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Potential Effects of Diel-Cycling Hypoxia and pH on Oyster Growth

Paper Reviewed
Keppel, A.G., Breitburg, D.L. and Burrell, R.B. 2016. Effects of Co-Varying Diel-Cycling Hypoxia and pH on Growth in the Juvenile Eastern Oyster, Crassostrea virginica. PLOS ONE | DOI:10.1371/journal.pone.0161088.

Introducing their intriguing study, Keppel et al. (2016) write that "shallow water provides important habitat for many species, but also exposes these organisms to daily fluctuations in dissolved oxygen (DO) and pH caused by cycles in the balance between photosynthesis and respiration that can contribute to repeated, brief periods of hypoxia and low pH (caused by elevated pCO2)," noting also that "the amplitude of these cycles, and the severity and duration of hypoxia and hypercapnia that result, can be increased by eutrophication, and are predicted to worsen with climate change."

In light of these facts and associated speculations, the three U.S. researchers describe how they conducted "laboratory experiments to test the effects of both diel-cycling and constant low DO and pH (elevated pCO2) on growth of the juvenile eastern oyster (Crassostrea virginica), an economically and ecologically important estuarine species." And what did they learn from their study of the subject?

Keppel et al. determined that "juvenile oysters have [1] an ability to acclimate to, and [2] ultimately compensate for, the negative effects of hypoxia on growth, as well as [3] an ability under some circumstances to withstand exposure to co-varying cycling hypoxia as low as 0.5 mg/liter and [4] pH as low as 7.0 without reductions in growth." Thus, it would appear this marine organism didn't get the climate-alarmist memo that rising atmospheric CO2 concentrations would be their doom.

Posted 12 December 2016