Microplastics locked up in the Arctic will be re-released into the world's oceans as climate change melts sea ice. Such plastic pollution could have broad consequences for marine — and human — life.
Researchers at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), in Bremen have discovered higher amounts of microplastic in Arctic sea ice than have ever been recorded at the polar reaches of the earth.
The ice samples from five regions of the Arctic Ocean contained up to 12,000 microplastic particles per liter of sea ice. That's a lot of plastic for sea ice lodged in some of the world's most-remote regions.
But where is it coming from? Possible sources of the plastic include the massive garbage patch in the Pacific Ocean; while evidence of paint and nylon particles points to intensified shipping and fishing activities in parts of the Arctic Ocean.
A plastic planet
While a study in 2014 showed evidence of microplastic in Arctic sea ice after individual samples were taken, this is the first time infrared imaging has been used at the source to analyze entire areas of ice. This has allowed AWI researchers to find a much higher concentration of tiny plastic particles than previously thought.
Although evidence of microplastic particles in the world's oceans has been found as far back as the 1970s, since the mid-2000s there has been an "explosion" of research into the impacts of microplastics, according to Chelsea Rochman, an assistant professor in the biology department at the University of Toronto.
Read more: Microplastics endanger whales and sharks
Rochman is one such researcher who has studied the effect of "anthropogenic debris" on hundreds of species of wildlife, and in particular the way this plastic waste has raised toxicity levels in seafood.
But this latest research has amplified his concerns.
"With climate change, this suggests that sea ice melt likely is releasing large quantities of microplastics into the environment," Rochman told DW.
"We often think about methane releases with ice melting; but now we should also be considering microplastics," Rochman continued.
"It seems sea ice was an ultimate sink, and that melting is altering that fate."
Researchers aboard the "Polarstern" worked among Arctic sea ice - which is melting due to climate change
From sea ice to the dinner plate
Sea ice is not only a trap or sink, but also a "transport vehicle" for microplastics, Ilka Peeken, a biologist at AWI and co-author of the report, told DW.
As melting sea ice drifts into warmer parts of the Atlantic, for example, it leaves a trail of microplastic that clings to algae and ends up in deep sea sediments on the ocean floor. Most worryingly, much is then rapidly absorbed into the food web.
Though microplastics might be toxic in themselves, an added concern is their ability to absorb hazardous chemicals from the water and surrounding environment.
"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," said Peeken.
Scientists are still unsure of the effect of microplastics ingested by such organisms and transported up the food chain. While some creatures can ingest this plastic debris without any known ill-effects, mussels, for example, can suffer inflammation.
But the fact that mussels, like oysters and other shellfish, are ingesting microplastics before they end up on dinner plates could have a potentially toxic effect on humans. "There might be implications for human health," said Peeken.
Research conducted in 2017 for Sky Ocean Rescue argued that "seafood eaters are absorbing tiny pieces of plastic into their bloodstream with unknown effects on their health."
While scientists believe that more than 99 percent of the microplastics pass through the human body, the 1 percent remains in body tissue and could raise toxicity levels over time.
From far and wide
Having gathered the ice samples over the course of three expeditions to the Arctic Ocean in the spring of 2014 and summer of 2015, the AWI research team noted that particle density and composition varied significantly among the samples. This hints at the diverse sources of the plastic pollutant.
Ice floes pushed along the Bering Strait and into the Arctic Ocean contained particularly high concentrations of polyethylene particles that are mostly found in packaging, meaning the so-called Great Pacific Garbage Patch is a likely source.
"These findings suggest that the expanding shipping and fishing activities in the Arctic are leaving their mark," said Peekan. "So, we have large impacts from urban areas, and also localized pollution."
In addition to packaging materials like polyethylene and polypropylene, the researchers found a total of 17 different types of plastic in the sea ice, including polyester and cellulose acetate, which is used primarily to make cigarette filters.
Despite research on microplastics in sea ice being in an early stage, the implications of this study are significant.
"Although we still have a lot to learn about the effects of microplastics," said Chelsea Rochman, "there is enough evidence for concern, especially in such a vulnerable and remote ecosystem."