How does rising atmospheric CO2 affect marine organisms?

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Impacts of Elevated CO2 on Growth and Calcification of Two Species of Oyster Larvae
Miller, A.W., Reynolds, A.C., Sobrino, C. and Riedel, G.F. 2009. Shellfish face uncertain future in high CO2 world: Influence of acidification on oyster larvae calcification and growth in estuaries. PLoS ONE 4: 10.1371/journal.pone.0005661.

What was done
In an effort designed to evaluate potential CO2-induced changes in estuarine calcification in the years ahead, larvae of two oyster species -- the Eastern oyster (Crassostrea virginica) and the Suminoe oyster (Crassostrea ariakensis) -- were grown for up to 28 days in estuarine water in equilibrium with air of four different CO2 concentrations (280, 380, 560 and 800 ppm), which were chosen to represent atmospheric conditions in the pre-industrial era, the present day, and the years 2050 and 2100, respectively, as projected by the IS92a business-as-usual scenario of the IPCC, and which were maintained by periodically aerating the different aquaria employed in the study with air containing 1% CO2, while larval growth was assessed via image analysis and calcification was determined by means of chemical analyses of calcium in the shells of the oyster larvae.

What was learned
Miller et al. report that when the larvae of both species were cultured continuously from 96 hours post fertilization for 26 to 28 days while exposed to elevated CO2 concentrations, they "appeared to grow, calcify and develop normally with no obvious morphological deformities, despite conditions of significant aragonite undersaturation," stating that these findings "run counter to expectations that aragonite shelled larvae should be especially prone to dissolution at high pCO2." More specifically, they state that "both oyster species generated larval shells that were of similar mean thickness, regardless of pCO2, Oarag [aragonite compensation point] or shell area," remarking that they "interpret the pattern of similar shell thickness as further evidence of normal larval shell development."

What it means
Clearly, these two calcifying organisms appear not to suffer the deleterious consequences so frequently claimed by climate alarmists to accompany the ongoing rise in the air's CO2 content; and, consequently, the four researchers conclude that "biological responses to acidification, especially [in] calcifying biota, will be species specific and therefore much more variable and complex than reported previously." And, we would add, they will probably be a whole lot less significant as well. See Oceans (Acidification) in our Subject Index.

Reviewed 9 June 2010