Magazine article Oceanus

Plastic Particles Permeate the Atlantic

Magazine article Oceanus

Plastic Particles Permeate the Atlantic

Article excerpt

You've heard about the Great Garbage Patch in the Pacific Ocean. Well, the Atlantic certainly isn't pristine when it comes to plastic.

In two major studies published in August 2010, scientists at Sea Education Association (SEA) and Woods Hole Oceanographic Institution (WHOI) analyzed plastic debris skimmed over the past decades from the surface of the Atlantic Ocean. They found that plastic was widespread throughout the western North Atlantic, primarily in fragments measured in millimeters, the size of pencil erasers or smaller.

Chemical analyses of the debris revealed more intriguing findings and posed new questions:

* Since 1986, the global production of plastics has skyrocketed, but the concentration of plastics in Atlantic surface waters has remained about the same. If the amount of plastics entering the oceans has also skyrocketed, what processes might be removing some plastics from surface waters?

* Debris in the surface ocean contained few particles made of certain types of plastic that are abundant on land, specifically polyethylene terepththalate, or PET, which most beverage bottles are made of. What is happening to that plastic?

* The plastic particles showed evidence of being coated with living organisms. Are microbes or other tiny life forms digesting the plastics, causing them to sink, or are they sticking to the particles and being carried through the ocean like sailors on rafts? (See page 22.)

For their studies, the scientists took advantage of a remarkable dataset collected in an unorthodox way. Every year since 1971, SEA, a nonprofit organization based in Woods Hole, Mass., has been taking undergraduate students aboard its ships every year for a 12-week SEA Semester program. Thirteen years later, it began a standard practice for its students to sample along the same track each year, towing nets along the surface twice a day to collect biological samples and ocean debris. This unprecedented effort resulted in roughly 64,000 pieces of plastic collected by 7,000 undergraduates from 6,100 net tows since 1986. It was a scientific treasure trove that researchers could tap to reveal long-term trends in ocean plastics over a wide area of the Atlantic and Caribbean Sea.

"I passed SEA on my way to WHOI every day and never knew they had this extensive, long-term stockpile of data," said WHOI marine chemist Chris Reddy. "When I found out, I started salivating, and we began collaborating to mine it."

A brief history of marine plastics

In 1997, Charles Moore brought widespread attention to the problem of plastics in the ocean when he crossed the North Pacific Gyre in his catamaran Alguita on the way back home to California from Hawaii. He found surprisingly large amounts of plastic debris (sometimes hyped in the media as a an island of floating plastic as large as Texas that you can walk on for miles and miles). He became an important advocate for cleaning up the oceans.

But high concentrations of plastic debris were first reported from the Atlantic Ocean, specifically the Sargasso Sea, by two WHOI scientists, Edward J. Carpenter and K.L. Smith Jr., in 1972. Aboard WHOI's research vessel Atlantis II, they collected, counted, and weighed all the plastic pieces collected in a net with a 1-meter-wide mouth that was towed at the ocean surface.

Carpenter and Smith calculated concentrations of 50 to 12,000 plastic particles, collectively weighing up to 1,070 grams, per square kilometer. The highest numbers were obtained at about 34[degrees]N latitude in the Sargasso Sea. Later work showed that plastic debris was widespread throughout the northwestern Atlantic, and that densities could be much higher.

For its routine plastic sampling, SEA incorporated methods comparable to those used by the WHOI scientists in the early 1970s--tow a 1-meter-wide net through the surface and collect, count, and weigh the plastic particles trapped inside. …

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