Pollutants in ringed seals (Pusa hispida)

A ringed seal laying on snow-covered ice.
Photo: Bjørn Frantzen / Norwegian Polar Institute

Moderate levels of contaminants are found in ringed seals from Svalbard. Ringed seals are the polar bear's main prey, and moderate pollutant levels in ringed seals may contribute to high levels in polar bears. Most of the so-called old pollutants are decreasing in ringed seal, while a similar decrease has not been proven for newer contaminants.

What is being monitored?

POPs in ringed seals

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The figure shows a sharp reduction of PCB 153, DDE and chlordane (sum of transnonachlor and oxychlordan) levels measured in ringed seal blubber in the period 1992-2014. Annual decrease is 6-8%.

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The levels of hexachlorobenzene (HCB), alpha-hexachlorocyclohexane (HCH) and toxaphenes (sum of congeners 26 and 50) in ringed seal from Svalbard show a decline in the period 1992-2014. Annual decline is 6-11%. The levels of the brominated flame retardant BDE-47 shows no trend in ringed seals from Svalbard.

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The figure shows no significant trend of PFOS measured in the plasma of ringed seals over the period 1990-2010. Highest levels were measured in 2004, and in 2010 levels were halved.

Status and trend

Monitoring of ringed seals show that concentrations of fat-soluble organic pollutants (PCB-153, DDE, chlordanes) decreased 6.8 percent per year between 1992 and 2014. This is consistent with the trends seen in other arctic animals, and is a confirmation that international regulation of these pollutants have been successful.

The levels of HCB, α-HCH and toxaphenes in ringed seals from Svalbard also shows a decline in this period. The annual decline has been between 6 and 11 percent.

For the newer POPs, the situation is different. The levels of the brominated flame retardant PBDE-47 show no declining trend in ringed seals from Svalbard from 2004 to 2014, while the levels of PFOS have varied over the period 1990 to 2010, and show no significant trend. The highest PFOS concentrations were measured in 2004, and in 2010 the levels were halved.

Studies from Canada and Greenland show the same as in Svalbard. The old legacy pollutants such as PCBs, DDT, chlordanes and α-HCH decrease in concentration. The studies from Canada, which generally has been going on longer and contains more data than the studies of Svalbard, show that ringed seals today contain significantly less PCB and DDT than they did in the 1970s. At the same time, there are varying trends for the newer environmental toxicants such as brominated flame retardants and perfluoroalkyl and polyfluoroalkyl substances.

A study from 2007 showed that levels of PCBs, brominated flame retardants and pesticides in ringed seals livers is 6-15 times higher in the Baltic Sea than in Svalbard.

Current levels of PCBs, chlorinated pesticides and PFOS in ringed seals are low relative to polar bears.

Causal factors

The main reason why the levels of most of the legacy organic pollutants are decreasing in ringed seals, is that the production and use of them is regulated nationally and internationally.
Efforts to regulate PCBs and chlorinated pesticides started in the late 1970s, and the international ban on the contaminants took effect in 2004, through the Stockholm Convention. The main sources of emissions of these contaminants has therefore stalled.

The reason for the contaminants still being present in the environment is because they are stable and that they can be recycled and concentrated in the food chain.

Production and use of the newer POPs PBDE-47 and PFOS have been restricted in the past years. The largest manufacturer of PFOS, 3M, voluntarily stopped production of PFOS and related substances in the early 2000s. Both the brominated flame retardant PBDE-47 and PFOS were included in the Stockholm Convention in 2009.

Arctic cod is an important prey species for ringed seals, and ringed seals may be influenced by the level of contaminants in polar cod. As mentioned above, the level of contaminants in ringed seals affect the level of pollutants in polar bears, as they are a prey species for polar bears.

Consequences

Ringed seals from Svalbard have moderate levels of contaminants in their tissues. The levels of PCBs, pesticides and brominated flame retardants is considerably lower in ringed seals from Svalbard than in ringed seals from the Baltic Sea.


Recent studies show that the limits for when immune and endocrine effects may occur are very low in ringed seals. Therefore, there is reason to believe that the concentrations of the contaminants found in ringed seals on Svalbard can affect the immune- and hormonesystem of ringed seals on Svalbard at the molecular level.


Ringed seals can be particularly vulnerable to contaminants when they lose weight during molting. Periods of reductions in body fat allow pollutants stored in their blubber to be released into the blood. Contaminants are then available and taken up in important organs such as the liver and brain.

 

About the monitoring

The ringed seal is a small species of true seal that is found throughout the Arctic. It is the only seal in Norwegian waters that is capable of keeping breathing holes open in solid ice. In Svalbard, ringed seals have their pups on the ice in the fjords and in the pack ice in the Barents Sea.

The ringed seal is a key species in the plankton – polar cod – ringed seal – polar bear food chain. Ringed seals are monitored to understand how pollutants become concentrated up the food chain.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring
Other