Complex effects of contaminants in seals
This thesis reveals that hormone and vitamin systems have complex and highly variable responses to contaminant exposure. The responses of hormone and vitamin systems depend on the contaminant exposure and these effects may be compensated. Annual moulting/fasting status further confuses the relationships between hormone, vitamin and contaminant levels in seals. Contaminant effects also differ between closely related species living in the same environment, like ringed and grey seals.

Contaminants transformed to toxic metabolites
Contaminants are biotransformed to metabolites which may be highly toxic. The results of Heli Routti’s thesis showed that toxic metabolites of contaminants are formed in ringed seals from the Baltic Sea and to a lesser extent in the seals from Svalbard. The metabolites may further affect thyroid hormone homeostasis in the highly contaminated ringed seals.

Shortcomings in current risk assessment
Risk assessment for contaminant effects in wildlife has previously been based on comparisons between contaminant levels in wildlife and threshold levels of effects obtained from experimental or semi-field studies. This method has not taken into account that species are different. They may have different capacity to biotransform contaminants to highly toxic metabolites or they may have different physiological responses to contaminants. Risk for contaminant effects in wildlife population has also been assessed by relating the concentration of environmental contaminants to for example hormone or vitamin changes. However, this method often ignores the natural variation of hormone and vitamin levels and the complexity of a these systems.

What should be considered when assessing the risk of contaminants
Based on the results of this thesis, several recommendations that could be applied on monitoring and assessing risk for contaminant effects are provided. Metabolites should be included in monitoring and risk assessment programs due to their high toxic potential. It should be noted that hormones and vitamins may have complex and highly variable responses to contaminant exposure. These relationships may be further confused by moulting/fasting status. Therefore, it is highly recommended that when using variables related to hormone and vitamin homeostasis to investigate, monitor or assess the risk of contaminant effects in seals, the life history status of the animal should be carefully taken into consideration.
 

Contact: Heli Routti (heli.routti@npolar.no)

More information: Biotransformation and endocrine disruptive effects of contaminants in ringed seals - implications for monitoring and risk assessment (Heli Routti PhD thesis, pdf, 2.67 MB)

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Ring seal coming to the surface (photo: Christian Lydersen, NPI)

In the field (photo: Jukka Ikonen)