Data from: Resistance of corals and coralline algae to ocean acidification: physiological control of calcification under natural pH variability

Ocean acidification is a threat to the continued accretion of coral reefs,
though some undergo daily fluctuations in pH exceeding declines predicted
by 2100. We test whether exposure to greater pH variability enhances
resistance to ocean acidification for the coral Goniopora sp. and
coralline alga Hydrolithon reinboldii from two sites: one with low pH
variability (< 0.15 units daily; Shell Island), and a site with
high pH variability (up to 1.4 pH units daily; Tallon Island). We grew
populations of both species for >100 days under a combination of
differing pH variability (high/low) and means (ambient pH 8.05/ocean
acidification pH 7.65). Calcification rates of Goniopora sp. were
unaffected by the examined variables. Calcification rates of H. reinboldii
were significantly faster in Tallon than Shell Island individuals, and
Tallon Island individuals calcified faster in the high variability pH 8.05
treatment compared to all others. Geochemical proxies for carbonate
chemistry within the calcifying fluid (cf) of both species indicated that
only mean seawater pH influenced pHcf. pH treatments had no effect on
proxies for Ωcf. These limited responses to extreme pH treatments
demonstrates some calcifying taxa may be capable of maintaining constant
rates of calcification under ocean acidification by actively modifying
Ωcf.