Physiological plasticity and local adaptation to elevated pCO 2 in calcareous algae: an ontogenetic and geographic approach

To project how ocean acidification will impact biological communities in the future, it is critical to understand the potential for local adaptation and the physiological plasticity of marine organisms throughout their entire life cycle, as some stages may be more vulnerable than others. Coralline algae are ecosystem engineers that play significant functional roles in oceans worldwide and are considered vulnerable to ocean acidification. Using different stages of coralline algae, we tested the hypothesis that populations living in environments with higher environmental variability and exposed to higher levels of pCO 2 would be less affected by high pCO 2 than populations from a more stable environment experiencing lower levels of pCO 2. Our results show that spores are less sensitive to elevated pCO 2 than adults. Spore growth and mortality were not affected by pCO 2 level; however, elevated pCO 2 negatively impacted the physiology and growth rates of adults, with stronger effects in populations that experienced both lower levels of pCO 2 and lower variability in carbonate chemistry, suggesting local adaptation. Differences in physiological plasticity and the potential for adaptation could have important implications for the ecological and evolutionary responses of coralline algae to future environmental changes.