(CN) — Photos of plastic clogging the world’s waterways and filling the stomachs of unfortunate sea birds and whales have become common in recent years, and on Tuesday the journal Nature Communications reported on an enormous buildup of frozen plastic particles trapped in Arctic sea ice.
Eight millions tons of plastic debris moves from the land into the oceans each year, and plastic accounts for 73 percent of marine debris worldwide, authors from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research wrote in “Arctic Sea Ice Is an Important Temporal Sink and Means of Transport for Microplastic.”
Microplastics are plastic particles, fibers, pellets and other fragments with a length, width or diameter from only a few of a millimeter to less than 5 millimeters. A considerable amount of microplastic is released into the oceans by the gradual deterioration of larger pieces of plastic.
Microplastics can also be created on land through laundering synthetic textiles or abrasion of car tires. Plastic particles initially float through the air as dust, and are blown to the ocean by the wind, or find passage through sewer networks.
“During our work, we realized that more than half of the microplastic particles trapped in the ice were less than a twentieth of a millimeter wide, which means they could easily be ingested by arctic microorganisms like ciliates, but also by copepods,” research biologist and lead author Dr. Ilka Peeken said.
The observation is a troubling one, she said, because “no one can say for certain how harmful these tiny plastic particles are for marine life, or ultimately also for human beings.”
Ice samples from five regions of the Arctic Ocean contained up to 12,000 microplastic particles per liter of sea ice.
Different types of plastic showed different footprints in the ice, allowing researchers to trace them back to possible sources. One is the massive garbage patch in the Pacific Ocean, and the high percentage of paint and nylon particles pointed to intensified shipping and fishing in some parts of the Arctic Ocean.
The Wegner Institute team gathered the ice samples during three expeditions to the Arctic Ocean on the research icebreaker Polarstern in the spring of 2014 and summer of 2015. They came from five regions along the Transpolar Drift and the Fram Strait, which transports sea ice from the Central Arctic to the North Atlantic.
The Fram Strait is east of Greenland and west of the much smaller island of Svalbard.
The researchers were the first to analyze the ice cores layer by layer, using a Fourier Transform Infrared Spectrometer, which bombards microparticles with infrared light and uses mathematical model to study the radiation they reflect back, to determine the amount and distribution of microplastic in the sea ice.
The particles absorb and reflect different wavelengths, allowing each substance to be identified by its optic fingerprint.
“Using this approach, we also discovered plastic particles that were only 11 micrometers across. That’s roughly one-sixth the diameter of a human hair, and also explains why we found concentrations of over 12,000 particles per liter of sea ice, which is two to three time higher than what we’d found in past measurements,” according to co-author Gunnar Gerdts, in whose laboratory the measurements were carried out.
The researchers found that 67 percent of the particles detected in the ice belonged to the smallest-scale category, 50 micrometers and smaller.
The particle density and composition varied significantly from sample to sample and the plastic particles were not uniformly distributed throughout the ice.
“We traced back the journey of the ice floes we sampled and can now safely say that both the region in which the sea ice is initially formed and the water masses in which the floes drift through the Arctic while growing, have an enormous influence on the composition and layering of the encased plastic particles,” Peeken said.
The researchers also learned that ice floes, driven in the Pacific water masses of the Canadian Basin, contain particularly high concentrations of polyethylene. Polyethylene is most often used in packaging material.
“Accordingly, we assume that these fragments represent remains of the so-called Great Pacific Garbage Patch and are pushed along the Bering Strait and into the Arctic Ocean by the Pacific inflow,” researchers wrote.
In contrast, the scientists predominantly found paint particles from ships’ paint and nylon waste from fishing nets in ice from the shallow marginal seas of Siberia.
“These findings suggest that both the expanding shipping and fishing activities in the Arctic are leaving their mark. The high microplastic concentrations in the sea ice can thus not only be attributed to sources outside the Arctic Ocean. Instead, they also point to local pollution in the Arctic,” Peeken said.
Seventeen types of plastic were found in the sea ice, including packaging materials, paints, nylon, polyester, and cellulose acetate, primarily used to make cigarette filters. These six materials accounted for roughly half of all the microplastic particles detected.
“The sea ice binds all this plastic litter for two to a maximum of 11 years: the time it takes for ice floes from the marginal seas of Siberia or the North American Arctic to reach the Fram Strait, where they melt,” Peeken said.
Sea ice also transports large quantities of microplastic to the waters off the northeast coast of Greenland.
The researchers cannot yet say whether the released plastic particles remain in the Arctic or are transported farther south; it seems likely that the plastic litter begins sinking into deeper waters relatively quickly.
“Free-floating microplastic particles are often colonized by bacteria and algae, making them heavier and heavier. Sometimes they clump together with algae, causing them to drift down to the seafloor much faster,” co-author Dr. Melanie Bergmann said.
Observations made by the institute’s deep-sea network HAUSGARTEN in the Fram Strait lend additional weight to this thesis.
“We recently recorded microplastic concentrations of up to 6,500 plastic particles per kilogram of seafloor; those are extremely high values,” Bergmann said.
Such close study reveals the apparently pristine Arctic seas in a new light. The so-called “bergy bits” — broken off bits of translucent blue and white frozen fresh water that tourist ships often scoop up and add to the drinks of cruise ship passengers — are likely to be chock-full of microplastics.