Laboratory seawater studies are justified

In our view, your report 'Seawater studies come up short' (Nature 524, 18–19; 2015) fails to capture the nuances of the survey results you discuss (see C. E. Cornwall and C. L. Hurd ICES J. Mar. Sci. http://doi.org/68g; 2015).

Researchers aim to follow the 2010 'Guide to best practices for ocean acidification research and data reporting' (go.nature.com/sp5kgn) as they strive to understand how marine organisms are likely to respond to the falling pH of the world's oceans, caused by increased carbon dioxide concentrations. The logistical constraints of testing the effects of seawater acidification on marine life in the laboratory are considerable. However, experiments must be replicated while complying with the requirements for manipulating and monitoring seawater carbonate chemistry.

The paper, co-authored by two of us, does not conclude from its meta-analysis of such manipulation experiments that all these studies “come up short”. Rather, it uses them to highlight the importance and challenges of proper experimental design for such testing. The examples of experimental pitfalls it cites are intended not as criticisms, but to guide future efforts.

Together with palaeo-record investigations, modelling studies and natural and manipulated field experiments, we believe that laboratory experiments are crucial to the mechanistic understanding and prediction of ocean-acidification impacts.