What was done
The authors obtained nubbins (small live coral samples) by cutting off terminal portions of branches of a parent colony, after which they glued them onto glass slides and grew them in five experimental tanks that were continuously supplied with Mediterranean seawater maintained at five different temperatures (21, 23, 25, 27, and 29°C) for a period of 12 weeks, during which time the growing nubbins were fed once a week with Artemia salina nauplii, while their calcification rates were assessed by means of once-a-week weighings.

What was learned
In the words of the seven researchers, there was "a clear positive linear correlation, which can be parameterized as: Rate of Calcification (%/day) = 0.034 x T (°C) - 0.645 (R² = 0.99," such that "calcification rates ranged from 0.061 ± 0.009 %/day to 0.346 ± 0.032 %/day at 21 and 29°C, respectively," which "corresponds to a 5.7-fold increase in calcification rate from the lowest to the highest water temperature."

What it means
The findings of Reynaud et al. add yet another set of experimental data to the growing body of evidence which clearly demonstrates that coral calcification rates tend to rise in essentially linear fashion with rising water temperatures over the ranges encountered by most corals in their natural habitats. See, for example, the studies of Clausen and Roth (1975), Coles and Coles (1977), Kajiwara et al. (1995), Nie et al. (1997), Lough and Barnes (1997, 2000), Reynaud-Vaganay et al. (1999), Bessat and Buigues (2001), Carricart-Ganivet (2004) and McNeil et al. (2004).

References
Bessat, F. and Buigues, D. 2001. Two centuries of variation in coral growth in a massive Porites colony from Moorea (French Polynesia): a response of ocean-atmosphere variability from south central Pacific. Palaeogeography, Palaeoclimatology, Palaeoecology 175: 381-392.

Carricart-Ganivet, J.P. 2004. Sea surface temperature and the growth of the West Atlantic reef-building coral Montastraea annularis. Journal of Experimental Marine Biology and Ecology 302: 249-260.

Clausen, C.D. and Roth, A.A. 1975. Effect of temperature and temperature adaptation on calcification rate in the hematypic Pocillopora damicornis. Marine Biology 33: 93-100.

Coles, S.L. and Coles. P.L. 1977. Effects of temperature on photosynthesis and respiration in hermatypic corals. Marine Biology 43: 209-216.

Kajiwara, K., Nagai, A. and Ueno, S. 1995. Examination of the effect of temperature, light intensity and zooxanthellae concentration on calcification and photosynthesis of scleractinian coral Acropora pulchra. J. School Mar. Sci. Technol. 40: 95-103.

Lough, J.M. and Barnes, D.J. 2000. Environmental controls on growth of the massive coral Porites. Journal of Experimental Marine Biology and Ecology 245: 225-243.

McNeil, B.I., Matear, R.J. and Barnes, D.J. 2004. Coral reef calcification and climate change: The effect of ocean warming. Geophysical Research Letters 31: 10.1029/2004GL021541.

Nie, B., Chen, T., Liang, M., Wang, Y., Zhong, J. and Zhu, Y. 1997. Relationship between coral growth rate and sea surface temperature in the northern part of South China Sea. Sci. China Ser. D 40: 173-182.

Reynaud-Vaganay, S., Gattuso, J.P., Cuif, J.P., Jaubert, J. and Juillet-Leclerc, A. 1999. A novel culture technique for scleractinian corals: Application to investigate changes in skeletal δ¹⁸O as a function of temperature. Marine Ecology Progress Series 180: 121-130.