Global climate change is exposing ecosystems to multiple environmental stressors, including altered thermal conditions, changing resource bases, and changes in pollutant cycling. Thus, a pressing research priority for ecologists and conservation biologists involves understanding how multiple stressor interactions will affect biological systems as climate change progresses. Of special note, increases in chemical contaminant exposure concurrent with climate change have the potential to affect organismal responses to other climate change-associated stressors, impairing resiliency. The Arctic marine biota is especially vulnerable to joint effects of climate change and environmental contamination, as the Arctic is warming >3 times as fast as other regions, leading to cascading ecological effects. Furthermore, anthropogenic emissions have led to accumulation of pollutants in the Arctic, and particularly to high levels of mercury (Hg) pollution. Some recent data suggest increasing Hg exposure in Arctic animals concurrent with climate change, raising the alarming possibility that climate change and increasing Hg exposure could have interactive effects on Arctic animals.
Ecotoxicological studies in the Arctic, and elsewhere, have not adequately considered how behavioural and physiological effects of Hg might impair animal resiliency to climate change. Thus, the central objective of this project (BehavToxArc) was to explore interactive effects of Hg contamination and climate change on Arctic animals from behavioural ecological and ecophysiological perspectives using a keystone Arctic seabird species, the little auk (Alle alle), as a model system. Specific aims were:
1) To determine whether Hg exposure affects the capacity for behavioural plasticity in response to changes in foraging landscapes associated with climate change by limiting time activity budgets and behavioural performance traits (e.g. dive length).
2) To determine whether Hg exposure is associated with changes in the adrenocortical stress response that might limit behavioural patterns.
3) To determine whether Hg exposure affects animal personality traits (neophobia) that are key to determining responses to multiple stressor landscapes.
The primary conclusion deriving from the project is that subtle toxicological effects of Hg have the potential to inhibit animal behavioural responses to climate change, especially in the rapidly changing Arctic. In particular, we found evidence that Hg contamination might affect little auk diving patterns, with implications for foraging efficiency given changes in prey distribution in warming oceans. Behavioural toxicological effects of Hg contamination might be even more pronounced in species feeding at higher trophic positions than little auks, due to higher bioaccumulation levels. Thus, our work calls for further work to evaluate the extent to which Hg exposure might limit animal behavioural responses to climate change across a diversity of species representing different foraging niches, and to assess downstream effects on population stability.
