high concentrations of suspended plastic and other debris that have been trapped by the currents of the North Pacific Gyre.
Formation
Like other areas of concentrated marine debris in the world's oceans, the Eastern Garbage Patch has formed gradually over time as a result of marine pollution gathered by the action of oceanic currents.
The garbage patch occupies a large and relatively stationary region of the North Pacific Ocean bound by the North Pacific Gyre. The rotational pattern created by the North Pacific Gyre draws in waste material from across the North Pacific Ocean, including the coastal waters off North America and Japan. As material is captured in the currents, wind-driven surface currents gradually move floating debris toward the center, trapping it in the region.
The size of the affected region is unknown, but estimates range from 700,000 km2 to more than 15 million km2, (0.41% to 8.1% of the size of the Pacific Ocean). The area may contain over 100 million tons of debris.
Plastic photodegradation in the ocean
The Eastern Garbage Patch has one of the highest levels of plastic particulate suspended in the upper water column. As a result, it is one of several oceanic regions where researchers have studied the effects and impact of plastic photodegradation in the neustonic layer of water.Unlike debris which biodegrades, the photodegraded plastic disintegrates into ever smaller pieces while remaining a polymer. This process continues down to the molecular level.
As the plastic flotsam photodegrades into smaller and smaller pieces, it concentrates in the upper water column. As it disintegrates, the plastic ultimately becomes small enough to be ingested by aquatic organisms which reside near the ocean's surface. Plastic waste thus enters the food chain through its intense concentration in the neuston.
The eastern garbage patch cannot be characterised as a continuous visible field of densely floating marine debris. The process of disintegration means that the plastic particulate in much of the affected region may be too small to be seen. In many areas of the affected region, the overall concentration of plastics was greater than the concentration of zooplankton by a factor of seven.
What does exist in the gyres is a great variety of filter-feeding organisms that prey on the ever-renewed crop of tiny plants, or phytoplankton. Each day the phytoplankton grow in the sunlit part of the water, and each night they are consumed by the filter feeders, a fantastic array of alien-looking animals called zooplankton. The zooplankton include chordate jellyfishes known as “salps,” which are among the fastest-growing multicellular organisms on the planet. By fashioning their bodies into pulsating tubes, the salps are able, each day, to filter half the water column they inhabit, drawing out the phytoplankton and smaller zooplankton for food. But salps are gelatinous creatures with a low biomass, and so there is no market for them, either. Hence the realm they dominate, one of the largest uniform habitats on the planet, remains unexploited and largely unexplored.
If something isn't done, he says, the island will increase in size by a factor of ten every two to three years — making in time something more akin to an actual, solid island. "The consequence of putting that much stuff shading the surface of the ocean is unknown," he says. "We don't know the harm."
Yet you can’t see it in satellite photos, because the debris is more “soup” than continent. Instead of forming a trash island, a literal wasteland on the surface, plastic fragments permeate the sea to great depths.
As for a technological solution, something like a fleet of ships to scrape up the mess, is well intentioned, but the size and the fact that this material is mixed into the water column makes for an impossibly large area, about five million square miles.
Curtis Ebbesmeyer, an oceanographer and leading authority on flotsam, has tracked the build-up of plastics in the seas for more than 15 years and compares the trash vortex to a living entity: "It moves around like a big animal without a leash." When that animal comes close to land, as it does at the Hawaiian archipelago, the results are dramatic. "The garbage patch barfs, and you get a beach covered with this confetti of plastic," he added.
The "soup" is actually two linked areas, either side of the islands of Hawaii, known as the Western and Eastern Pacific Garbage Patches. About one-fifth of the junk – which includes everything from footballs and kayaks to Lego blocks and carrier bags – is thrown off ships or oil platforms. The rest comes from land.
The Great Pacific Garbage Patch is particularly dangerous for birds and marine life. Sea turtles mistake clear plastic bags for jellyfish. Birds swoop down and swallow indigestible shards of plastic. The petroleum-based plastics take decades to break down, and as long as they float on the ocean's surface, they can appear as feeding grounds. These animals die because the plastic eventually fills their stomachs. It doesn't pass, and they literally starve to death. A Greenpeace report found that at least 267 marine species had suffered from some kind of ingestion or entanglement with marine debris.
The slowly rotating mass of rubbish-laden water poses a risk to human health, too. Hundreds of millions of tiny plastic pellets, or nurdles – the raw materials for the plastic industry – are lost or spilled every year, working their way into the sea. These pollutants act as chemical sponges attracting man-made chemicals such as hydrocarbons and the pesticide DDT. They then enter the food chain. What goes into the ocean goes into these animals and onto your dinner plate. It's that simple.
Bottle caps and other plastic objects are visible inside the decomposed carcass of this Laysan albatoss on Kure Atoll, which lies in a remote and virtually uninhabited region of the North Pacific. The bird probably mistook the plastics for food and ingested them while foraging.
No comments:
Post a Comment