Increasing amounts of plastic litter on the seafloor of the Arctic Ocean

October 24th, 2012 by Alfred Wegener Institute for Polar and Marine Research

Dr. Melanie Bergmann, biologist and deep-sea expert at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, has found that the amount of plastic litter on the Arctic sea floor has increased.

An image of a plastic bag on the Arctic seafloor taken by the Ocean Floor Observation System (OFOS) in the Hausgarten area in July 2012 (click image to expand - ©Alfred Wegener Institute)

Her findings are reported in the paper “Increase of litter at the Arctic deep-sea observatory Hausgarten” published in Marine Pollution Bulletin.

Dr. Bergmann examined seafloor photographs taken on the sea route between Greenland and Spitsbergen near the Hausgarten deep-sea observatory from 2002, 2004, 2007, 2008 and 2011.

She found that plastic bags and other litter on the seafloor were more frequent in photos from 2011 than in those dating back to earlier years.

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 (Ocean Floor Observation System or OFOS) during Polarstern expeditions to the Hausgarten.

At the central Hausgarten station, OFOS is towed at a water depth of 2500 metres, 1.5 metres above the sea bed, and takes a photograph every 30 seconds.

These photographs are used to document changes in biodiversity on the seafloor. Dr Melanie Bergmann used the photographs to provide evidence of increasing deep-sea pollution.

“Waste, primarily plastic, can be seen in around 1% of the images from 2002. In the images from 2011 we made the same discovery on around 2% of the footage,” Dr Bergmann said.

The quantities of waste observed at the AWI deep-sea observatory Hausgarten in the eastern Fram Strait, which is a remote region, are higher than those found in a deep-sea canyon near Lisbon, Portugal, which according to recent research is the type of environment that should accumulate more plastic litter.

Dr Bergmann suspects that the shrinking and thinning of the Arctic sea ice may play a role in the increased amount of litter.

“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,” Dr Bergmann said.

The litter collected from Spitsbergen beaches originates primarily from fishing vessels.

“Almost 70% of the plastic litter we recorded had come into contact with deep-sea organisms.”

“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,” Dr Bergman said.

An image of plastic waste on the Arctic seafloor taken by the Ocean Floor Observation System (OFOS) in the Hausgarten area in July 2012 (click image to expand - image ©Alfred Wegener Institute)

Plastic litter can injury sponges or other suspension feeders and cause them to absorb fewer food particles, grow more slowly, and probably reproduce less often.

Plastic also contains additives, which have various toxic effects.

Studies have revealed that plastic bags on the seafloor can inhabit gas exchange, and reduce the amount of oxygen available in the area.

Some animals will use the waste as hard substrate to settle on.

“This allows colonisation by species that would not have found suitable substrate otherwise. Plastic waste could change the deep-sea composition of species and therefore the biodiversity in the long-term,” Dr Bergmann said.

“Our results from the Fram Strait constitute only a snapshot, reflecting the observations that we were able to make,” she said.

Dr Bergmann and colleagues want to expand their research projects on “litter in the sea” in view of the rapidly changing climate in the Arctic.

The focus of research is currently moving to the study of deep-sea micro-plastic particle pollution.

“We took samples during the last expedition with our research ice breaker R/V Polarstern. These samples will be analysed by AWI colleagues from Helgoland,” Dr Bergmann said.

Micro-plastics can be ingested by marine animals including commercially harvested prawns and fish, and enter the human food chain.

“Pieces of plastic on the deep seafloor are unlikely to degrade into micro-plastics as quickly as plastic on the North Sea coast,” Dr Bergmann said.

“Under these dark and cold conditions, plastic waste can probably persist for centuries,” she said.


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