How does rising atmospheric CO2 affect marine organisms?

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Growth Response of Arabidopsis thaliana to Elevated CO2
Gibeaut, D.M., Cramer, G.R. and Seemann, J.R. 2001. Growth, cell walls, and UDP-glucose dehydrogenase activity of Arabidopsis thaliana grown in elevated carbon dioxide.  Journal of Plant Physiology 158: 569-576.

What was done
The authors grew the common weed Arabidopsis thaliana for seven weeks in controlled environments receiving atmospheric CO2 concentrations of 360 and 1000 ppm to study the effects of elevated CO2 on growth in this model plant species.

What was learned
The 640-ppm increase in the air's CO2 concentration increased the relative growth rate of the plants by about 20% during the first three weeks of the study.  Thereafter, however, the relative growth rate was the same in both treatments.  Nonetheless, by the end of the study the CO2-enriched plants had produced 2.3 times more biomass than the ambiently-grown plants.  Interestingly, the increase in CO2 increased the activity of the enzyme UDP-glucose dehydrogenase - which is a key enzyme involved in cell wall biosynthesis - by approximately 25% during the first three weeks of the study, when the CO2-enriched plants maintained a 20% relative growth rate advantage over the ambiently-grown plants.

What it means
As the atmospheric CO2 concentration increases, Arabidopsis thaliana will likely display increased relative growth rates that should allow them to produce biomass faster than they currently do under ambient CO2 concentrations.  This phenomenon is likely facilitated by the concomitantly enhanced activity of UDP-glucose dehydrogenase, which stimulates the formation of new cells and thereby allows more biomass to be produced.

Reviewed 2 October 2002