How does rising atmospheric CO2 affect marine organisms?

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Effects of Elevated CO2 on Tree Vulnerability to Embolism
Gartner, B.L., Roy, J. and Huc, R.  2003.  Effects of tension wood on specific conductivity and vulnerability to embolism of Quercus ilex seedlings grown at two atmospheric CO2 concentrations.  Tree Physiology 23: 387-395.

What was done
Knowing that "plants grown in elevated CO2 should require less water for the same carbon gain than plants grown in ambient CO2," the authors hypothesized that CO2-enriched plants could produce wood with a lower capacity for water flux, i.e., with a lower kS or specific conductivity, and that they "could have wood that is more vulnerable to embolism because a disabled set of vessels would have a lower impact on a plant with a lower need for water transport than on a plant that has a higher need."  Hence, they investigated these hypotheses with Quercus ilex seedlings that had been grown for over a year in climate-controlled greenhouses in either ambient air or air enriched to twice the ambient concentration of CO2.

What was learned
Contrary to what they had initially thought might be the case, the authors report that "plants grown in elevated CO2 did not differ significantly in vulnerability to embolism or kS from plants grown in ambient CO2."  They also report that "Tognetti et al. (1999) found no significant effect of elevated CO2 on vulnerability to embolism or kS of branch samples from Q. ilix trees growing near CO2 vents compared with trees growing at normal ambient CO2."

What it means
On the basis of these two studies, it would appear that atmospheric CO2 enrichment does not produce any negative or deleterious effects on water transport in either young or mature Q. ilix trees.  Hence, there should be little to interference with their obtaining the many benefits of elevated CO2 that are expected to accompany the ongoing rise in the air's CO2 content [see Long-Term Studies (Woody Plants - Oak Trees) in our Subject Index].

Tognetti, R., Longobucco, A. and Raschi, A.  1999.  Seasonal embolism and xylem vulnerability in deciduous evergreen Mediterranean trees influenced by proximity to a carbon dioxide spring.  Tree Physiology 19: 271-277.

Reviewed 9 July 2003