Chlordane: a banned insecticide could accelerate ageing of Arctic seabirds

Persistent organic pollutants (POPs) are synthetically manufactured chemicals extensively used during the 20th century in numerous industrial, commercial and agricultural applications. Harmful for living organisms, POPs are in the spotlight of toxicological studies leading to past and on-going national and international restrictions/ regulations, well-illustrated by the Stockholm Convention adopted in 2001 to protect human health and environment. Despite overall temporal declining trends, the so-called “legacy POPs”, a group of organic contaminants prohibited for decades, are still present in high concentrations and highly toxic for wildlife.

Due to their high volatility and persistence, POPs reach remote areas such as the Arctic. Once deposited in the marine ecosystem, they are assimilated by living organisms with food intake. As long-lived top predators, seabirds are chronically exposed to a complex cocktail of toxic chemicals. Among them, chlordane, a banned insecticide extensively used during >35 years, has been suggested to be particularly toxic for Arctic seabirds, well exemplified by the reduced survival probability reported in the most contaminated birds.

We organized a field expedition in Svalbard during the reproduction period of black legged kittiwakes, an abundant Arctic seabird. We caught 40 birds when they were sitting on the nest using a noose attached to a long pole. This was easier to catch them since kittiwakes build their nest in cliff, several meters above the ground. For each bird, we performed a small blood sampling in order to determine their contaminant levels and to measure various health-related parameters.

A group of black-legged kittiwakes

How to assess bird health?

Telomeres are DNA-protein complexes located at the end chromosomes which play a critical role in maintaining the genomic integrity. Telomere length progressively shortens along life because of repeated cell divisions. This is a natural phenomenon called “ageing”. However, ageing process can be accelerated by a wide range of environmental stressors. As a result, telomere length is considered as a good indicator of health. So far, the effects of contaminant exposure on telomere length has been poorly addressed which make this study particularly relevant.

Our results showed that among several POPs, only concentrations of oxychlordane, a metabolic product derived of chlordane, were negatively associated with telomere length in females but not in males. This suggests that oxychlordane could induce telomere shortening in female kittiwakes and thus, enhancing the ageing process. Interestingly, a recent study conducted in elderly people from Helsinki corroborates our results since they reported negative association between oxychlordane with telomere length in women but not in men. Moreover, in glaucous gull from Svalbard (another seabird species highly contaminated) and in kittiwakes from the same colony, oxychlordane has been associated with lower survival rate, especially in females. Reproduction is an energy demanding stage and egg production represents a significant and important additional cost for females compared to males which could make them more sensitive to oxychlordane.

Because telomere length appears as a good predictor of survival and longevity, female kittiwakes’ sensitivity to oxychlordane could affect telomere length, explaining the previously reported lower survival rate in highly contaminated female kittiwakes.

This study has been realized during my PhD. This project was supported by the Institut Polaire Français, by the Agence Nationale de la Recherche (POLARTOP project led by O.Chastel/ CEBC) and by the Research Council of Norway (AVITOX project led by J.O. Bustnes/ NINA).

Reference:

Blévin, P., Angelier, F., Tartu, S., Ruault, S., Bustamante, P., Herzke, D., ... & Chastel, O. (2016). Exposure to oxychlordane is associated with shorter telomeres in arctic breeding kittiwakes. Science of the Total Environment, 563, 125-130.

For more information:

Goutte, A., Angelier, F., Welcker, J., Moe, B., Clément-Chastel, C., Gabrielsen, G. W., ... & Chastel, O. (2010). Long-term survival effect of corticosterone manipulation in black-legged kittiwakes. General and comparative endocrinology, 167(2), 246-251.

Photo credit: Pierre Blévin