It
is no secret that the world’s oceans are swimming with plastic debris —
the first floating masses of trash were discovered in the 1990s. But
researchers are starting to get a better sense of the size and scope of
the problem.
A study
published Wednesday in the journal PLOS One estimated that 5.25
trillion pieces of plastic, large and small, weighing 269,000 tons,
could be found throughout the world’s oceans, even in the most remote
reaches.
The
ships conducting the research traveled the seas collecting small bits
of plastic with nets and estimated worldwide figures from their samples
using computer models.
The largest source of plastic by weight comes
from discarded fishing nets and buoys, said Marcus Eriksen, the leader
of the effort and co-founder of the 5 Gyres Institute, a nonprofit group that combines scientific research with antipollution activism.
Dr.
Eriksen suggested that an international program that paid fishing
vessels for reclaimed nets could help address that issue. But that would
do nothing to solve the problem of bottles, toothbrushes, bags, toys
and other debris that float across the seas and gather at “gyres” where
currents converge.
The pieces of garbage collide against one another
because of the currents and wave action, and sunlight makes them
brittle, turning these floating junkyards into “shredders,” he said,
producing smaller and smaller bits of plastic that spread far and wide.
When
the survey teams looked for plastics floating in the water that were
the size of grains of sand, however, they were surprised to find far
fewer samples than expected — one-hundredth as many particles as their
models predicted. That, Dr. Eriksen said, suggests that the smaller bits
may be swept deeper into the sea or consumed by marine organisms.
The result echoed that of a paper published this year
in Proceedings of the National Academy of Sciences that found a
surprisingly low amount of small plastic debris. Those researchers
estimated as much as 35,000 tons of the smaller debris were spread
across the world’s oceans, but they had expected to find millions of
tons.
Andrés
Cózar, a researcher from the University of Cadiz who headed that study,
said in an email that he and Dr. Eriksen came to different conclusions
about the amount of plastic afloat, but that “it is evident that there
is too much plastic in the ocean,” adding, “The current model of
management of plastic materials is (economically and ecologically)
unsustainable.”
The
fact that the small plastics are disappearing is hardly good news. In
fact, it could be far more troubling than the unsightly mess the
plastics cause. Plastics attract and become coated with toxic substances
like PCBs and other pollutants. Researchers are concerned that fish and
other organisms that consume the plastics could reabsorb the toxic
substances and pass them along to other predators when they are eaten.
“Plastics
are like a cocktail of contaminants floating around in the aquatic
habitat,” said Chelsea M. Rochman, a marine ecologist at the University
of California, Davis. “These contaminants may be magnifying up the food
chain.”
The
ocean studies make an important contribution to the understanding of
the floating waste problem, said Nancy Wallace, director of the marine debris program for the National Oceanic and Atmospheric Administration.
Further
research should look beyond the surface to test where the smaller
plastic bits might have gone: into the deeper ocean depths, along the
shoreline or settled on the seafloor. “It’s premature to say there is
less plastic in the ocean than we thought,” she said. “There may just be
less where we’re looking.”
Dr.
Eriksen said the scope of the problem makes floating garbage collection
impractical. His group has had some success with campaigns to get
manufacturers of health and beauty aids to stop using small scrubbing beads of plastic in their products.
Manufacturers
of other products, he said, must be urged to change their practices as
well. “We’ve got to put some onus on producers,” he said. “If you make
it, take it back, or make sure the ocean can deal with it in an
environmentally harmless way.”
Dr.
Wallace agreed. “Unless we can stop the flow — turn off the tap of
these pieces of debris going into the ocean all the time — we’re not
going to be able to stop the problem.”
The
American Chemistry Council, which speaks for the plastics industries,
issued a statement saying that its members “wholeheartedly agree that
littered plastics of any kind do not belong in the marine environment,”
and it cited industry efforts to combat the problem, including the 2011
Declaration of the Global Plastics Associations for Solutions on Marine
Litter, which has led to 185 projects around the world.
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