Volume 13, Number 18: 5 May 2010
In the introductory material to their paper on potential effects of predicted near-future increases in CO2-driven ocean acidification on shell-producing calcification in a certain species of oyster, Watson et al. (2009) report that over the past two centuries, CO2 emissions from deforestation and the burning of fossil fuels have increased atmospheric CO2 concentrations from 280 to 380 ppm, citing NOAA/ESRL records produced and maintained by Pieter Tans. They additionally say that the portion of this extra CO2 that has been taken up by the planet's oceans has caused a 0.1 unit drop in the pH of their surface waters, which would appear to be correct. However, they predict there will be a further reduction in ocean pH of 0.3 to 0.5 units by 2100, citing the work of Haugan and Drange (1996), Orr et al. (2005) and Caldeira and Wickett (2005), while noting that these predicted changes in ocean pH "are not only greater but far more rapid than any experienced in the last 24 million years," citing Blackford and Gilbert (2007), or "possibly the last 300 million years," citing Caldeira and Wickett (2003), which all sounds pretty scary. But does it seem just a bit too scary? ... as in too scary to be true?
Consider the findings of Tans himself, who Watson et al. approvingly cite in regard to the CO2 history they mention. In a paper published in Oceanography, which we have briefly discussed in a prior Editorial, Tans (2009) concluded that the future trajectory of oceanic pH will likely be significantly different from that suggested by the scientists cited by Watson et al., while at the same time bravely criticizing the IPCC reports that have also accepted the highly inflated acidification predictions of those scientists. Indeed, whereas Watson et al. and the IPCC accept the claims of those who project a decline in pH somewhere in the range of 0.3 to 0.5 between now and the end of the century, Tans' projections yield a pH decline somewhere in the range of 0.09 to 0.17, which is much smaller, and which would be expected to have significantly reduced biological impacts compared to those suggested by the experimental work of Watson et al. for that future point in time.
Based on the results of their experiments and the maximum decline in ocean-water pH that they accept, for example, Watson et al. predict a significant decline of 72% in Sydney rock oyster (Saccostrea glomerata) larval survival by the year 2100. However, utilizing Watson et al.'s data, but with the maximum ocean-water pH decline calculated by Tans, we obtain a non-significant larval survival decline of only 14%, based on our interpolation of the graphical results portrayed in Watson et al.'s paper. In like manner, similar assessments of changes in antero-posterior measurement yield a significant decline of 8.7% using Watson et al.'s assumptions about ocean pH, but a non-significant decline of only 1.8% according to Tans' pH calculations. Corresponding results for dorso-ventral measurement were a significant decline of 7.5% with Watson et al.'s pH values, but a non-significant decline of only 1.5% with Tans' values; while for larval dry mass there was a decline of 50% in Watson et al.'s analysis, but an actual increase (albeit non-significant) of 6% using Tans' pH analysis. Last of all, for empty shells remaining there was a significant decline of 90% in the Watson et al. study, but a non-significant decline of only 6% when Tans' pH projections were used.
In summation, based on their experimental data and the ocean pH projections for the end of the century that are promoted by them and the IPCC, Watson et al. find what they characterize as "a dramatic negative effect on the survival, growth, and shell formation of the early larval stages of the Sydney rock oyster." On the other hand, employing the pH values projected by Tans, there are no statistically significant reductions in any of the five biological parameters measured and evaluated by Watson et al., which is an amazingly benign response to an environmental threat that is being suggested by some to be more serious or extreme than it was at any other time that it may have reared its ugly head over the past 300 million years!
Sherwood, Keith and Craig Idso
References
Blackford, J.C. and Gilbert, F.J. 2007. pH variability and CO2 induced acidification in the North Sea. Journal of Marine Systems 64: 229-241.
Caldeira, K. and Wickett, M.E. 2003. Anthropogenic carbon and ocean pH. Nature 425: 365.
Caldeira, K. and Wickett, M.E. 2005. Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean. Journal of Geophysical Research 110: 10.1029/2004JC002671.
Haugan, P.M. and Drange, H. 1996. Effects of CO2 on the ocean environment. Energy Conversion and Management 37: 1019-1022.
Orr, J.C., Fabry, V.J., Aumont, O., Bopp, L., Doney, S.C., Feely, R.A., Gnanadesikan, A., Gruber, N., Ishida, A., Joos, F., Key, R.M., Lindsay, K., Maier-Reimer, E., Matear, R., Monfray, P., Mouchet, A., Najjar, R.G., Plattner, G.-K., Rodgers, K.B., Sabine, C.L., Sarmiento, J.L., Schlitzer, R., Slater, R.D., Totterdell, I.J., Weirig, M.-F., Yamanaka, Y. and Yool, A. 2005. Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature 437: 681-686.
Tans, P. 2009. An accounting of the observed increase in oceanic and atmospheric CO2 and an outlook for the future. Oceanography 22: 26-35.
Watson, S.-A., Southgate, P.C., Tyler, P.A. and Peck, L.S. 2009. Early larval development of the Sydney rock oyster Saccostrea glomerata under near-future predictions of CO2-driven ocean acidification. Journal of Shellfish Research 28: 431-437.