Corals can benefit from Climate Change Effects

From Taxing Air (Carter et al)
is there such a thing as ocean acidification, and should we worry about it? 
No, the oceans have always been alkaline and will remain so, despite any minor decrease in alkalinity caused by the absorbtion of extra carbon dioxide 
Having noted that, an ocean becoming less alkaline is known as ocean acidification, even if that ocean will never turn to acid.

 Phys.Org reports on a new paper published late last year in the journal Proceedings of the Royal Society B: Biological Sciences.

Researchers from Northeastern University's Marine Science Center and the University of North Carolina at Chapel Hill have found that moderate ocean acidification and warming can actually enhance the growth rate of one reef-building coral species. Only under extreme acidification and thermal conditions did calcification decline.
Science Daily summarises:
New research explains how mod­erate increases in ocean acid­i­fi­ca­tion and tem­per­a­ture can enhance the growth rates of some reef-forming corals. Authors of a new report attribute the coral's pos­i­tive response to mod­er­ately ele­vated carbon dioxide to the fer­til­iza­tion of pho­to­syn­thesis within the coral's algal sym­bionts, which may pro­vide the coral with more energy for cal­ci­fi­ca­tion even though the sea­water is more acidic. 
The Paper: (link)

The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming



Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1–0.3 pH units and sea surface temperature to increase by 1–4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate—suggesting that ocean warming poses a more immediate threat than acidification for this important coral species.