Waterlogged plastic bags look like jellyfish to feeding turtles. Seabirds mistake raw plastic pellets spilled from container ships for fish eggs. Plastic sheeting has even been found in the stomachs of dolphins and whales. (Once lodged in an animal's digestive tract, plastic can prove fatal.)
While most plastics are non-biodegradable, Thompson says the action of waves and the elements work to break plastic objects down into fragments tiny enough to be ingested by countless other marine organisms.
To test the potential for this to occur, Thompson and his colleagues kept barnacles, lugworms, and detritus-eating amphipods in aquaria with small amounts of microscopic plastics. These invertebrates all ingested the fragments within a few days.
Thompson highlights two possible environmental impacts that his team will investigate over the next three years. "One is that these smaller fragments could cause blockages to the feeding apparatus and the digestive tract [of marine invertebrates], just as plastic bags have affected larger animals like turtles," he said.
"The second area we're exploring is the possibility of chemical transfer from plastics to these organisms."
Many plastics contain toxic chemicals, including biocides (to prevent organisms colonizing their surfaces), colorings, and flexibility-enhancing agents known as plasticizers. These substances could be released if the plastics were eaten.
Thompson added: "Another possibility, recently shown by researchers in Japan, is that when plastics are floating in the seas, they will accumulate and absorb toxic chemicals that are present from other sources. These are hydrophobic chemicals that hate to be in water and cling to plastic as an alternative. These chemicals may then be transported to organisms that eat the plastic."
Such toxic chemicals include PCBs (polychlorinated biphenyls) and DDE (dichlorodiphenyldichloroethylene), which are derived from pesticides and other manmade substances. These agents are known endocrine disruptorschemicals that interfere with the reproductive, developmental, and immune systems of animals.
Endocrine disruptors, or so-called "gender benders," have been linked to the masculization of female polar bears, egg development in male flatfish, and spontaneous abortions and declines in seal populations.
Other recent studies likewise suggest that vast quantities of microscopic plastics are building up in our oceans. For example, researchers from the Algalita Marine Research Foundation in Long Beach, California, found that the mass of plastic fragments in parts of the central Pacific Ocean is six times greater than that of resident plankton.
Thompson said he has catalogued plastic debris in many parts of world, including a space rocket tail-cone washed up on a beach on the Caribbean island of St. Lucia.
"Plastics have a wide range of indispensable uses, from telephones to radio sets, but those aren't the products we're finding on the beaches," he said. "What we are finding, increasingly, are plastic bottles, caps, bits of packagingdisposable items which are used once and then thrown away."
This view is supported by the results of the U.K.'s biggest annual beach litter survey, published last month by the Marine Conservation Society. Conducted last September, 2,600 volunteers beach-combed 135 kilometers (84 miles) of coastline.
Beach-goers were found to be the biggest polluters, contributing 36.7 percent of litter found. Plastic items made up more than half of the total trash recovered. This included 5,831 plastic bagsthe equivalent of 43 bags for each kilometer (0.6 mile) of coastline surveyed. Andrea Crump, a litter projects coordinator with the Marine Conservation Society, said: "Every single piece of rubbish has an owner. And every single person can make a difference by making sure they take their rubbish with them when they leave the beach."
Thompson added: "There's a challenge here for all of us to be more careful in the way we use and dispose of plastic."
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