Increased adrenal responsiveness and delayed hatching date in relation to polychlorinated biphenyl exposure in Arctic-breeding black-legged kittiwakes (Rissa tridactyla)

High levels of environmental contaminants such as polychlorinated biphenyls (PCBs), organochlorine
pesticides (OCPs) and mercury (Hg) have been reported in some Arctic top predators such as seabirds.
Chronic exposure to these contaminants might alter the response to environmental changes through
interference with the regulation of corticosterone (CORT), a glucocorticoid stress hormone released by
the hypothalamo–pituitary–adrenal (HPA) axis. Positive and negative relationships between CORT and
environmental contaminants have been reported in polar seabirds. However, patterns appear
inconclusive and it is difficult to attribute these relationships to a dysfunction of the HPA axis or to other
confounding effects. In order to explore the relationships between the HPA axis activity and contaminants,
we tested whether different aspects of the HPA axis of an Arctic seabird, the black-legged kittiwakes
Rissa tridactyla, would be related to blood Hg, PCB and OCP concentrations. Male kittiwakes
were caught during the incubation period in Svalbard and were subjected to different stress series: (1)
a capture-restraint stress protocol, (2) an injection of dexamethasone (DEX) that enabled to test the
efficacy of the HPA negative feedback and (3) an injection of adrenocorticotropic hormone (ACTH) that
informed on the adrenal responsiveness. The HPA axis activity was unrelated to ROCPs and Hg.
However, birds with high concentrations of RPCBs released more CORT after the ACTH injection. It is
suggested that RPCBs may increase the number of ACTH-receptors on the adrenals. Additionally,
hatching date was delayed in males with higher concentrations of RPCBs and ROCPs. This study gives
new evidence that PCBs and adrenal activity may be related. Thus high PCB burden may make individuals
more prone to other stressors such as ongoing climate change.
Corticosterone
ACTH
Dexamethasone
Adrenal gland
PCBs
Reproduction