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Ocean acidification is a pervasive stressor that could affect many marine organisms and cause profound ecological shifts. A variety of biological responses to ocean acidification have been measured across a range of taxa, but this information exists as case studies and has not been synthesized into meaningful comparisons amongst response variables and functional groups. We used meta-analytic techniques to explore the biological responses to ocean acidification, and found negative effects on survival, calcification, growth and reproduction. However, there was significant variation in the sensitivity of marine organisms. Calcifying organisms generally exhibited larger negative responses than noncalcifying organisms across numerous response variables, with the exception of crustaceans, which calcify but were not negatively affected. Calcification responses varied significantly amongst organisms using different mineral forms of calcium carbonate. Organisms using one of the more soluble forms of calcium carbonate (high-magnesium calcite) can be more resilient to ocean acidification than less soluble forms (calcite and aragonite). Additionally, there was variation in the sensitivities of different developmental stages, but this variation was dependent on the taxonomic group. Our analyses suggest that the biological effects of ocean acidification are generally large and negative, but the variation in sensitivity amongst organisms has important implications for ecosystem responses.

It has been proposed that crustaceans should be excluded from a comparison of biological responses to ocean acidification among organisms with different calcium carbonate (CaCO3 ) forms in their calcified structures. We re-analysed our data without crustaceans and found high variation in organismal responses within CaCO3 categories. We conclude that the CaCO3 polymorph alone does not predict sensitivity, and a consideration of functional differences among organisms is necessary for predicting variation in response to acidification.

It has been proposed that crustaceans should be excluded from a comparison of biological responses to ocean acidification among organisms with different calcium carbonate (CaCO3) forms in their calcified structures. We re-analysed our data without crustaceans and found high variation in organismal responses within CaCO3 categories. We conclude that the CaCO3 polymorph alone does not predict sensitivity, and a consideration of functional differences among organisms is necessary for predicting variation in response to acidification.