How do we Measure the Environment? Linking Intertidal Thermal Physiology and Ecology Through Biophysics

Recent advances in quantifying biochemical and cellular-level responses to thermal stress have facilitated a new exploration of the role of climate and climate change in driving intertidal community and population ecology. To fruitfully connect these disciplines, we first need to understand what the body temperatures of intertidal organisms are under field conditions, and how they change in space and time. Newly available data logger technology makes such an exploration possible, but several potential pitfalls must be avoided. Body temperature during aerial exposure is driven by multiple, interacting climatic factors, and extremes during low tide far exceed those during submersion. Moreover, because of effects of body size and morphology, two organisms exposed to identical climatic conditions can display very different body temperatures, which can also be substantially different from the temperature of the surrounding air. These same factors drive the temperature recorded by data loggers, and one logger type is unlikely to serve as an effective proxy for all organisms at a site. Here I describe the difficulties involved in quantifying patterns of body temperature in intertidal organisms, and explore the implications of this complexity for intertidal physiological ecology. I do so using data from temperature loggers designed to mimic the thermal characteristics of the mussel Mytilus californianus, and deployed at multiple sites along the West Coast of the United States. Results indicate a highly intricate pattern of thermal stress, where the interaction of climate with the dynamics of the tidal cycle determines the timing and magnitude of temperature extremes, creating a unique "thermal signal" at each site.