How does rising atmospheric CO2 affect marine organisms?

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Response of a Nutrient-Poor Low-Productivity Calcareous Grassland to Atmospheric CO2 Enrichment
Thurig, B., Korner, C. and Stocklin, J.  2003.  Seed production and seed quality in a calcareous grassland in elevated CO2Global Change Biology 9: 873-884.

What was done
After five years of exposure of a nutrient-poor low-productivity calcareous grassland to atmospheric CO2 concentrations of 360 and 660 ppm that was conducted in the northwestern part of Switzerland via "a novel CO2-enrichment technology" -- screen-aided CO2 control (SACC; Leadley et al., 1997) -- the authors measured the vegetative and reproductive responses of the various types of plants that comprised the ecosystem.

What was learned
It was determined that "the effect of elevated CO2 on the number of flowering shoots (+24%, P less than 0.01) and seeds (+29%, P = 0.06) at the community level was similar to above ground biomass response."  In terms of functional groups of species, there was a 42% (P less than 0.01) increase in the mean seed number of graminoids and a 33% (P = 0.07) increase in the mean seed number of forbs, but no change in legumes in this regard.  In most species, mean seed weight also tended to be greater (+12%, P less than 0.01).

What it means
Even in what the authors describe as a nutrient-poor, low-productivity calcareous grassland, atmospheric CO2 enrichment significantly increased both vegetative and reproductive biomass production.  In addition, they say it is known from many studies that heavier seeds result in seedlings that "are more robust than seedlings from lighter seeds (Baskin and Baskin, 1998)."  Hence, the continued rising of the air's CO2 content would appear to bode well for these nutrient-poor Swiss grasslands, as well as for other low-productivity grasslands around the world.

Baskin, C.C. and Baskin, J.M.  1998.  Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination.  Academic Press, San Diego, CA.

Leadley, P.W., Niklaus, P.A., Stocker, R. et al.  1997.  Screen-aided CO2 control (SACC): a middle ground between FACE and open-top chambers.  Acta Oecologica 18: 39-49.

Reviewed 29 October 2003