Meeting Abstract

S1-1.4  Jan. 4  If at first you don’t set seed, dry, dry, again CARRINGTON, E.; University of Washington ecarring@u.washington.edu

Rocky intertidal shores are often dominated by macroalgae which are alternately subjected to submersion in seawater and emersion in air. While many terrestrial angiosperm populations endure prolonged arid conditions by producing seeds, intertidal macroalgae such as Mastocarpus papillatus, instead have physiological adaptations to tolerate repeated desiccation. However, photosynthesis requires tissue hydration and thus desiccation potentially comes at the expense of reduced primary productivity. As with the broad leaves of Vogel (1970), morphology can influence the rate of mass (water vapor) and heat convection between a thallus and its surrounding environment, thereby influencing thallus desiccation and temperature during emersion. This study evaluates the influence of thallus morphology on the growth and persistence of an intertidal macroalga. A synthetic model was developed from previous analyses of the environmental physiology and heat budget of the red alga M. papillatus, using local meteorological conditions to provide a continuous estimate of thallus temperature, desiccation, and productivity. Run over an entire year, the simulations suggest that emersed carbon fixation is not an important component of the total carbon budget of a thallus, and that productivity is largely determined by the duration of daytime high tides. Changes in thallus morphology (e.g., thickness, branching) have only subtle effects on productivity, but dramatic effects on whether lethal temperatures are encountered during emersion. This synthetic approach not only provides a useful tool to evaluate potential trade-offs in performance with morphology, but also allows for prediction of the consequences of climate change on the productivity and persistence of a common intertidal species.