Study documents rising amount of sea-bottom debris
There’s more direct evidence that plastic pollution is increasing rapidly in the remote Arctic Ocean, according to German scientists, who have tracking sea-bottom litter at two research stations since 2002. The Hausgarten deep-sea observatory network includes a total of 21 stations in the Fram Strait, between Greenland and Svalbard.
The Alfred Wegener Institute’s Mine Tekman, lead author of a new study published in the scientific journal Deep-Sea Research I, said the long-term monitoring confirms that the amount of plastic litter has increased rapidly in the past 15 years. Other scientists with the AWI have also documented evidence of a floating garbage patch starting to form in the Barents Sea region of the Arctic Ocean. Plastic has already been reported from stomachs of resident seabirds and Greenland sharks.
And in 2012, scientists with the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association also documented plastic waste in the same area, finding that 70 percent of the plastic litter they recorded “had come into some kind of contact with deep-sea organisms,” including “plastic bags entangled in sponges, sea anemones settling on pieces of plastic or rope, cardboard and a beer bottle colonized by sea lilies.”
AWI researcher Melanie Bergmann suspects climate change is part of the cause.
“The Arctic sea ice cover normally acts as a natural barrier, preventing wind blowing waste from land out onto the sea, and blocking the path of most ships. Ship traffic has increased enormously since the ice cover has been continuously shrinking and getting thinner,” she said. “We are now seeing three times the number of private yachts and up to 36 times more fishing vessels in the waters surrounding Spitsbergen compared to pre-2007 times.”
In the new study, the scientists scanned the ocean floor with towed cameras. When they extrapolated the amount of debris they found over a larger area, they concluded there are an average of 3,485 pieces of litter per square kilometre in the monitoring period (2002 to 2014).
There has been a clearly recognizable increase in the past few years: when the team calculated a contamination level of 4,959 pieces of litter per square kilometre for 2011 in an earlier study, they hoped it was a statistical outlier. But the levels have continued to rise since, reaching a new peak of 6,333 pieces of litter per square kilometre in 2014.
At the northernmost station, the amount of litter increased 20-fold between 2004 and 2014,” according to Tekman. According to the AWI press release on the study, the level of contamination is similar to one of the highest litter densities ever reported from the deep seafloor, in Cap de Creus Canyon off the eastern coast of the Iberian Peninsula.
Most common are plastic and glass, and since glass doesn’t drift much, they concluded that it’s from local sources, primarily increased ship traffic in the region. Some of the plastic litter is likely transported into the region via the Gulf Stream, but the researchers also think there is a relationship between litter density and the summertime expansion of sea ice.
“If we’re right, sea ice could entrain floating litter during ice formation. During warmer periods, the ice breaks up and is transported to the south into the Fram Strait with the Transpolar Drift, releasing entrained litter into the survey area when it melts,” said Bergmann, a co-author of the study. “To date we’ve assumed just the opposite, since we viewed the ice as a barrier to litter contamination.”
The researchers are also tracking how the plastic degrades. They found more small pieces in the newest study, which was somewhat surprising since in the deep sea there is no UV light to break down the plastic, and the low temperatures are not conducive to disintegration.