How does rising atmospheric CO2 affect marine organisms?

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Peanuts Perform Well in High-CO2 Air
Vu, J.C.V.  2005.  Acclimation of peanut (Arachis hypogaea L.) leaf photosynthesis to elevated growth CO2 and temperature.  Environmental and Experimental Botany 53: 85-95.

What was done
The author grew peanuts (Arachis hypogaea L. cv. Florunner) from seed to maturity in greenhouses maintained at atmospheric CO2 concentrations of 360 and 720 ppm and at air temperatures that were 1.5 and 6.0C above outdoor air temperatures, while they measured a number of parameters related to the plants' photosynthetic performance.

What was learned
Vu reports that although Rubisco protein content and activity were down-regulated by elevated CO2, Rubisco photosynthetic efficiency - the ratio of midday light-saturated carbon exchange rate to Rubisco initial or total activity - of the elevated-CO2 plants "was 1.3- to 1.9-fold greater than that of the ambient-CO2 plants at both growth temperatures."  He also determined that "leaf soluble sugars and starch of plants grown at elevated CO2 were 1.3- and 2-fold higher, respectively, than those of plants grown at ambient CO2."  In addition, he discovered that the leaf transpiration of the elevated-CO2 plants relative to that of the ambient-CO2 plants was 12% less at near-ambient temperatures and 17% less in the higher temperature regime, while the water use efficiency of the elevated-CO2 plants relative to the ambient-CO2 plants was 56% greater at near-ambient temperatures and 41% greater in the higher temperature environment.

What it means
Vu notes that because less Rubisco protein was required by the elevated-CO2 plants, the subsequent redistribution of excess leaf nitrogen "would increase the efficiency of nitrogen use for peanut under elevated CO2," just as the optimization of inorganic carbon acquisition and greater accumulation of the primary photosynthetic products in the CO2-enriched plants "would be beneficial for peanut growth at elevated CO2."  Indeed, in the absence of other stresses, Vu's ultimate conclusion is that "peanut photosynthesis would perform well under rising atmospheric CO2 and temperature predicted for this century."

Reviewed 23 February 2005