April 26, 2012
Plastic Waste In Oceans Severely Underestimated
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Oceanographers may be severely undercounting the true amount of plastic waste that finds its way into the oceans after a happenstance discovery of how the plastic is actually distributed.
On a research cruise, University of Washington oceanographer Giora Proskurowski noticed the water surface was littered with tiny bits of plastic, until noticing the that as the wind picked up the plastic “disappeared.” Water samples taken from 16 feet below the surface found the wind pushing the lightweight plastic particles below the surface, writes Nancy Gohring of the University of Washington.
This discovery meant that decades of research into how much plastic litters the ocean, conducted by skimming only the surface, may in some cases vastly underestimate the true amount of plastic debris in the oceans, Proskurowski wrote in Geophysical Research Letters this month.
Proskurowski and University of Delaware co-author Tobias Kukulka, said that data collected from just the surface of the water commonly underestimates the total amount of plastic in the water by an average factor of 2.5. In high winds the volume of plastic could be underestimated by a factor of 27, UPI reports..
“That really puts a lot of error into the compilation of the data set,” Proskurowski said. “By factoring in the wind, which is fundamentally important to the physical behavior, you´re increasing the rigor of the science and doing something that has a major impact on the data.”
Plastic waste in the oceans is a concern as it harms fish and sea life who ingest it mistaking the tiny bits for plankton and brine. The particles also make nice homes for bacteria and algae, which are then transported along with the particles into different regions of the ocean where they may be invasive and cause problems.
Proskurowski gathered data on a 2010 North Atlantic expedition where he and his team collected samples at the surface, plus an additional three or four depths down as far as 100 feet.
The team plans to publish a “recipe” that simplifies the model to encourage the wide range of groups investigating ocean plastics to find some consistency among the studies, he said.
“On this topic, what science needs to be geared toward is building confidence that scientists have solid numbers and that policy makers aren´t making judgments based on CNN reports,” he said.
Descriptions of the so-called great Pacific garbage patch in widespread news reports may have led many people to imagine a giant, dense island of garbage while in fact the patch is made up of widely dispersed, millimeter-size pieces of debris, explained Proskurowski.
In the future, Proskurowski hopes to examine additional factors, including the drag of the plastics in water, complex ocean turbulence and wave height, that might improve the accuracy of the model. He also may have the chance to examine the relationship between wind speed and depth of plastic particles.
The 2010 expedition had near-uniform wind conditions so the researchers were unable to test that relationship.
Image 1: Pieces of plastic debris found in the oceans are smaller than many people think. Most are measured in millimeters. Credit: Sea Education Association
Image 2: Giora Proskurowski deploys a net to collect samples that help estimate how much plastic debris is in the ocean. Credit: Sea Education Association