Measuring Microplastics in their Final Resting Place
Recycling plastics have become much more popular around the world, but large amounts are still thrown away. Through the power of wind, gravity, and moving water, much of the globally produced plastics find their way into the oceans. But the plastic bottles we see washing up along the shoreline only tell a small fraction of the marine plastics story. Most plastic debris in the ocean are nearly invisible to the naked eye. These are known as microplastics, and they are far more dangerous to oceanic wildlife than larger plastic debris. After previous studies on this subject have failed to estimate the extent of microplastic pollution in the ocean, a team of researchers has proposed a new set of guidelines for their recording and characterization.
The team consisted of British and Chilean researchers and led by scientists from the German Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.
They first identify the problem that microplastics cause. They are innumerable ultra-small objects that float near the surface, settle on the seabed, or washed onto the beach. They are defined as plastic objects whose diameter is less than five millimeters. Most are actually smaller than a grain of sand and could fit on the tip of a needle.
Being so small, they are easily ingested by marine life and could end up lodged in the animals tissue. Some microplastics can cause serious illness within the animals because toxic substances tend to attach themselves to them. They could potentially work their way through the food chain to the ultimate keystone species, humans.
The team then went about devising a standardized method to characterize and record the extent of microplastic pollution. They analyzed 68 scientific publications on the subject. Very different methods were used, making it difficult to accurately determine the observed regional differences in microplastic distribution. It was unclear whether the differences were real or attributable to differing recording methods.
For example, the studies used nets to collect microplastics out of the water column. A net with a mesh of 85 micrometers could fish out 100,000 times more than a net with 450 micrometers. Standardized methods are required for accurate measurement and comparison.
In the future, the team expects that all researchers will adopt their standardized method. The reliability of their work would increase and well-informed determinations could be made about the fate microplastics in the oceans and their threat to ecosystems and human health.
This study has been published in the journal, Environmental Science and Technology.
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