Background
The authors write that "subsea geological storage of CO2 is considered a potentially attractive means of reducing anthropogenic emissions and involves injecting liquefied CO2 into porous rock formations deep below the seafloor for permanent disposal," but they say "there is an estimated 34% chance of a leak occurring from the storage site within 1000 years (Turley et al., 2004)." Thus, they felt it imperative to determine the consequences of such a CO2 leak for creatures that inhabit the deep sea.

What was done
Hammer et al. exposed specimens of the deep-sea bivalve Acesta excavata that they collected from cold-water reefs to water maintained in equilibrium with an atmospheric CO2 concentration of approximately 33,000 ppm that resulted in a pH value of 6.35 - corresponding to conditions reported for water in close proximity to natural CO2 seeps on the ocean floor - for periods of 0.5, 1, 4, 12, 24 or 96 hours, after which the bivalves were returned to normal CO2/pH conditions for 1, 4, 12, 24 or 96 hours, during which periods they measured a number of their physiological functions.

What was learned
The three researchers report that their exposure of A. excavata to water in equilibrium with the super-high CO2 concentration they employed in their study "induced extra- and intra-cellular acidosis that remained uncompensated during exposure," and they say that "oxygen consumption dropped significantly during the initial phase." However, they found that it "approached control values at the end of exposure" and that "no mortality was observed in exposed animals."

What it means
In the words of the researchers who conducted the study, they say their results suggest that "A. excavata displays higher tolerance to severe environmental hypercapnia [a condition where there is too much CO2 in the blood] than what may be expected for deep-sea animals." However, they note that Tunnicliffe et al. (2009) "found evidence that permanent exposure to similar conditions causes reduced growth rates and shell thickness in mussels adapted to live at deep-sea vents," and they speculate that "such long-term effects may also develop in A. excavata." On the other hand, they note that previous studies on other species that mostly involved exposure to moderate hypercapnia (PCO2 = 10,000 ppm or less) found that complete compensation of extracellular acidosis has frequently been observed in fish, citing Heisler (1984, 1986), and that "marine invertebrates are often able to partially counteract acidosis through accumulation of bicarbonate ions," citing the work of Lindinger et al. (1984), Portner et al. (1988), Michaelidis et al. (2005), Miles et al. (2007), Pane and Barry (2007) and Gutowska et al. (2010). And, of course, such unusually high atmospheric CO2 concentrations are far more extreme than any expected to occur in the real world by even the most rabid of climate alarmists, which suggests that the marine life investigated by this collection of scientists should not be unduly stressed by future anthropogenic CO2 emissions.

References
Gutowska, M., Melzner, F., Langenbuch, M., Bock, C., Claireaux, G. and Portner, H. 2010. Acid-base regulatory ability of the cephalopod (Sepia officinalis) in response to environmental hypercapnia. Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 180: 323-334.

Heisler, N. 1984. Acid-base regulation in fishes. In: Hoar, W.S. and Randall, D.J. (Eds.). Fish Physiology. Academic Press, New York, New York, USA, pp. 315-401.

Heisler, N. 1986. Buffering and transmembrane ion transfer processes. In: Heisler, N. (Ed.). Acid-Base Regulation in Animals. Elsevier Science Publishers BV. Amsterdam, The Netherlands, pp. 3-47.

Lindinger, M.I., Lauren, D.J. and McDonald, G. 1984. Acid-base balance in the sea mussel Mytilus edulis. III. Effects of environmental hypercapnia on intra- and extra-cellular acid-base balance. Marine Biology Letters 5: 371-381.

Michaelidis, B., Ouzounis, C., Paleras, A. and Portner, H.O. 2005. Effects of long-term moderate hypercapnia on acid-base balance and growth rate in marine mussels Mytilus galloprovincialis. Marine Ecology Progress Series 293: 109-118.

Miles, H., Widdicombe, S., Spicer, J.I. and Hall-Spencer, J. 2007. Effects of anthropogenic seawater acidification on acid-base balance in the sea urchin Psammechinus miliaris. Marine Pollution Bulletin 54: 89-96.

Pane, E.F. and Barry, J.P. 2007. Extracellular acid-base regulation during short-term hypercapnia is effective in a shallow-water crab, but ineffective in a deep-sea crab. Marine Ecology Progress Series 334: 1-9.

Portner, H.O., Reipschlager, A. and Heisler, N. 1998. Acid-base regulation, metabolism and energetics in Sipunculus nudus as a function of ambient carbon dioxide level. Journal of Experimental Biology 201: 43-55.

Tunnicliffe, V., Davies, K.T.A., Butterfield, D.A., Embley, R.W., Rose, J.M., Chadwick Jr., W.W. 2009. Survival of mussels in extremely acidic waters on a submarine volcano. Nature Geocience 2: 344-348.