The harbour seal (Phoca vitulina) is a top predator and lives mostly on fish. This puts it at risk for high levels of pollutants. The harbour seal is a coastal seal species which has one of the widest ranges of all the seals in Norwegian waters. It is found from temperate waters in the Atlantic and Pacific oceans to arctic regions. In Svalbard, harbour seals are Red Listed and totally protected.

Two harbour seals in Kongsfjorden. Photo: Geir Wing Gabrielsen / Norwegian Polar Institute

What is being monitored?


Persistent organic pollutants in harbour seals

Both HCB and HCH have declined in harbour seals from 1999 to 2009.
(Cite these data: Norwegian Polar Institute (2022). HCB and HCH levels in harbour seal. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://mosj.no/en/influence/pollution/pollution-common-seal.html)


Both PCB-153 and p,p’-DDE have greatly declined in harbour seals from 1999 to 2009.
(Cite these data: Norwegian Polar Institute (2022). PCB-153 and DDE levels in harbour seal. Environmental monitoring of Svalbard and Jan Mayen (MOSJ). URL: http://mosj.no/en/influence/pollution/pollution-common-seal.html)

Details on these data

Update intervalEvery 10th year
Executive organizationNorwegian Polar Institute
Contact personsHeli Routti

Method

Biopsy was used to take blubber from anaesthetised harbour seals.

The chemical analyses were performed by the Norwegian Institute for Air Research (NILU), Tromsø office, in both 1999 and 2009–10.

The samples are processed in the laboratory using a variety of methods to permit the analysis of several groups of pollutants. See Herzke et al. (2009) for the analysis of organic, fat-soluble chemical sprays and PCB:

  • The blubber was extracted with cyclohexane-aceton (1:3).
  • The samples were cleaned using Gel Permeation Chromatography (GPC) followed by a florisil column.
  • The sample is analysed by interlinked, high-resolution, gas chromatography (GC) and mass spectrometry (MS). Helium is used as the carrier gas in the machine.

The concentrations are calculated by quantifying internal standards with known concentration and comparing these with the response (chromatogram) from the samples.

Detection limits for the individual compounds are 3 times the noise level of the instrument. The uncertainty is around 20%. The detection limit in particular, but also the measurement uncertainty, has been improved in recent years. In all the time series, there will therefore be greater uncertainty attached to measurements earlier in the series. The laboratory is accredited for analyses of pollutants and regularly takes part in international intercalibration tests.

Quality

The analysis is quality assured using the methods described in the accreditation. To avoid contamination, sterile equipment is used in the laboratory. 2 blank samples and 1 standard reference sample are analysed for each 10th sample. The laboratory regularly takes part in international intercalibration tests. See Herzke et al. (2009) for more details on the method.

The material derives only from 4–8 year-old adult males. As few individuals have been sampled each year (4 in 2009–10 and 6 in 1999), some uncertainty is attached to the data.

Since the data are acquired every 10th year, the analysis will not provide information on the variation in pollutant concentrations from year to year. The possibility that such variations are not being detected must therefore be taken into account when analysing the time series. It will therefore take a long time to demonstrate changes in the time series, since it is difficult to determine whether the difference between two measurement points is a consequence of genuine change, or random variation.

Other metadata

All data are published in scientific articles (Routti et al., 2014; Wolkers et al., 2004)

Reference level and action level

Since PCB, DDT, HCB and HCH are anthropogenic pollutants that are not found in a natural state, the reference level for an unaffected state will be zero (the detection limit).

No maximum values have been set for the content of pollutants in harbour seals.

Status and trend

Monitoring of harbour seals shows that the concentrations of fat-soluble organic pollutants (PCB-153, DDT, HCB and HCH) have declined from 1999 to 2009–10. This is in accordance with the trends for these substances seen in arctic wildlife. It is also confirmation that their regulation has been successful.

The PCB-153 levels for 2009–10 are quite similar to the levels found in harbour seals from California and British Columbia. Stranded harbour seals from the north-western Atlantic had more than one hundred times higher levels than the Svalbard harbour seals. The geographical differences are in keeping with the use of PCB globally, in that the highest consumption is in Europe and on the east coast of North America, followed by the west coast of North America. The levels of p,p’-DDE and α-HCH in stranded harbour seals from the north-western Atlantic were ten to one hundred times higher than in Svalbard harbour seals, whereas HCB was only two to three times higher. This may imply that the global distribution of HCB is almost in balance with the persistent organic pollutants (Cullon et al., 2012; Greig et al., 2011; Shaw et al., 2005).

Comparison with other seal species in Svalbard shows that harbour seals from 2009-10 have the same levels of PCB-153, p,p’-DDE, α-HCH and HCB as ringed seals from 2004 (Wolkers et al., 2008).

This data set is small and has few individuals, which means that the results risk being exposed to randomness where deviations can have a significant effect on the overall analysis. Notwithstanding this, the pollutants measured have declined so much that a reduction is not in doubt.

Since the data are acquired every 10th year, the analysis will not provide information on the variation in pollutant concentrations from year to year. The possibility that such variations are not being detected must therefore be taken into account when analysing the time series. It will therefore take a long time to demonstrate changes in the time series, since it is difficult to determine whether the difference between two measurement points is a consequence of genuine change, or random variation.

Causal factors

The manufacture and use of these substances are regulated nationally and internationally. The principal source for the supply of these substances has therefore stopped.

These substances are still to be found in the environment because they are stable and can be recirculated in the food chain. In addition, they leak from secondary sources like soils, lakes and glaciers in the Arctic. It is uncertain how climate change and the melting of sea ice, glaciers and permafrost will affect the pollutants.

Consequences

The levels of pollutants in harbour seals are regarded as low and do not constitute a health threat. The harbour seal is also regarded as being comparatively efficient in metabolising (breaking down) pollutants like PCB, and these metabolites (the breakdown products) have potential to disturb the hormone balance in the body, especially the thyroid hormone system.

About the monitoring

It is important to map the pollutants in this Red Listed harbour seal population in Svalbard to be able to say something about the pollutant situation in this population.

Places and areas

Relations to other monitoring

Monitoring programme

  • None

International environmental agreements

  • None

Voluntary international cooperation

  • None

Related monitoring

  • None

Further reading

Links

Publications

  1. Routti, H., Lydersen, C., Hanssen, L., & Kovacs, K.M. (2014). Contaminant levels in the world’s northernmost harbor seals (Phoca vitulina). Marine Pollution Bulletin 87: 140–146. https://doi.org/10.1016/j.marpolbul.2014.08.001.
  2. Wolkers, H., Lydersen, C., & Kovacs, K.M. (2004). Accumulation and lactational transfer of PCBs and pesticides in harbor seals (Phoca vitulina) from Svalbard, Norway. Science of The Total Environment 319(1-3): 137–146. https://doi.org/10.1016/S0048-9697(03)00449-2.
  3. Wolkers, H., Krafft, B.A., van Bavel, B., Helgason, L.B., Lydersen, C., & Kovacs, K.M. (2008). Biomarker responses and decreasing contaminant levels in ringed seals (Pusa hispida) from Svalbard, Norway. Journal of Toxicology and Environmental Health, Part A 71(15): 1009–1018. https://doi.org/10.1080/15287390801907558