Mar. Ecol. Prog. Ser. 388, 235-242 (2009)

Increased atmospheric CO₂ concentrations may pose a greater threat to some species of fish than previously predicted because of the combined effects of ocean acidification and increased temperature.

Philip Munday at James Cook University and his colleagues tested the aerobic scope (resting and active O₂ consumption) of two species of Australian coral reef fishes, Ostorhinchus doederleini and O. cyanosoma, in waters that modeled 2100 projections for temperature and pH.

In both species, aerobic scope declined over 30% in both above-average temperatures (29 to 32^oC) and in acidified water (pH 7.8 and ~1000 ppm CO₂). Mortality rates increased dramatically above 33^oC.

Reduced aerobic capacity in tropical fish species will likely affect feeding, growth and reproduction, threatening the stability of fish populations. Compounded effects of increased temperature and increased pH on non-calcifying marine organisms had been largely unknown, but this study indicates that some fish populations could be at significant risk if carbon emissions continue at the current rate.