EARLY LIFE HISTORY TRAITS INFLUENCE THE EFFECTS OF OCEAN ACIDIFICATION ON THE BEHAVIOR AND PHYSIOLOGY OF JUVENILE ROCKFISHES

Early life history traits influence the effects of ocean acidification on the behavior and physiology of juvenile rockfishes in central California Hamilton William Fennie Master of Science in Marine Science California State University Monterey Bay, 2015 The rapid increase of anthropogenic carbon dioxide (CO2) emissions to the atmosphere is altering seawater chemistry at an alarming rate. Many studies have shown that elevated dissolved seawater CO2 concentrations and associated decreases in seawater pH (termed ocean acidification) will result in negative impacts on marine organisms that accrete calcium carbonate structures. Recent research has also suggested that ocean acidification has the potential to negatively affect marine fishes by modifying behaviors and physiological processes; however, some species appear to be resilient to projected future pH changes. In this thesis, I investigated the potential for ocean acidification to impair the behavior and physiology of six closely related species of nearshore rockfishes (Sebastes spp.) in central California and tested whether the susceptibility or tolerance of each species to elevated CO2 was associated with their early life history strategy. Two life history syndromes were selected based on the conditions larvae and juveniles experience: canopy recruiting and benthic recruiting rockfish (n=3 species of each syndrome). Canopy recruiting species inhabit shallower water and experience relatively low CO2 conditions during development, whereas benthic recruiting species inhabit deeper water and experience higher CO2 levels during development. Individuals from each of these 6 species were reared in 4 CO2 treatments (540 ppm, 820 ppm, 2100 ppm, and 3300 ppm) for 3 months. During that time, I examined the effect of elevated CO2 on a suite of behavioral and physiological responses: behavioral lateralization, escape time, critical swimming speed, aerobic scope, and growth rate. Metaanalysis techniques were used to synthesize results across multiple experiments and to permit comparisons of the responses of the canopy recruiting group and benthic recruiting group to ocean acidification. I found that benthic recruiting species appear resistant to CO2-mediated impairments, whereas canopy recruiting species experienced altered brain function via a reversal of behavioral lateralization in two species and increased escape time in all three species. Additionally, all three canopy recruiting species experienced decreased swimming endurance in elevated CO2. These findings indicate that kelp forest rockfishes have life history-specific responses to ocean acidification. Either early exposure to high CO2 water during development allows benthic recruiting species to acclimate to OA conditions, or the benthic recruiting group has previously adapted to these conditions. If juvenile canopy species cannot acclimate or adapt to future OA conditions, their behavioral and physiological impairments may translate into increased mortality, as has been found in settlement stages of tropical species, and recruitment of canopy species may decline as climate change progresses. The divergent responses of these two groups of rockfish may indicate future changes in the species composition of kelp forest rockfish assemblages.