Meeting Abstract
Rocky intertidal populations are routinely subjected to receding tides coupled with increases in body temperatures, leading to fluctuating physiological demands and stress. This dynamic thermal variation is compounded by within-site variation in individuals’ body temperature. For example, data from our first field season have confirmed that in Mytilus californianus, the ribbed sea mussel, variation in body temperature among adjacent individuals can exceed 6ºC, a range comparable with between-bed and regional-scale mean differences. This micro-scale variation represents a potentially critical caveat to the conclusion that a number of species currently live close to their thermal tolerance limits; rather, only a subset of individuals within a species are likely to do so. We assessed mechanistic consequences of micro-scale variation in body temperature within this species by abolishing such variation and quantifying several aspects of their physiology. Individuals were assayed 1) directly from the field, 2) after common gardening in the laboratory for 1 month, and 3) after outplanting individuals back into the field after common gardening. We measured whole-organism metabolic rate; tissue catalase activity, glutathione reductase activity, and total antioxidant capacity; and reactive oxygen species (ROS) production in hemocytes. Some individuals were used for baseline correlations at the control temperature (13°C), and others were assayed following exposure to controlled thermal challenges. Here we correlate individuals’ body temperature and ROS production in hemocytes to physiological abilities to cope with oxidative stress associated with thermal extremes.
