Pollutants in Arctic foxes in Svalbard (Vulpes lagopus )

Closeup of an Arctic fox during summer.
Photo: Tore Nordstad / Norwegian Polar Institute

In Svalbard, the Arctic fox is a top predator and carrion eater feeding on the terrestrial and marine food chains, thus being exposed to high pollutant levels. The pollutant levels in the Arctic fox may also be affected by climate change. The Arctic fox is the only terrestrial predator in Svalbard, and the population is abundant and comparatively stable. By contrast, the species is threatened by extinction in mainland Norway. The monitoring shows a considerable decline in fat-soluble organic pollutants that are regulated internationally.

What is being monitored?

POPs from liver in Arctic fox from Svalbard

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The figure shows levels of PCB-153, DDE and oxychlordane measured in the livers of young Arctic foxes from Svalbard in the period 1992-2013. The PCB levels in Arctic foxes from Svalbard were at a stable, high level from 1973-74 until the end of the 1990s, after which they declined by 8% per year. The levels of DDE and oxychlordane in Arctic foxes from Svalbard also show a declining trend (9-12% per year) since the end of the 1990s.

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The figure shows levels of hexachlorobenzene (HCB) and HCH (beta-hexachlorocyclohexane) measured in the livers of young Arctic foxes from Svalbard in the period 1992-2013, and the brominated flame retardant BDE-47 in the period 1997-2013. The levels of HCB had a declining non-significant trend of 3% per year, and HCH fell by 4% per year in the period 1997-2013. The levels of the brominated flame retardant PBDE-47 show a declining trend (9% per year) in Arctic foxes from Svalbard since the end of the 1990s.

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The figure shows levels of the perfluorinated compounds PFOS (perfluorooctanesulfonate), PFNA (perfluorononanoate) and PFUnDA (perfluoroundecanoate) measured in the livers of young Arctic foxes from Svalbard in the period 1997-2014. The annual decline for PFOS is 8%. PFNA shows no temporal trend, while PFUnDA has a rising, non-significant trend since 2003.  

Status and trend

The levels of most organic pollutants have declined over the past 10 years in Arctic foxes from Svalbard.

PCB levels measured in Arctic fox liver remained stable from 1973–74 until the end of the 1990s, and the figures have gone down since then.

There may be some uncertainty attached to comparing the levels of pollutants analysed in the 1970s and 1980s with later results because different analytical methods may have been employed. Moreover, there is no information on the age and body condition of the foxes used in the earliest studies.

The levels of several herbicides, including chlordanes, DDE and brominated flame retardants (PBDE), have dropped since the end of the 1990s. There may be uncertainty attached to comparing the levels of pollutants analysed in the 1970s and 1980s with later results because different analytical methods may have been employed. Moreover, there is no information on the age and body condition of the foxes used in the earliest studies.

Levels of PFOS in Arctic foxes have fallen since the end of the 1990s. PFNA shows no temporal trend, while PFUnDA has a rising, non-significant trend since 2003.  

A more detailed study investigated temporal trends of organic pollutants in Arctic foxes from Svalbard relative to eating habits and food availability. The pollutant concentration was analysed in the livers of 141 Arctic foxes collected between 1997 and 2013. Concentrations of PCBs, chlordanes, DDE and brominated flame retardants (PBDE) went down by 4–11 % per year, whereas no trends were found for hexachlorobenzene (HCB) and hexachlorocyclohexane (HCH).

The concentration of all the substances was higher in Arctic foxes with a marine diet (e.g. seal carcasses) compared with a more terrestrial diet (e.g. reindeer carcasses). Increasing reindeer mortality, leading to greater availability of reindeer carcasses as food for Arctic foxes, was related to lower HCB concentrations in Arctic foxes. This may suggest that the concentration of HCB in Arctic foxes is influenced by winters when there is a high mortality of Svalbard reindeer, in other words they eat food containing low concentrations of HCB. It was also found that the HCH concentration had a positive relationship with the cover of sea ice in the fjords, i.e. marine prey were more easily available.

Once the inter-year variability of eating habits and food availability was taken into account, concentrations of PCBs, chlordanes, DDE and brominated flame retardants (PBDE) fell by 4-11% per year, whereas no trends were found for hexachlorobenzene (HCB) and hexachlorocyclohexane (HCH). Levels of PFOS have fallen since 2009, PFUnDA rose by 4% per year and PFNA showed a rising, non-significant trend. 

Levels of PCBs and chlordanes are higher in Arctic foxes in Svalbard than those in Canada and Alaska. HCH levels, on the other hand, are higher in North America than in Svalbard, whereas DDE and HCB levels had no geographical trend. The geographical trends in Arctic foxes correspond to those found in polar bears and seals.

Compared with polar bears, Arctic foxes have approximately equally high levels of PCBs and chlorinated pesticides, whereas levels of perfluorinated compounds are considerably lower in Arctic foxes than in polar bears.

Causal factors

The main reason for the decline in levels of most of the so-called legacy organic pollutants in Arctic foxes is that their manufacture and use are regulated nationally and internationally.

Efforts to regulate PCBs and chlorinated herbicides began at the end of the 1970s and the international ban on the substances under the Stockholm Convention came into force in 2004. The main sources of releases of these substances have therefore stopped.

The reason they are still found in the environment is because they are stable, and can recirculate and be concentrated up the food chain.

The manufacture and use of newer pollutants such as BDE-47 and PFOS have been restricted in the last 15 years. They were included in the Stockholm Convention in 2009. Trends in the levels of PFNA and PFUnDA are probably linked to the manufacture and use of these substances and their precursors, which are currently not regulated.

Consequences

Temporal trends of pollutants in apex predators are not only influenced by discharge patterns and regulations, but also by variations in the presence of various prey, which, in turn, are influenced by rapid changes in the climate in the Arctic. As discussed above, climate-related changes in the diet and the availability of prey may affect the level of pollutants in Arctic foxes from Svalbard.

PCBs and chlorinated herbicides (particularly oxychlordane) make up the greater part of the pollutant burden in Arctic foxes. The levels in Arctic foxes are still high, and comparable with those in polar bears. In common with many other arctic animals, Arctic foxes have seasonal variations in their body condition. As summer approaches, they burn the body fat they have in winter as a natural adaptation from winter to summer conditions, and may repeatedly through the winter also lose body weight when they find insufficient food and must fall back on their fat reserves.

Periods of hunger and consumption of body fat are natural for the Arctic fox, but the process may be critical because pollutants stored in fatty tissue are released into the blood stream when the fat is consumed. The pollutants will then be available to be taken up in vital organs like the liver and brain.

The Arctic fox also has high levels of PCB metabolites. This is because the Arctic fox is very efficient at converting PCBs to more water-soluble variants. The purpose of such conversion processes is to convert contaminants into other compounds that are more easily dissolved in water, and can hence be excreted from the body. But, in the process, metabolites of PCBs are also produced, which remain in the body, and these compounds are actually more toxic than the original ones.

Very little is known about the effects the high levels of pollutants might have on, for example, a nursing fox and her cubs, or a fox that fails to find food and must fall back on its fat reserves in winter. Experimental studies have shown health effects in farm foxes and sledge dogs in Greenland that were exposed to lower levels of pollutants than those found in arctic foxes from Svalbard. It is therefore likely that the pollutant levels have negative effects on the health of Arctic foxes.

About the monitoring

The Arctic fox is uppermost in the food chain in Svalbard, both on land and in the marine ecosystem, thus putting it at risk of taking up pollutants. High levels of POPs have been found in several sets of samples, initially from 1973–74, most recently in 2012–13. In particular, high levels of oxychlordane and highly chlorinated PCBs, including PCB-153 and PCB-180, were found.

Mapping of pollutants in Arctic foxes in Alaska, Canada and Norway has shown that Arctic foxes from Svalbard have the highest levels of pollutants. Negative effects have been shown from the present levels of pollutants in farm foxes, which implies a threat to Arctic foxes in Svalbard. Monitoring is therefore necessary.

The overall pollutant burden on Arctic foxes may also be affected by climate change, which further reinforces the importance of monitoring levels of pollutants in Arctic foxes.

 

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring