Acclimation to predicted ocean warming through developmental plasticity in a tropical reef fish

Determining the capacity of organisms to acclimate and adapt to increased temperatures is key to understand how populations and communities will respond to global warming. Although there is evidence that elevated water temperature affects metabolism, growth and condition of tropical marine fish, it is unknown whether they have the potential to acclimate, given adequate time. We reared the tropical reef fish Acanthochromis polyacanthus through its entire life cycle at present day and elevated (+1.5 and+3.0 degrees C) water temperatures to test its ability to thermally acclimate to ocean temperatures predicted to occur over the next 50-100 years. Fish reared at 3.0 degrees C greater than the present day average reduced their resting oxygen consumption (RMR) during summer compared with fish reared at present day temperatures and tested at the elevated temperature. The reduction in RMR of up to 69 mg O-2 kg-1 h-1 in acclimated fish could represent a significant benefit to daily energy expenditure. In contrast, there was no acclimation to summer temperatures exhibited by fish reared at 1.5 degrees C above present day temperatures. Fish acclimated to +3.0 degrees C were smaller and in poorer condition than fish reared at present day temperatures, suggesting that even with acclimation there will be significant consequences for future populations of tropical fishes caused by global warming.