Comparing the thermal tipping point of the overwintering and summer Arctic Calanus copepods in response to copper pollution

One of the main threat for arctic species is ocean warming, the arctic ocean warming 4 times faster than the others, at a pace unprecedented over the last million years. Even more concerning are marine heatwaves, i.e. sudden peak in maximal temperatures, that can last several weeks and should increase in intensity, duration and frequency. Marine heatwaves could have direct and delayed effects on the survival of copepods that are already weakened after being exposed to the winter extreme conditions for months. Therefore, determining the thermal tolerance threshold beyond which the survival of overwintering copepods is impacted is primordial to project on their fate. Furthermore, species are increasingly exposed to pollutants from human activities such as copper from increasing shipping and aquaculture in the Arctic. It has been shown than copper exposure can have a synergestic effect with heatwaves resulting in lower survival of several polar copepod species. However, this has never been studied on the dominants Arctic copepods from the genus Calanus. To fill this gap, I will expose Calanus hyperboreus sampled over the winter and summer period to 7 temperatures and 2-3 copper concentrations. This will allow to determine the temperature tolerance threshold of overwintering copepods and to see if it is influenced by potential copper toxicity. I will then conduct the same experiment over the summer on well-fed copepods to see if the tolerance to multiple stressor is affected by overwintering condition. This will increase our understanding of multiple stressor impacts over the winter.