Plastics at sea create raft of problems | Science News for Students

Plastics at sea create raft of problems

About 269,000 metric tons of plastic pollute the world’s oceans, a new study estimates
Jan 7, 2015 — 7:00 am EST
piece of plastic from ocean

A piece of plastic scooped from the North Atlantic Ocean. It shows the tell-tale bite marks of a fish. A new study estimates how much plastic floats throughout the world’s oceans — trash that puts many marine creatures at risk.

Stiv Wilson

If you could somehow weigh all the plastic floating in the world's oceans, it would equal the mass of roughly 38,000 African elephants.

That estimate comes from a new global study of plastics floating in the oceans. After six years of research, scientists estimate the seas contain about 5.25 trillion pieces of this trash. Its combined weight: an estimated 269,000 metric tons.

“We found plastics are widely distributed across all oceans,” says Marcus Eriksen. This environmental scientist is part of a research team that published a December 10 paper in PLOS ONE. Eriksen works with the 5 Gyres Institute in Los Angeles, Calif. This group looks for solutions to problems caused by plastic trash.

fish dissectionScientists find the extent of the ocean’s plastic trash problem worrying. Fish and other marine organisms can ingest tiny plastic fragments. This trash can then move up the food chain as seabirds, seals and other marine predators eat those fish.

Plastic is harmful for another reason, too. Previous studies have shown that plastics can work like sponges, soaking up and storing toxic chemicals. These include PCBs, pesticides and flame retardants. When ingested, such plastic can release the pollutants, triggering health problems. A 2013 study showed that such ocean plastics also provide homes for germs, some of which can cause disease.

Eriksen and his team travelled more than 50,000 nautical miles while making their measurements. They surveyed five subtropical gyres. These are large areas of rotating currents. Floating plastic accumulates in these large circular loops. The team also measured concentrations of plastic off the coast of Australia, on the Bay of Bengal and in the Mediterranean Sea.

The experts used a fine mesh net to capture plastic particles smaller than 4.75 millimeters (0.18 inch). Later, they weighed all the tiny bits.

The researchers found that more than half of the weight of all ocean plastics is made up of such tiny pieces. This discovery concerned the team because smaller particles have a greater surface area. This allows them to absorb more pollution per unit weight than larger pieces will.

But bigger pieces also are a problem. Plastic bags, six-pack rings for canned drinks and fishing nets — all can entangle sea birds, turtles and even whales.

A wide range of sources

Bigger pieces of floating plastic tend to come mostly from lost fishing nets and buoys, the study found. The researchers did not weigh these pieces. Instead they counted them (from the comfort of their boats), and noted their sizes. Later, the researchers matched these large pieces with similar-sized ones that they already had weighed.

"These gyres shred large plastics into smaller ones," Eriksen now reports.

As plastic rides atop the gyres' swirling currents, sunlight embrittles it. Waves then can break the pieces into smaller and smaller bits. Oxygen at the water's surface reacts with the plastic. This, too, helps to fragment the bits of plastic trash.

Later, currents eject these tiny bits of plastic from the gyre. Plastic also can escape the gyres as filter-feeding fish and whales swallow snippets of the trash. These creatures feed by opening their mouths to take in tiny floating plants and animals. Floating plastic will be ingested along with the food.

Eriksen would like companies that use plastic in their products to set up systems to recycle those plastics when they become trash. Many recycling programs already exist. Usually they are for products made entirely of plastic, such as bottles. Bicycles, board games and other products that contain some plastic usually are not, however, recycled.

Eriksen also would like to see governments pay fishermen to bring back lost nets and buoys that they find floating in the ocean.

Chelsea Rochman is a marine ecologist at the University of California, Davis. She is concerned by how much plastic Eriksen's team found.

"Hundreds of species become entangled in this debris or mistake it for a meal," she says. Marine creatures entangled in plastic often die, Rochman says. And "eating plastic can physically harm an animal by cutting the digestive tract and getting stuck in the gut," she notes. So even if ocean plastics weren't polluted with toxic chemicals, this trash can still pose a serious threat to creatures that eat it.

Power words

buoy  A floating device anchored to the bottom of a body of water. A buoy may mark channels, warn of dangers or carry instruments to measure the environment.

debris  Scattered fragments, typically of trash or of something that has been destroyed. Space debris includes the wreckage of defunct satellites and spacecraft.

ecology  A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

embrittle     To make brittle.

filter feeder  A water-dwelling animal that collects its nutrients or prey by filtering them out of the water. Some of the best known examples are bivalves, such as clams and mussels. But some whales use long plates of baleen to essentially do the same thing. They suck in water and then use their filtering structures to catch and retain edible materials that had been in the water.

flame retardants   Chemical coatings added to products, such as pyjamas, plastics, foam and furniture, to suppress or delay how fast they might burn in a fire.

germ  Any one-celled microorganism, such as a bacterium, fungal species or virus particle. Some germs cause disease. Others can promote the health of higher-order organisms, including birds and mammals. The health effects of most germs, however, remain unknown.

gyre (as in the ocean)  A ringlike system of ocean currents that rotate clockwise in the Northern Hemisphere and counter clockwise in the Southern Hemisphere. Many of the biggest, most persistent gyres have become collection sites for floating long-lived trash, especially plastic.

ingest   To eat or deliberately bring nutrients into the body by mouth for digestion in the gut.

marine   Having to do with the ocean world or environment.

marine ecologist   A scientist who studies the ocean's ecology.

nautical mile    A unit of measurement for distances at sea, which equals 1.15 miles on land. A nautical mile is determined by the circumference of the Earth at the equator (1 nautical mile being 1 minute — or 1 60th of a degree of longitude — at the equator).

plastic   Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.

polychlorinated biphenyls (PCBs)   A family of 209 chlorine-based compounds with a similar chemical structure. They were used for many decades as a non-flammable fluid for insulating electrical transforms. Some companies also used them in making certain hydraulic fluids, lubricants and inks. Their production has been banned in North America and many countries throughout the world since around 1980.

pollutant   A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

recycle  To find new uses for something — or parts of something — that might otherwise by discarded, or treated as waste.

sea   An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

toxic  Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.

NGSS: 

  • MS-ESS3-3
  • HS-ESS3-3

Further Reading

B. Brookshire. "Mailing off my microbeads." Science News for Students. July 21, 2014.

J. Raloff. "Home, plastic home." Science News for Students. July 16, 2013.

E. Wagner. “Whale of a lesson.” Science News for Students. March 7, 2013.

S. Ornes. “Cleaning clothes dirties oceans.” Science News for Kids. Oct. 5, 2011.

J. Raloff. “Synthetic lint ends up in oceans.” Science News. Sept. 14, 2011.

A. Martinez. “Swirling seas of plastic trash.” Science News for Students. June 22, 2011.

Original Journal Source: M. Eriksen et al. “Plastic Pollution in the World's Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea.” PLOS ONE. Vol. 9, December 10, 2014, p. e111913. doi: 10.1371/journal.pone.0111913.