Background
The authors write that "increasing dissolution of anthropogenic-released carbon dioxide into the world's oceans is causing ocean acidification (OA)," which they say "is thought to negatively affect most marine-calcifying organisms, notably cold-water corals (CWC)," which might be expected to be especially sensitive to OA, due to the deep and cold waters in which they are typically found.

What was done
In March of 2010 and February and March of 2011, Jantzen et al. measured water profiles with a CTD multi-probe (conductivity, temperature, depth) profiler (plus an oxygen probe in 2010 only) along the course of the Comau fjord, extending down to 50-60 meters in 2010 and down to 225 meters in 2011, while also collecting water samples using Niskin bottles. And in doing so, they were able to detect and describe the spatial distribution of the cold-water coral Desmophyllum dianthus that grows along the course of the fjord over its entire pH gradient, based on data that were acquired via SCUBA diving in 2004, 2005, 2007 and 2011, or by means of video transects obtained by a remotely-operated vehicle in 2004, 2005 and 2007.

What was learned
From this host of data, the seven scientists determined that the cold-water coral D. dianthus grows along the course of the fjord and its entire pH range," where "it occurs in shallow depths (below 12 m, pH 8.1) as part of a deep-water emergence community, but also in [water of] 225 m depth at a pH of 7.4." Indeed, they say that it thrives close to the aragonite saturation horizon and even below it, where they found "flourishing coral banks."

What it means
In discussing their findings within a wider context, Jantzen et al. note that several other recent studies "question reduced calcification rates of corals in environments with lowered aragonite saturation state (Ωarg)," citing Marubini et al. (2008) and Jury et al. (2010), while noting that "very recent studies hint at a higher acclimatization potential of cold-water corals to ocean acidification," citing Rodolfo-Metalpa et al. (2010), Trotter et al. (2011), Form and Riebesel (2012) and McCulloch et al. (2012a,b). And now their study suggests much the same thing.

References
Form, A. and Riebesel, U. 2012. Acclimation to ocean acidification during long-term CO2 exposure in the cold-water coral Lophelia pertusa. Global Change Biology 18: 843-853.

Jury, C., Whitehead, R.F. and Szmant, A. 2010. Effects of variations in carbonate chemistry on the calcification rates of Madracis auretenra (= Madracis mirabilis sensu Wells, 1973): bicarbonate concentrations best predict calcification rates. Global Change Biology 16: 1632-1644.

Marubini, F., Ferrier-Pages, C., Furla, P. and Allemande, D. 2008. Coral calcification responds to seawater acidification, a working hypothesis towards a physiological mechanism. Coral Reefs 27: 491-499.

McCulloch, M., Falter, J., Trotter, J. and Montagna, P. 2012a. Coral resilience to ocean acidification and global warming through pH up-regulation. Nature Climate Change 2: 1-5.

McCulloch, M., Trotter, J., Montagna, P., Falter, J., Dunbar, R., Freiwald, A., Forsterra, G., Lopez-Correa, M., Maier, C., Ruggeberg, A. and Taviani, M. 2012b. Resilience of cold-water scleractinian corals to ocean acidification: boron isotopic systematics of pH and saturation state up-regulation. Geochimica et Cosmochimica Acta 87: 21-34.

Rodolfo-Metalpa, R., Martin, S., Ferrier-Pages, C. and Gattuso, J.P. 2010. Response of the temperate coral Cladocora caespitosa to mid- and long-term exposure to pCO2 and temperature levels projected for the year 2100 AD. Biogeosciences 7: 289-300.

Trotter, J., Montagna, P., McCulloch, M., Silenzi, S., Reynaud, S., Mortimer, G., Martin, S., Ferrier-Pages, C., Gattuso, J.P. and Rodolfo-Metalpa, R. 2011. Quantifying the pH 'vital effect' in the temperate zooxanthellate coral Cladocora caespitosa: validation of the boron seawater pH proxy. Earth and Planetary Science Letters 303: 163-173.