[Coral-List] Are there really almost no studies that show a decline in gross calcification under low pH?

Thomas Krueger thomas.krueger at epfl.ch
Mon Apr 4 13:49:38 EDT 2016

Given the vast number of studies that show a decline in net 
calcification in individual corals as well as reef communities within 
the scope of a projected 2100 average ocean pH of around 7.8, I was 
wondering why there are only so few studies that have investigated the 
effect of low pH on the biologically determined gross calcification 
performance (i.e., before any deductions for skeleton dissolution have 
been made). In fact, we found only four (not counting Gagnon et al 
2013). While Houlbreque et al. 2012 (Coral Reefs 31(1) 101-109) found 
initially no effect of pH 7.8 and 7.5 on gross calcification in 
Stylophora, it was half the control value for the same coral in a later 
study (Houlbreque et al 2015; L&O 60(1) 89-99). See also Tambutte et al 
2015 (Nature communications DOI: 10.1038/ncomms8368) for no effect of pH 
7.8 on porosity or linear extension in Stylophora pistillata (all three 
studies used Red Sea specimen). The work of Rodolfo-Metalpa et al. 2011 
(Nature Climate Change DOI: 10.1038/NCLIMATE1200) demonstrated that two 
Mediterranean corals along a CO2 gradient show either no significant 
change or an actual increase in gross calcification for a pH of 7.7. 
Similarly, a later study by Rodolfo-Metalpa et al. 2015 (Global Change 
Biology 21, 2238–2248) shows no effect of pH 7.7 on the gross 
calcification in three cold water corals. What studies are we missing? 
Has nobody really observed changes in coral gross calcification in 
response to a "realistic" lower than ambient pH, which would indicate 
that the observed changes in net calcification for many of these corals 
are largely dissolution effects of existing skeleton. I am grateful for 
any helpful comments on this matter.

*Thomas Krueger */Postdoctoral Researcher/

Laboratory for Biological Geochemistry | École polytechnique fédérale de 
Lausanne (EPFL)

*P*: (+41) 21 69 38039

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