P3.14 Friday, Jan. 6 Cardiac performance and metabolism of an intertidal limpet under conditions of emersion and immersion BJELDE, B.E.*; TODGHAM, A.E.; San Francisco State University; San Francisco State University email@example.com
Species distribution and abundance are changing in the face of increasing temperature; however the physiological mechanisms underlying these shifts are not clear. Intertidal animals provide an excellent study group to examine how organisms respond to environmental stressors under different habitat conditions as their environment fluctuates between terrestrial and aquatic conditions with each tidal cycle. We investigated the physiological response of the finger limpet, Lottia digitalis, to thermal stress when exposed to elevated temperatures in water (immersed) or in air (emersed). Using measurements of heart rate and metabolic rate, we were able to examine both sensitivity to increases in temperature as well as thermal tolerance thresholds of limpets in air and water. Thermal limits of heart function were determined by calculating the temperature which caused a drastic drop in heart rate (break temperature) while heating at a rate comparable to a low tide period. Heart rate and metabolic rate, estimated through measurements of O2 consumption, were also measured in both environments under acute plunging experiments from 15-40°C at 5°C intervals. Final break temperatures were significantly higher (3-5ºC) in emersed limpets than immersed. Oxygen consumption was higher and more variable under conditions of emersion compared to immersion where limpets decreased O2 consumption with increasing temperature. Comparisons of heart rate differences between ramping and plunging experiments suggest that thermal tolerance thresholds depend on heat shock protocol. Temperature logger data suggests that L. digitalis are currently living close to their tolerance limits and may not have the capacity to keep up with increasing climate change or increased frequency of extreme heat waves.