Arctic Plastic Litter
Plastic does not easily decompose. That darn plastic bag can move many thousands of miles. The sea bed in the Arctic deep sea is increasingly strewn with litter and plastic waste as reported in the advance online publication of the scientific journal Marine Pollution Bulletin by Dr. Melanie Bergmann, biologist and deep-sea expert at the Alfred Wegener Institute (AWI) for Polar and Marine Research in the Helmholtz Association. The quantities of waste observed at the AWI deep-sea observatory HAUSGARTEN are even higher than those found in a deep-sea canyon near the Portuguese capital Lisbon.
Hausgarten is the deep-sea observatory of the Alfred Wegener Institute in the eastern Fram Strait. It consists of 16 stations covering water depths of between 1000 and 5500 meters. Since 1999 samples were taken annually at these stations every year during the summer months.
For this study Dr. Melanie Bergmann examined some 2100 seafloor photographs taken near Hausgarten. This is the sea route between Greenland and the Norwegian island Spitsbergen. This is not exactly a major transit or tourist area.
"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.
At the central Hausgarten station it is towed at a water depth of 2500 meters, 1.5 meters 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 the larger inhabitants such as sea cucumbers, sea lilies, sponges, fish and shrimps. However, for Melanie Bergmann they also provided evidence of increasing 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 scientist says.
At first sight, the two percent result may not cause much concern. However a comparison demonstrates the true extent of the pollution in the Arctic deep sea: "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.
Melanie Bergmann is unable to determine the origin of litter from photographs alone. However she suspects that the shrinking and thinning of the Arctic sea ice may play an important role as wellas increasing shipping traffic. 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.
When sponges or other suspension feeders come into contact with plastic, this may cause injuries to the surface of their body. The consequence: the inhabitants of the sea bed are able to absorb fewer food particles, grow more slowly as a result, and probably reproduce less often. Breathing could also be impaired. "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.
Belgian mammal and bird observers also counted 32 pieces of litter floating at the water surface. The probability of researchers finding more litter on the deep ocean floor is therefore great. Melanie Bergmann: "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 meters and of strong water movement. Instead it is dark and cold there. Under these conditions plastic waste can probably persist for centuries."
For further information see Arctic Plastic.
Litter image via AWI.