How does rising atmospheric CO2 affect marine organisms?

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CO2 Effects on Cork Oak Seedlings Exposed to High Light and Water Stress
Pardos, M., Puertolas, J., Aranda, I. and Pardos, J.A. 2006. Can CO2 enrichment modify the effect of water and high light stress on biomass allocation and relative growth rate of cork oak seedlings? Trees 20: 713-724.

What was done
Seedlings of cork oak (Quercus suber L., described by the authors as "a typical Mediterranean species") were germinated from acorns collected from trees near Toledo, Spain, and grown for five months - one per each 3-L pot filled with a mixture of fine sand and peat maintained at either high (83%) or low (32-34%) growing medium moisture - under either high (600 Ámol m-2 s-1) or low (60 Ámol m-2 s-1) light intensity in growth chambers maintained at either ambient (360 ppm) or elevated (700 ppm) atmospheric CO2 concentration.

What was learned
Among other things, Pardos et al. report that seedling relative growth rate rose 2.2-fold when going from the lowest to the highest combined light-water treatment in the elevated CO2 environment, but only 1.6-fold when doing so in the ambient CO2 environment. In addition, they say that "cork oak showed particularly large increases in biomass in response to elevated CO2 under low-watered and high-illuminated conditions."

What it means
The four Spanish researchers say that "elevated CO2 caused cork oak seedlings to improve their performance in dry and high light environments to a greater extent than under well-irrigated and low-light conditions, thus ameliorating the effects of soil water stress and high light loads on growth [our italics]." Consequently, and because they believe these latter two stressful conditions are what "global change is likely to produce in the Mediterranean basin in the next decades," it can be appreciated that the ongoing rise in the air's CO2 concentration should help the cork oak species to better deal with those stresses, if they actually do occur.

Reviewed 25 April 2007