Physiological adaptations play a key role in biogeographic patterning. Understanding how variation in physiological tolerances structures species distributions is critical to predicting species shifts and community resilience in the face of climate change. As part of a series of “Integrated Marine Science” courses, students at the University of Maine explore how to measure the physiological tolerances of the blue mussel (Mytilus edulis) a foundational species whose presence often influences the diversity and productivity of temperate zone intertidal communities.
In previous research, Braby and Somero used a method known as impendance pneumography to measure how heart rate changes under acute stress among three species in the genus Mytilus and demonstrated that the patterns of distribution for these congeners is correlated with tolerance to temperature and salinity stress. Our students use the same approach to estimate variation in physiological tolerance to acute temperature stress among mussels sampled from populations of M. edulis north and south of Cape Cod, MA, USA. They specifically focus on the determination of the high critical temperature (Hcrit) or Arrhenius break temperature, which is the point where heart activity falls sharply with increasing temperature. The class results suggest that mussels from southern populations show higher tolerance to acute thermal stress when compared to their northern conspecifics. We will discuss some ramifications of their findings and how these research activities enhance our undergraduate curriculum in marine science and further students’ understanding of how climate change research is conducted.