Meeting Abstract

52.5  Saturday, Jan. 5  Regional comparisons of the effects of summer and winter low tide conditions on photosynthetic recovery in a high intertidal alga ELSBERRY, L.A.*; BURNAFORD, J.L.; California State University, Fullerton; California State University, Fullerton

Because the timing of low tides varies among locations along the US west coast, populations of a species can experience different abiotic conditions in different regions. We studied populations of the high intertidal alga Endocladia muricata in Washington and southern California to determine how individuals responded to regional ambient low tide conditions. We collected individuals from the high and low edges of the alga’s tidal distribution in winter and summer and determined their ability to recover from one hour and four hour exposures to low tide conditions. Low tide treatments were fully factorial with two hydration levels and three temperatures (winter=10°C, 20°C, 30°C; summer=20°C, 30°C, 40°C). We compared post-emersion photosynthetic rates to pre-emersion rates to evaluate recovery. Completeness and rate of recovery differed between individuals collected at different tidal heights and was affected by low tide temperature, desiccation state, and the length of the low tide exposure. Individuals from the high edge of Endocladia’s tidal distribution recovered from low tide conditions more completely than low edge individuals. In both regions and seasons, recovery was slowed following four hour low tide exposure compared to one hour low tide exposure. Individuals in high temperature treatments frequently showed reduced recovery relative to individuals in low temperature treatments, although the interaction between hydration status and temperature varied among seasons and regions. Understanding geographic variation in the factors that affect individual photosynthetic recovery following low tide exposure may help us make predictions about the persistence of populations in the face of climate change.