The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation

The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris.

The article

Mounting litter spotted on Arctic seafloor

Litter isn’t only a problem on land—it’s also found deep in the ocean. Despite an international treaty banning waste disposal at sea, trash from illegal dumping, commercial fishing, and maritime accidents has accumulated on the ocean floor. Now scientists have analyzed thousands of photographs of a swath of the bottom of the Arctic Ocean taken between 2002 and 2014 and calculated changes in marine litter over time. The results are troubling: The litter has become 4 times denser since 2004, and in one place its density has shot up 23-fold.

By Katherine Kornei, EOS, 98, 16 February 2017

The news

Marine litter on deep Arctic seafloor continues to increase and spreads to the North at the HAUSGARTEN observatory

The increased global production of plastics has been mirrored by greater accumulations of plastic litter in marine environments worldwide. Global plastic litter estimates based on field observations account only for 1% of the total volumes of plastic assumed to enter the marine ecosystem from land, raising again the question ‘Where is all the plastic? ’. Scant information exists on temporal trends on litter transport and litter accumulation on the deep seafloor. Here, we present the results of photographic time-series surveys indicating a strong increase in marine litter over the period of 2002–2014 at two stations of the HAUSGARTEN observatory in the Arctic (2500 m depth).

Plastic accounted for the highest proportion (47%) of litter recorded at HAUSGARTEN for the whole study period. When the most southern station was considered separately, the proportion of plastic items was even higher (65%). Increasing quantities of small plastics raise concerns about fragmentation and future microplastic contamination. Analysis of litter types and sizes indicate temporal and spatial differences in the transport pathways to the deep sea for different categories of litter. Litter densities were positively correlated with the counts of ship entering harbour at Longyearbyen, the number of active fishing vessels and extent of summer sea ice. Sea ice may act as a transport vehicle for entrained litter, being released during periods of melting. The receding sea ice coverage associated with global change has opened hitherto largely inaccessible environments to humans and the impacts of tourism, industrial activities including shipping and fisheries, all of which are potential sources of marine litter.

Mine B. Tekman, Thomas Krumpen, Melanie Bergmann,  Deep Sea Research Part I: Oceanographic Research Papers, Volume 120, February 2017, Pages 88–99

The article

Microplastic pollution in the Greenland Sea: Background levels and selective contamination of planktivorous diving seabirds

Microplastics have been reported everywhere around the globe. With very limited human activities, the Arctic is distant from major sources of microplastics. However, microplastic ingestions have been found in several Arctic marine predators, confirming their presence in this region. Nonetheless, existing information for this area remains scarce, thus there is an urgent need to quantify the contamination of Arctic marine waters. In this context, we studied microplastic abundance and composition within the zooplankton community off East Greenland. For the same area, we concurrently evaluated microplastic contamination of little auks (Alle alle), an Arctic seabird feeding on zooplankton while diving between 0 and 50 m. The study took place off East Greenland in July 2005 and 2014, under strongly contrasted sea-ice conditions. Among all samples, 97.2% of the debris found were filaments. Despite the remoteness of our study area, microplastic abundances were comparable to those of other oceans, with 0.99 ± 0.62 m−3 in the presence of sea-ice (2005), and 2.38 ± 1.11 m−3 in the nearby absence of sea-ice (2014). Microplastic rise between 2005 and 2014 might be linked to an increase in plastic production worldwide or to lower sea-ice extents in 2014, as sea-ice can represent a sink for microplastic particles, which are subsequently released to the water column upon melting. Crucially, all birds had eaten plastic filaments, and they collected high levels of microplastics compared to background levels with 9.99 and 8.99 pieces per chick meal in 2005 and 2014, respectively. Importantly, we also demonstrated that little auks took more often light colored microplastics, rather than darker ones, strongly suggesting an active contamination with birds mistaking microplastics for their natural prey. Overall, our study stresses the great vulnerability of Arctic marine species to microplastic pollution in a warming Arctic, where sea-ice melting is expected to release vast volumes of trapped debris.

F. Amélineau, D. Bonnet, O. Heitz, V. Mortreux, A.M.A. Harding, N. Karnovsky, W. Walkusz, J. Fort, D. Grémillet, Environmental Pollution, Volume 219, December 2016, Pages 1131–1139

The article

Observations of floating anthropogenic litter in the Barents Sea and Fram Strait, Arctic

Although recent reports indicate that anthropogenic waste has made it to the remotest parts of our oceans, there is still only limited information about its spread, especially in polar seas. Here, we present litter densities recorded during ship- and helicopter-based observer surveys in the Barents Sea and Fram Strait (Arctic). Thirty-one items were recorded in total, 23 from helicopter and eight from research vessel transects. Litter quantities ranged between 0 and 0.216 items km−1 with a mean of 0.001 (±SEM 0.005) items km−1. All of the floating objects observed were plastic items. Litter densities were slightly higher in the Fram Strait (0.006 items km−1) compared with the Barents Sea (0.004 items km−1). More litter was recorded during helicopter-based surveys than during ship-based surveys (0.006 and 0.004 items km−1, respectively). When comparing with the few available data with the same unit (items km−1 transect), the densities found herein are slightly higher than those from Antarctica but substantially lower than those from temperate waters. However, since anthropogenic activities in the Fram Strait are expanding because of sea ice shrinkage, and since currents from the North Atlantic carry a continuous supply of litter to the north, this problem is likely to worsen in years to come unless serious mitigating actions are taken to reduce the amounts of litter entering the oceans.

Melanie Bergmann, Nadja Sandhop, Ingo Schewe, Diederik D’Hert, Short Note, Polar Biology, Volume 39, Issue 3, pp 553-560, March 2016

The article

 

 

New IUCN research project : Microplastics: A global disaster in the Arctic Ocean

Microplastics pollution in the Arctic and its effects on ecosystems, human health and ice formation and melting are the subject of a newly launched IUCN research project.

The pioneering project aims to assess the origins of microplastics and the effects of plastic ingestion on marine life as well as food safety consequences for humans. It will also analyse the physical and chemical impacts of microplastic presence in Arctic sea ice, including how it may affect formation and melting of ice. With this information in hand, IUCN will provide recommendations to governments, industries, local communities and civil society to design mitigation solutions. (…)

IUCN, 26/01/2016

 

Microplastics in Arctic polar waters: the first reported values of particles in surface and sub-surface samples

Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16 cm) and sub-surface (6 m depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment.

 

Amy L. Lusher, Valentina Tirelli, Ian O’Connor, Rick Officer, Scientific Reports 5, 14947, October 2015

 

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