we feed on fish that feed on
OCEAN PLASTIC PARTICLES
by
RACHEL NUWER
_________________________________________________
Rachel
Nuwer is a freelance science journalist . She contributes to the
New York Times, Smithsonian, Scientific American, New Scientist,
Popular Science, Audubon Magazine, and blogs for Smithsonian,
where this report originally appeared.
Plastic
is the most pervasive pollutant in the ocean today. But researchers
have struggled to estimate just how much of the six billion tons
of plastic that has been manufactured since the mid-20th century
ultimately winds up in the ocean.
Now a
carefully vetted estimate of our oceans’ plastic burden
shows that the answer is not pretty. Based on the calculations,
at least 5.25 
trillion
pieces of plastic -- weighing nearly 269,000 tons -- are currently
bobbing around in the ocean. A team of researchers from six countries
reported the finding in PLOS ONE.
Revealing
this disturbing figure required the team to conduct 24 garbage-collecting
expeditions between 2007 and 2013. Those trips to sea included
visits to all five sub-tropical gyres -- large systems of constantly
rotating currents infamous for their roles in creating garbage
patches -- plus the Mediterranean Sea, the Bay of Bengal and Australia.
At all of the sites, teams collected water samples for estimating
the amount of microplastic, pieces of plastic smaller than 4.75
millimeters. They also tallied up larger pieces using standardized
visual surveys. These data represent the most comprehensive tally
yet done for ocean plastic pollution.
With
their field data in hand, the researchers created a computer model
to estimate the total quantity and weight of the world’s
marine plastic. The model assumed that plastic entered the ocean
via rivers, coastlines and ships, and it took factors like wind-driven
vertical mixing, currents and the amount of plastic that winds
up on the ocean floor into account. The team also corroborated
their estimates with field tests.
In addition
to the weight estimate, the team made an important and frightening
observation: Large pieces of plastic tended to be most concentrated
near coasts, but the smallest particles they measured -- from
the size of a grain of sand to a grain of rice -- accounted for
about 90 percent of the total garbage count. It seems that plastic
gets chewed into microplastic once it hits an ocean gyre, where
it is broken down by a combination of waves, ultraviolet radiation
from the sun, oxidation and nibbling fish. Given these findings,
ocean garbage patches may be more aptly named garbage blenders.
To make
matters worse, the newly created microplastic doesn't stay put,
but instead gets spewed from the gyre into the greater ocean.
Every water sample the researchers took, no matter how remote,
was laced with some amount of microplastic. The team was shocked
to discover multitudes of microplastic near the subpolar gyres,
for example, corroborating recent findings that high amounts of
the humanmade material can also be found in sea ice.
The extreme
reach of plastic pollution is a problem, because those barely
noticeable pieces can bind to pollutants and, when ingested by
marine animals, can act as mini toxic bombs, gut-clogging confetti
or both. As Marcus Eriksen, director of research for the 5 Gyres
Institute and lead author of the study, told PLOS: “The
endgame for micro-plastic is interactions with entire ocean ecosystems.”
