Meeting Abstract

40-2  Friday, Jan. 6 08:15 – 08:30  Factorial manipulation of CO₂ and temperature on algal-herbivore pair demonstrates that changes in herbivore population size will drive species interaction not per capita effects. ANDERSON, KM*; HELDT, KA; MUNGIA, P; RUSSELL, B; HARLEY, CDG; CONNELL, SD; University of British Columbia; University of Adelaide; University of Adelaide; Hong Kong University; University of British Columbia; University of Adelaide kat@zoology.ubc.ca https://nereocystis.wordpress.com/

Herbivores have the potential to maintain biodiversity and regulate primary productivity. Such interactions are potentially greatly affected by changes in individual metabolism and population size. Similarly, changes in primary producer palatability may mediate the top down pressure exerted by herbivore populations. There is reason to expect either or both of these processes to be affected by increases in ocean temperature and/or carbon dioxide associated with climate change. Using a mesocosm experiment spanning several generations of amphipod populations, we established that a strong interaction between elevated CO₂ and temperature drove a near doubling in overall herbivory. This increase in herbivory resulted from an increase in population size and biomass, despite evidence that per capita herbivore pressure will likely remain unchanged. It turns out that while temperature has a negative impact on per capita herbivore feeding rates and CO₂ a negative impact on algal palatability, when both algae and herbivores are simultaneously exposed to project the effects level out. In this way the impacts of climate change on population size swamp minimal changes in per capita level interaction strength.