How does rising atmospheric CO2 affect marine organisms?

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Elevated CO2 Stimulates Soil Microbial Activities Beneath a Calcareous Grassland
Arnone, J.A., III and Bohlen, P.J.  1998.  Stimulated N2O flux from intact grassland monoliths after two growing seasons under elevated atmospheric CO2Oecologia 116: 331-335.

What was done
The authors grew intact grass monoliths removed from a species-rich calcareous grassland in northwestern Switzerland and exposed them to atmospheric CO2 concentrations of 350 and 600 ppm for two full growing seasons to study the effects of elevated CO2 on various ecosystem processes.

What was learned
Monoliths exposed to elevated CO2 exhibited soil moisture contents that were 10 to 20% greater than those exposed to ambient CO2 concentrations, most likely due to reductions in transpirational water loss facilitated by CO2-induced decreases in vegetative stomatal conductance.  In turn, soil heterotrophic activity nearly doubled with increasing soil moisture.  Thus, soil microbial activities were about twice as great in CO2-enriched monoliths than they were in ambiently-grown monoliths.

What it means
As the CO2 content of the air rises, it is likely that calcareous grasslands will increase the amount of soil moisture they contain.  With greater soil moisture contents, it is likely that microbial activities will increase in such soils, including those that mineralize inorganic nutrients making them available for plant usage.  Thus, this chain of events should further stimulate plant growth in these ecosystems by enhancing the growth response resulting from the aerial fertilization effect of increasing atmospheric CO2 concentrations.

Reviewed 1 April 2000