The Role of Mobility in Intertidal Invertebrates’ Responses to Thermal Stress

As climate change progresses, it is important to be able to predict how the effects of elevated temperatures are affected by the ability of ectotherms to seek shelter. Many studies on ectotherms have suggested that mobility is a vital characteristic to understand how species will react to warming. Highly mobile ectotherms are not often exposed to thermally stressful conditions because they can actively select temperatures that are thermally beneficial or benign. Slow-moving or sessile ectotherms, however, are not able to change habitats quickly enough to escape from thermal stress or even death. In order to measure how mobility affected how organisms cope with temperature, we quantified the body temperatures, environmental temperatures (using biomimetic models), and thermal limits using respirometry of eight intertidal ectotherms in four mobility classes: fast, intermediate, slow, and sessile. In addition, we also calculated thermal safety margins (TSMs) for each of our species. While we predicted that fast and intermediately mobile species would have lower thermal limits and narrower TSMs than slow and sessile animals, we found that faster organisms had lower thermal limits and narrower thermal safety margins than the other three mobility classes. Our findings indicate that there is an effect of mobility on how organisms cope with temperatures and lay the groundwork for understanding how communities may respond to climate change.