The importance of accurate CO2 dosing and measurement in ocean acidification studies

Chung et al. (Chung et al., 2014) recently reported the results of a study investigating the effect of dissolved CO2 level on the retinal response of a marine fish. The two CO2 concentrations tested represented different ocean acidification scenarios. The lower concentration represented a near-future CO2 concentration (466 μatm), and the other a 2100 scenario with elevated CO2 due to anthropogenic inputs (944 μatm). Such studies are timely given the high probability that atmospheric CO2 concentration will continue to increase. The results will likely be incorporated into future Intergovernmental Panel on Climate Change reports, and may form part of future action plans designed to preserve species and
ecosystem viability. For this reason, it is crucial to ensure that any testing of future ocean acidification scenarios is carried out with a high degree of certainty about the CO2 levels tested.

The methods Chung et al. used to both quantify and dose CO2 in their study lack the necessary accuracy and precision to definitively assert that the target CO2 test levels were correct. The key problem is their dependence on pH measurements made with a glass potentiometric electrode and low ionic concentration calibration buffers (a method commonly employed by a number of the authors on this paper), which is not recommended best practice for the accurate determination of pH in waters of high ionic concentration (Dickson, 2010), such as seawater. (…)

Moran D., 2014. The importance of accurate CO2 dosing and measurement in ocean acidification studies. The Journal of Experimental Biology 217:1828-1829. Article (subscription required).

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