Abstract: Ocean pH is projected to decrease 0.3-0.4 units by 2100 with increasing atmospheric CO₂, yet the consequences of declining pH and rising pCO₂ for fishes remain poorly understood.  Blue-spotted rockcod, a medium-sized predatory coral reef fish, were exposed to 400μatm (control), 900μatm (projected end-of-century), or 1800μatm pCO₂.  Oxygen consumption rates at rest (ṀO_2Rest) and following maximal exercise (ṀO_2Max) as well as blood and tissue parameters indicative of metabolic and/or pH/ion balance stress were examined.  Immediately upon CO₂ exposure, fish decreased ṀO_2Rest, butafter 48h, ṀO_2Rest was ~40% lower than control, regardless of treatment.  After 7d exposure, ṀO_2Rest had increased but was still 14% (900μatm-exposed) and 28% (1800μatm-exposed) lower than control fish.  Significant patterns were not detected in ṀO_2Max or aerobic scope.  Rockcod are ambush predators living within the reef matrix; peak activity and feeding occur just after dawn and before dusk, whereas activity is minimal several hours before sunrise. CO₂ levels fluctuate diurnally on coral reefs, being lowest by day and highest at night, peaking just before dawn due to accumulated CO₂ from reef respiration.  Diurnal CO₂ fluctuations may play a role in signalling metabolism, but the physiological mechanisms involved are not well understood.  Data suggest that end-of-century CO₂ levels may not overtly impact the metabolic physiology of this species, possibly reflecting adaptation to natural CO₂ fluctuations of their microhabitat and their activity patterns.  Interactions between ocean acidification and predator-prey dynamics remain largely unexplored but will be pivotal to the continued health of coral reef ecosystems.

Biography: Jodie is originally from the USA where she completed honours, BSc, and MSc degrees in Biology and Marine Biology before moving to Vancouver, Canada to commence a PhD at the University of British Columbia. During her PhD, she investigated the evolution of enhanced oxygen uptake and delivery in fish, but she has also done extensive research on buoyancy, exercise, and oxygen and temperature stress.  After a post-doctoral fellowship in Hong Kong with Prof. David Randall, she joined the ARC Centre of Excellence for Coral Reef Studies as a Super Science Fellow and applies her broad research interests in conservation and ecological physiology.  Jodie’s research aims to understand how evolutionary pressures have shaped physiological systems and the degree to which adaptation and acclimation to natural and environmental perturbations, such as anthropogenic climate change, can occur. She also likes to learn about and drink wine!