European sea bass, Dicentrarchus labrax, in a changing ocean

Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered to be a major global threat to marine ecosystems. To investigate the potential effects of ocean acidification on the early life stages of a commercially important fish species, European sea bass (Dicentrarchus labrax), 12 000 larvae were incubated from hatch through metamorphosis under a matrix of two temperatures (17 and 19 degrees C) and two seawater pCO(2) levels (ambient and 1,000 mu atm) and sampled regularly for 42 days. Calculated daily mortality was significantly affected by both temperature and pCO(2), with both increased temperature and elevated pCO(2) associated with lower daily mortality and a significant interaction between these two factors. There was no significant pCO(2) effect noted on larval morphology during this period but larvae raised at 19 degrees C possessed significantly larger eyes and lower carbon: nitrogen ratios at the end of the study compared to those raised under 17 degrees C. Similarly, when the incubation was continued to post-metamorphic (juvenile) animals (day 67-69), fish raised under a combination of 19 degrees C and 1000 mu atm pCO(2) were significantly heavier. However, juvenile D. labrax raised under this combination of 19 degrees C and 1000 mu atm pCO(2) also exhibited lower aerobic scopes than those incubated at 19 degrees C and ambient pCO(2). Most studies investigating the effects of near-future oceanic conditions on the early life stages of marine fish have used incubations of relatively short durations and suggested that these animals are resilient to ocean acidification. Whilst the increased survival and growth observed in this study supports this view, we conclude that more work is required to investigate whether the differences in juvenile physiology observed in this study manifest as negative impacts in adult fish.