How does rising atmospheric CO2 affect marine organisms?

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Net Ecosystem CO2 Exchange in a Post-Fire Regenerating Scrub-Oak Ecosystem In a CO2-Enriched Atmosphere
Hymus, G.J., Johnson, D.P., Dore, S., Anderson, H.P., Hinkle, C.R. and Drake, B.G.  2003.  Effects of elevated atmospheric CO2 on net ecosystem CO2 exchange of a scrub-oak ecosystem.  Global Change Biology 9: 1802-1812.

What was done
The authors studied net ecosystem exchange (NEE) of CO2 in a scrub-oak ecosystem - 85-90% of the aboveground biomass of which is comprised of three oak species (Quercus myrtifolia, Quercus geminata and Quercus chapmanii) - on Merritt Island within NASA's Kennedy Space Center on the coast of central Florida.  This ecosystem was completely burned in January of 1996, after which sixteen open-top chambers (OTCs) were established upon it in the spring of that year, half maintained at the ambient atmospheric CO2 concentration and half maintained at ambient plus 350 ppm.  Measurements were begun in June 1999 and continued for 25 months through July 2001.

What was learned
Hymus et al. report that throughout their study, the extra CO2 supplied to the CO2-enriched OTCs "increased maximum NEE and the apparent quantum yield of the NEE during the photoperiod," noting further that the magnitude of the stimulation of maximum NEE, expressed per unit ground area, "was seasonal, rising from 50% in the winter to 180% in the summer," in accord with what is known about the interactive effects of atmospheric CO2 enrichment and daily, seasonal and multi-year warming [see Growth Response to CO2 With Other Variables (Temperature) in our Subject Index].  Hence, they conclude that "during this two-year period more carbon was sequestered at elevated CO2 in this ecosystem."

What it means
The authors say their study "constitutes the largest data set showing the effects of elevated CO2 on NEE measured in situ, and is the first to be carried out in a woody ecosystem," with the beneficial effects of atmospheric CO2 enrichment "still evident after 6 years regeneration in the elevated CO2."  In addition, they report that "in the marsh ecosystem of the Chesapeake Bay, an increased ecosystem carbon uptake in the elevated CO2 has been observed for 16 years."  Hence, the experimentally-observed near-universal positive responses of almost all plants to increases in the air's CO2 content will likely be maintained indefinitely in our world of rising atmospheric CO2 concentrations, as is likewise suggested by the many other studies of this subject that we have reviewed and listed under the heading of Long-Term Studies in our Subject Index.

Reviewed 18 February 2004