Combined effects of elevated pCO2, temperature, and starvation stress on larvae of a large tropical marine fish

Ocean acidification and other environmental changes pose an ecological challenge to marine organisms globally. Although the youngest life stages of these organism are likely to be most affected, a limited number of studies of larval fishes have investigated the effects of combined stressors. We conducted two experiments on larval cobia (Rachycentron canadum) raised under combinations of elevated pCO(2) and increased temperature or starvation stress. Larvae responded to individual CO2, temperature, and rationing treatments, and there was a negative effect of elevated pCO(2) on starvation resistance, but few synergistic effects of combined stressors. Elevated pCO(2) (1700-2100 mu atm pCO(2)) caused a transient but significant reduction in larval standard length (SL), growth rate, and development rate, while warmer temperature (32 vs. 27 degrees C) caused a consistent increase in SL, development rate, and swimming ability. Larval condition (RNA: DNA ratio) was unaffected by elevated pCO(2) although larvae fed a 25% ration had significantly reduced SL, growth rate, and development rate. Under complete feeding cessation, larvae in elevated-pCO(2) seawater demonstrated lower starvation resistance, indicating that acidification may increase starvation risk in a patchy marine environment. Overall, our results indicate that larval cobia are resistant to any major direct impact of combined elevated pCO(2) and temperature or rationing stress.