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Coralline Algae Exposed to Variable pCO2: Prepped for the Future?
Johnson, M.D., Moriarty, V.W. and Carpenter, R.C. 2014. Acclimatization of the crustose coralline alga Porolithon onkodes to variable pCO2. PLOS ONE 9: e87678.

The authors write that seawater chemistry "in near shore coastal ecosystems, such as upwelling regions (Fabry et al., 2008; Thomsen et al., 2010), coral reefs (Ohde and van Woesik, 1999; Gagliano et al., 2010; Price et al., 2012; Hall-Spencer et al., 2008), estuarine systems, kelp forests (Holmann et al., 2011) and natural CO2 vents (Hall-Spencer et al., 2008; Fabricius et al., 2011; Kerrison et al., 2011; Crook et al., 2012), is both spatially and temporally dynamic within a habitat (Andersson and Mackenzie 2012)," so that in these ecosystems "swings in diel pH frequently exceed the forecasted projections of ocean acidification for the end of the century (Holmann et al., 2011; Price et al., 2012; Suzuki et al., 1995; Yates and Halley 2006; Bates et al., 2010)." And thus the question naturally arises: Are coralline algae that live in these environments already primed to successfully live in higher pCO2 environments?

What was done
Intrigued by this possibility, Johnson et al. exposed samples of the crustose coralline alga (Porolithon onkodes) that they collected from low and high pCO2 variability sites on a back reef characterized by unidirectional water flow in Moorea, French Polynesia, while quantifying the effects of these treatments on algal calcification, which they did "by measuring the change in buoyant weight," and on algal metabolism, which they did "by conducting sealed incubations to measure rates of photosynthesis and respiration."

What was learned
In a nutshell, the three U.S. researchers report that "corallines from the high variability habitat calcified 42% more than corallines from the low variability habitat."

What it means
As a result of their findings, Johnson et al. write that "the significance of the original habitat of the coralline calcification response to variable, high pCO2 indicates that individuals existing in dynamic pCO2 habitats may be acclimatized to ocean acidification within the scope of in situ variability." And they thus end their paper by saying that "given the potential dire consequences of ocean acidification for coastal ecosystems, it is important to consider how acclimatization may facilitate the survival of marine organisms in the near future," which is (1) something that many people are failing to do, and which (2) makes potential consequences of ocean acidification nowhere near as dire as many people have long believed they could be.

Anderson, A.J. and Mackenzie, F.T. 2012. Revisiting four scientific debates in ocean acidification research. Biogeosciences 9: 893-905.

Bates, N.R., Amat, A. and Andersson, A.J. 2010. Feedbacks and responses of coral calcification on the Bermuda reef system to seasonal changes in biological processes and ocean acidification. Biogeosciences 7: 2509-2530.

Crook, E.D., Potts, D., Rebolledo-Vieyra, M., Hernandez, L. and Paytan, A. 2012. Calcifying coral abundance near low-pH springs: implications for future ocean acidification. Coral Reefs 31: 239-245.

Fabricius, K.E., Langdon, C., Uthicke, S., Humphrey, C., Noonan, S., De'ath, G., Okazaki, R., Muehllehner, N., Glas, M.S. and Lough, J.M. 2011. Losers and winners in coral reefs acclimatized to elevated carbon dioxide concentrations. Nature Climate Change 1: 165-169.

Fabry, V.J., Seibel, B.A., Feely, R.A. and Orr, J.C. 2008. Impacts of ocean acidification on marine fauna and ecosystem processes. ICES Journal of Marine Science 65: 414-432.

Gagliano, M., Mccormick, M.I., Moore, J.A. and Depczynski, M. 2010. The basics of acidification: baseline variability of pH on Australian coral reefs. Marine Biology 157: 1849-1856.

Hall-Spencer, J.M., Rodolfo-Metalpa, R., Martin, S., Ransome, E., Fine, M., Turner, S.M., Rowley, S.J., Tedesco, D. and Buia, M.-C. 2008. Volcanic carbon dioxide vents show ecosystem effects of ocean acidification. Nature 454: 96-99.

Holmann, G.E., Smith, J.E., Johnson, K.S., Send, U., Levin, L.A., Micheli, F., Paytan, A., Price, N.N., Peterson, B., Takeshita, Y., Matson, P.G., Crook, E.D., Kroeker, K.J., Gambi, M.C., Dohrn, A., Rivest, E.B., Frieder, C.A., Yu, P.C. and Martz, T.R. 2011. High-frequency dynamics of ocean pH: a multi-ecosystem comparison. PLOS ONE 6: e28983.

Kerrison, P., Hall-Spencer, J.M., Suggett, D.J., Hepburn, I.J. and Steinke, M. 2011. Asssessment of pH variability at a coastal CO2 vent for ocean acidification studies. Estuarine, Coastal and Shelf Science 94: 129-137.

Ohde, S. and van Woesik, R. 1999. Carbon dioxide flux and metabolic processes of a coral reef, Okinawa. Bulletin of Marine Science 65: 559-576.

Price, N.N., Martz, T.R., Brainard, R.E. and Smith, J.E. 2012. Diel variability in seawater pH relates to calcification and benthic community structure on coral reefs. PLOS ONE 7: e43843.

Suzuki, A., Nakamori, T. and Kayanne, H. 1995. The mechanism of production enhancement in coral reef carbonate systems: model and empirical results. Sedimentary Geology 99: 259-280.

Thomsen, J., Gutowska, M.A., Saphorster, J., Heinemann, A., Trubenbach, K., Fietzke, J., Hiebenthal, C., Eisenhauer, A., Körtzinger, A., Wahl, M. and Melzner, F. 2010. Calcifying invertebrates succeed in a naturally CO2-rich coastal habitat but are threatened by high levels of future acidification. Biogeosciences 7: 3879-3891.

Yates, K.K. and Halley, R.B. 2006. CO32- concentration and pCO2 thresholds for calcification and dissolution on the Molokai reef flat, Hawaii. Biogeosciences 3: 357-369.

Reviewed 7 May 2014