How does rising atmospheric CO2 affect marine organisms?

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Effects of Elevated CO2 in a Maturing Scrub-Oak Ecosystem
Ainsworth, E.A., Davey, P.A., Hymus, G.J., Drake, B.G. and Long, S.P.  2002.  Long-term response of photosynthesis to elevated carbon dioxide in a Florida scrub-oak ecosystem.  Ecological Applications 12: 1267-1275.

What was done
After burning a scrub-oak ecosystem (dominated by Quercus myrtifolia, Q. chapmanii, and Q. geminata) in Florida, USA, to the ground, the authors erected open-top chambers on the site and fumigated them with air containing CO2 concentrations of approximately 380 and 700 ppm to study the effects of elevated CO2 on community regeneration.  This paper reports the photosynthetic responses of the three dominant perennial species during canopy closure, which occurred during the third and fourth years of the study.

What was learned
Regardless of season or study year, elevated CO2 consistently increased photosynthetic rates in Q. myrtifolia and Q. chapmanii by as much as 150% without inducing any degree of photosynthetic acclimation.  In contrast, atmospheric CO2 enrichment did not cause persistent photosynthetic increases in Q. geminata, which displayed significant signs of photosynthetic acclimation to elevated CO2.  Nevertheless, after three years of exposure to elevated CO2, all three oak species exhibited an average increase in their rates of photosynthesis of 53%, which translated into significant increases in biomass production for Q. myrtifolia and Q. chapmanii, but not Q. geminata.

What it means
As the CO2 content of the air continues to rise, regenerating scrub-oak communities will likely exhibit enhanced rates of photosynthesis that will persist throughout canopy closure and maturity.  Moreover, these increases in photosynthesis will likely enhance biomass production in these communities.  Indeed, the authors concluded that "sustained increases in Asat exhibited by Q. myrtifolia and Q. chapmanii have translated to increased growth in these species, and there is no suggestion that this trend is changing."  Thus, carbon sequestration in regenerating and maturing scrub-oak ecosystems is likely to increase with future increases in the air's CO2 concentration.

Reviewed 12 February 2003