The seafloor in the Arctic deep sea is becoming increasingly polluted with plastic garbage and waste, according to researchers. There is more trash seen at the AWI deep-sea observatory HAUSGARTEN in the Arctic than even in a deep-sea canyon that’s located next to Lisbon, Portugal.
The new research was led by Dr. Melanie Bergmann, a biologist and deep-sea expert at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.
For this research, Dr. Melanie Bergmann analyzed around 2100 photos of the seafloor that were taken near HAUSGARTEN, the deep-sea observatory of the Alfred Wegener Institute in the eastern Fram Strait. This area is currently used as the sea route between Greenland and the Norwegian island Spitsbergen. “The study was prompted by a gut feeling. When looking through our images I got the impression that plastic bags and other litter on the seafloor were seen more frequently in photos from 2011 than in those dating back to earlier years. For this reason I decided to go systematically through all photos from 2002, 2004, 2007, 2008 and 2011,” Melanie Bergmann explains.
“The deep-sea scientists from the HGF-MPG Group for Deep-Sea Ecology and Technology of the Alfred Wegener Institute regularly deploy their towed camera system OFOS (Ocean Floor Observation System) during Polarstern expeditions to the HAUSGARTEN. At the central HAUSGARTEN station it is towed at a water depth of 2500 metres, 1.5 metres above the sea bed, and takes a photograph every 30 seconds. Deep-sea biologists principally use these photographs to document changes in biodiversity with respect to larger inhabitants such as sea cucumbers, sea lilies, sponges, fish and shrimps.”
They can also show clear evidence of quickly increasing levels of deep-sea pollution. “Waste can be seen in around one percent of the images from 2002, primarily plastic. In the images from 2011 we made the same discovery on around two percent of the footage. The quantity of waste on the sea bed has therefore doubled,” the researcher says. “If we consider the time span between 2007 and 2011 the amount has even risen by an order of magnitude.”
Someone reading this might say that ‘two percent’ doesn’t sound like much, but it is really just the tip of the human-caused changes occurring in the Arctic and elsewhere. “The Arctic Ocean and especially its deep-sea areas have long been considered to be the most remote and secluded regions of our planet. Unfortunately, our results refute this notion at least for our observatory. The quantities observed were higher than those recorded from a deep-sea canyon not far from the industrialised Portuguese capital Lisbon,” Melanie Bergmann explains. “It is also important to bear in mind that, according to recent research, more plastic waste will accumulate in deep-sea canyons than in open slope environments such as HAUSGARTEN.”
It isn’t possible to really tell where the trash is coming from just by looking at photographs. But the researchers do think that the loss of Arctic sea ice may be playing a part in the increase. “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. 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,” Melanie Bergmann says. “Furthermore, litter counts made during annual clean-ups of the beaches of Spitsbergen have shown that the litter washed up there originates primarily from fisheries.”
The increasing levels of trash are starting to have a noticeable effect on the deep-sea floor flora and fauna. “Almost 70 percent of the plastic litter that we recorded had come into some kind of contact with deep-sea organisms. For example we found plastic bags entangled in sponges, sea anemones settling on pieces of plastic or rope, cardboard and a beer bottle colonised by sea lilies,” Melanie Bergmann says.
Suspension feeders, such as sponges, are generally injured when they come into contact with plastic. They usually lose some of their ability to absorb food; consequently growing slower, and reproducing less. Some research has shown that their breathing may also be impaired, and there are of course the effects caused by the chemicals involved.
“Other studies have also revealed that plastic bags that sink to the seafloor can alter the gas exchange processes in this area. The sediment below then becomes a low oxygen zone, in which only few organisms survive,” Melanie Bergmann says. On the other hand, other animals use the waste as hard substratum to settle on. “This allows colonisation by species that previously would have found hardly any suitable substratum. This means that the waste could change the deep-sea composition of species and therefore biodiversity in the long-term,” the researcher adds.
The researchers are now planning to expand their research: “Until now our results from the Fram Strait merely constitute a snapshot, reflecting the observations that we were able to make with the naked eye,” the scientist explains. As an example, they are planning to next explore the effects of ‘micro-plastic’ particles. “We took samples for the first time during the last expedition with our research ice breaker POLARSTERN to the HAUSGARTEN observatory. Our AWI colleagues from Helgoland will analyse them for micro-plastics.”
Micro-plastics are often ingested by marine animals, including many species of fish, and enter the human food chain that way.
“Pieces of plastic on the deep seafloor are unlikely to degrade into micro-plastics as quickly as is the case on the North Sea coast, for example. This is due to the lack both of sunlight at a depth below 200 metres and of strong water movement. Instead it is dark and cold there. Under these conditions plastic waste can probably persist for centuries.”
The research is being published in journal Marine Pollution Bulletin.
Source: Helmholtz Association of German Research Centres
Image Credits: Alfred Wegener Institute