Crustose Coralline Algae in a CO2-Enriched Ocean
Nash, M.C., Opdyke, B.N., Troitzsch, U., Russell, B.D., Adey, W.H., Kato, A., Diaz-Pulido, G., Brent, C., Gardner, M., Prichard, J. and Kline, D.I. 2012. Dolomite-rich coralline algae in reefs resist dissolution in acidified conditions. Nature Climate Change 3: 268-272.
Taking their own advice, the eleven researchers, as they describe it, "carried out dissolution experiments on fragments of CCA that were collected fresh, but then dried, from the Heron Island reef front (Great Barrier Reef, Australia), after which they were exposed to ambient sea water as a control and an enriched CO2 treatment, where "pH ranged from 7.85 to 8.55 (control) and 7.69-8.44 (treatment), tracking natural diurnal changes measured in the lagoon water."
So what did they find?
Nash et al. (2012) determined, in their words, that "dried dolomite-rich CCA have 6-10 times lower rates of dissolution than predominantly Mg-calcite CCA in both high-CO2 (~700 ppm) and control (~380 ppm) environments." And they say that they found this stabilizing mechanism to be due to "a combination of reduced porosity due to dolomite infilling and selective dissolution of other carbonate minerals."
And what is the real-world significance of this finding?
Due to the fact, as they put it, that "the prevailing theories that Mg-calcites with higher Mg content will undergo greatest dissolution, we were surprised to find a trend in the opposite direction." And since dolomite-rich CCA frameworks are common in shallow coral reefs globally, they conclude "it is likely that they will continue to provide protection and stability for coral reef frameworks as CO2 rises."
Nash, M.C., Troitzsch, U., Opdyke, B.N., Trafford,,J.M., Russell, B.D. and Kline, D.I. 2011. First discovery of dolomite and magnesite in living coralline algae and its geobiological implications. Biogeosciences 8: 3331-3340.