Mid-Pacific Gyre

Category: Marine and Oceanic Biomes.Geographic Location: Pacific Ocean.Summary: The Mid-Pacific Gyre contains a
vast floating mass of plastic and other human debris that creates a major environmental hazard for seabirds, sea turtles, and sea mammals—

and potentially for humans through the oceanic food chain.

Mid-Pacific Gyre 833

One of the five vast oceanic gyres, or roughly circu- lar current systems, the structure of the Mid-Pacific Gyre is formed by four major currents. Together, they rotate through the entire North Pacific Ocean in a generally clockwise motion. The currents— North Equatorial, Kuroshio, North Pacific, and Cal- ifornia—stretch for thousands of miles, influenced by and influencing air and water temperature, humidity, air pressure, and the biota that inhabit the Pacific, its islands, and continental shorelines.

In more detail: The California Current moves toward Central America to meet the North Equa- torial Current on the Mexican Coast before head- ing to Asia as the North Equatorial Current. From these equatorial waters and along the coast of Japan, the system picks up warmth as it becomes the Kuroshio Current. This segment flows north- eastward to confront the cold subarctic Oyashio

Thousands of pieces of plastic washed up along a beach in Hawaii in August 2008. The nearby North Pacific gyre helps bring this debris to Hawaii. (NOAA/Eric Johnson)

834 Mid-Pacific Gyre

current; their merger fuels the warm North Pacific Current, which flows across to its encounter with North America, where it splits into the north- bound Alaska Current and the California Current, completing the gyre.

With few major island chains or continental masses, and with generally low winds, the surface water of the gyre tends to push floating matter toward its low-energy center. In recent decades, this trend has precipitated a phenomenon that has been variously dubbed the Trash Vortex, the Great Pacific Garbage Patch, the Eastern Garbage Patch, and other monikers.

This vast extent of mostly human-generated debris is composed of up to 90 percent polymer or plastic materials. Generally the mundane products of consumer society, the leading recorded items include plastic bottles, cups, bags, and packing materials. Some estimates are that up to 10 million tons of plastic materials enter the world’s oceans each year; perhaps one-quarter to one-third of this flotsam finds its way ultimately to this vortex. While much of the material degrades into smaller particles, virtually none of it is naturally recyclable into the environment. Instead of decomposing, then, it remains a threat for marine organisms of many sizes and scales.

Although this diffuse Pacific Ocean garbage patch was first observed in the 1970s, it came to wide public attention in 1997 when Captain Charles Moore, founder of the Algalita Marine Research Foundation of Long Beach, California, observed the mass and began to take measure- ments. In many samples scooped out of the ocean, Moore discovered that there were six times more plastic in the water than plankton.

Aquatic Danger

The garbage gyre presents a dire threat—beyond the disturbing appearance of floating trash such as fishnets, clothing, bottles, plastic bags, and ciga- rette lighters. Believing that the larger items are prey or plants, many seabirds and sea turtles eat the plastic—which in many cases has absorbed toxins during its manufacture, its intended use, and/or after disposal. Digestive processes can release many such toxins. The chips of plastic also

can cause digestive, pulmonary, and/or respira- tory blockage that eventually kills the creature that ingests it.

In this way, dead fish, birds, and marine mam- mals also become caught up in the vortex. Scien- tists have estimated that around the world, more than 1 million seabirds and in excess of 100,000 mammals and sea turtles die each year from ingest- ing plastic that floats out to sea. Jellyfish, too, may eat the poisoned debris; they in turn are eaten by fish. When fish containing the concentrated and released toxins are caught by commercial fishers, those fish can then taint the human food chain.

In the summer of 2010, a team of scientists from Woods Hole, Massachusetts, recovered 20,000 bits of floating plastic per square mile (2.6 square kilometers) from the Great Garbage Patch, giving some idea of the scope and intensity of the problem.

While plastics and polymers are the chief com- ponent of the Great Garbage Patch, this is by no means the only problem. Commercial fishers who use 20-mile (32-kilometer) castaway fishnets snare everything in their nets from dolphins to sea turtles, which after being discarded as worth- less by-catch, then in turn become debris heading toward the patch.

The problem of floating garbage also exists in the North Atlantic Ocean, to a somewhat lesser extent. Between 1986 and 2008, scientists collected 64,000 tiny particles of plastic from the Atlantic. Another large area known as the Western Garbage Patch lies off the coast of Japan. Other researchers believe that the biggest patch of all may be located in the South Pacific, but no dedicated scientific examination of that area has been undertaken.

In addition to the plastic and debris that end up in various surface garbage patches of the world’s oceans, researchers believe up to 70 percent of ocean debris sinks to the bottom, winding up on the ocean floor. No one is sure what havoc that debris may be creating for the ecosystems deep in the oceans.

Mitigation and Prevention

Many scientists believe that the only solution to the issue of floating garbage vortices is to pre-

vent plastic and other debris from ending up in the ocean in the first place. Even if that task were accomplished, it is possible that current damage could persist for thousands of years, because plas- tic does not decompose.

Raising and activating public awareness will be crucial to get anything meaningful done about this threat. Environmentalist Moore, still active more than 15 years after his first discoveries, has concentrated his efforts on investigating the phenomenon, and informing both the scientific community and the public about the extent of the problem. Moore and his Algalita Foundation team, always seeking to better map the garbage gyre, think that it may be 100 feet (30 meters) deep or more.

Various suggestions for keeping plastic out of the ocean include recycling and reusing plas- tic, opting for items that use fewer or no plastic materials in either content or packaging, and ini- tiating local cleanup activities on all the beaches, estuaries, lagoons, and marine coasts and water- ways of the world. In one such local effort, for example, Mary Crowley, who owns a California- based boat-chartering business, in 2010 launched Project Kaisei to call attention to the Great Gar- bage Patch by assembling a team of volunteers to begin hauling debris away from the patch one boatload at a time.

Elizabeth Rholetter Purdy

Further Reading

Blomberg, Lindsey E. “The Great Pacific Garbage Patch.” Environmental Magazine 22, no. 3 (2011).

Coe, James M. Marine Debris: Sources, Impacts, and Solutions. New York: Springer, 1997.

Greenpeace. “The Trash Vortex.” http://www .greenpeace.org/international/en/campaigns/ oceans/pollution/trash-vortex.

Kostigen, Thomas M. “The World’s Largest Dump: The Great Pacific Garbage Patch.” Discover, July 2008. http://discovermagazine.com/2008/jul/10 -the-worlds-largest-dump.

Perkins, Sid. “Oceans Yield Huge Haul of Plastic.” Science News 177, no. 7 (2010).