Predicting the impact of ocean acidification on benthic biodiversity: What can animal physiology tell us?

For the past 200 years, the oceans have been absorbing carbon dioxide at an unprecidented rate. It is now evident that this ongoing process has already significantly altered seawater carbon chemistry at a global scale and will continue to do so for hundreds of years to come; a phenomenon termed “ocean acidification”. The challenge currently facing scientists is to predict the long term implications of ocean acidification for the diversity of marine organisms and for the ecosystem functions this diversity sustains. This challenge is all the more difficult considering that empirical data which specifically address the impact of ocean acidification on marine biodiversity are currently lacking. In the face of growing political and public pressure to provide answers, what predictions can be made and how reliable are the assumptions on which those predictions depend? Here we review the extent to which the few existing data, and understanding gained from previous physiological studies, can be used to make predictions for marine biodiversity. In doing so we also scrutinise some established paradigms concerning the impact of hypercapnia, resulting from seawater acidification, on marine organisms.