Peer-reviewed Papers on Coral

There are two recent papers that go against the IPCC/alarmist propaganda. The first, published in Geochimica et Cosmochimica Acta 67: 1129-1143, by Thresher et al. Their data clearly suggest, as they describe it, that "a change in carbonate saturation horizons per se as a result of ocean acidification is likely to have only a slight effect on most of the live deep-sea biogenic calcifiers," which is a most reassuring result.

Thresher, R.E., Tilbrook, B., Fallon, S., Wilson, N.C. and Adkins, J. 2011. Effects of chronic low carbonate saturation levels on the distribution, growth and skeletal chemistry of deep-sea corals and other seamount megabenthos. Marine Ecology Progress Series 442: 87-99. 

The authors state that ocean acidification results from a net uptake of CO2 emissions that causes a decrease in the carbonate ion concentration of the ocean, which has been "forecast to hamper production of biogenic carbonates (aragonite and calcite) in the skeletons, shells and tests of marine taxa (Orr et al., 2005; Moy et al., 2009)," thereby "threatening their long-term viability and severely impacting marine ecosystems." They go on to note, however, that these predictions "are based primarily on modeling studies and short-term laboratory exposure to low-carbonate conditions," citing Riegl et al. (2009), Veron et al. (2009) and Ries et al. (2010). And they say that "their relevance to long-term exposure in the field and the potential for ecological or evolutionary adjustment are uncertain," citing Maynard et al. (2008).

What was learned
The five researchers report that they "found little evidence that carbonate under-saturation to at least -30% affected the distribution, skeletal composition, or growth rates of corals and other megabenthos on Tasmanian seamounts." In fact, they found that "both solitary scleractinian corals and colonial gorgonians were abundant at depths well below their respective saturation horizons and appeared healthy," while HMC echinoderms were common to as deep as they sampled (4011 m), in water that was approximately 45% under-saturated. They also report that "for both anthozoan and non-anthozoan taxa, there was no obvious difference in species' maximum observed depths as a function of skeletal mineralogy." In other words, the community "was not obviously shifted towards taxa with either less soluble or no skeletal structure at increasing depth." And in light of these observations, they write that "it is not obvious from our data that carbonate saturation state and skeletal mineralogy have any effect on species' depth distributions to the maximum depth sampled," and they say that they also saw "little evidence of an effect of carbonate under-saturation on growth rates and skeletal features."

Commenting further on their findings, Thresher et al. write that "the observation that the distributions of deep-sea corals are not constrained by carbonate levels below saturation is broadly supported by the literature," noting that "solitary scleractinians have been reported as deep as 6 km (Fautin et al., 2009) and isidid gorgonians as deep as 4 km (Roark et al., 2005)." And they say that their own data also "provide no indication that conditions below saturation per se dictate any overall shifts in community composition."
As for why things were as they observed them to be, the researchers note, as highlighted by Cohen and Holcomb (2009), that one or more cell membranes may envelope the organisms' skeletons, largely isolating the calcification process and its associated chemistry from the bulk seawater, citing the studies of McConnaughey (1989), Adkins et al. (2003) and Cohen and McConnaughey (2003), which phenomenon could presumably protect "the skeleton itself from the threat of low carbonate dissolution." In addition, they note that "calcification is energetically expensive, consuming up to 30% of the coral's available resources, and that normal calcification rates can be sustained in relatively low-carbonate environments under elevated feeding or nutrient regimes," as described in detail by Cohen and Holcomb (2009), stating that the likelihood that "elevated food availability could compensate for the higher costs of calcification in heterotrophic deep-sea species appears plausible."

The second paper by Shamberger et al published in Marine Chemistry 127: 64-75 . They conclude:  "it appears that while calcification rate and Ωarag are correlated within a single coral reef ecosystem," as in the case of the barrier reef of Kaneohe Bay, "this relationship does not necessarily hold between different coral reef systems," and they state that it can thus be expected that "ocean acidification will not affect coral reefs uniformly and that some may be more sensitive to increasing pCO2 levels than others," which also means (taking a more positive view of the subject) that some may be less sensitive to increasing pCO2 than others.

CO2 Science adds in light of what we know about the potential for rapid evolution in corals and their symbionts - see Evolution (Aquatic Life) in our Subject Index - we can validly maintain an even stronger positive view of the subject.

Shamberger, K.E.F., Feely, R.A., Sabine, C.L., Atkinson, M.J., DeCarlo, E.H. and Mackenzie, F.T. 2011. Calcification and organic production on a Hawaiian coral reef. Marine Chemistry 127: 64-75.  

What was done
In a study that sheds new light on this subject, Shamberger et al. deployed newly designed "autosamplers" to collect water samples from the barrier coral reef of Kaneohe Bay, Oahu, Hawaii, every two hours for six 48-hour periods, two each in June 2008, August 2009 and January/February 2010. And based on these seawater measurements, they calculated net ecosystem calcification (NEC) and net photosynthesis (NP) rates for these periods.

What was learned
As expected, the six scientists found that "daily NEC was strongly negatively correlated with average daily pCO2, which ranged from 421 to 622 ppm." Most interestingly, however, they report that "daily NEC of the Kaneohe Bay barrier reef is similar to or higher than daily NEC measured on other coral reefs, even though Ωarag levels (mean Ωarag = 2.85) are some of the lowest measured in coral reef ecosystems [italics added]."

Read more at CO2 science HERE and Here.