First experiment: percent cumulative mortality in juvenile M. galloprovincialis (A) and C. gallina (B) throughout the experiment under natural (Nc) and acidified (Ac) conditions. Bars are for standard deviation (replicate tanks: n ¼ 3). Asterisks are for t-test significance: * ¼ p < 0.05; ** ¼ p < 0.01.