How does rising atmospheric CO2 affect marine organisms?

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Antarctic Moss Responses to Atmospheric CO2 Enrichment
Pannewitz, S., Green, T.G.A., Maysek, K., Schlensog, M., Seppelt, R., Sancho, L.G., Turk, R. and Schroeter, B. 2005. Photosynthetic responses of three common mosses from continental Antarctica. Antarctic Science 17: 341-352.

What was done
Working with Bryum subrotundifolium, a "widely distributed moss found on banks and disturbed soils in moist or wet sites in continental Antarctica," and B. pseudotriquetrum, which "grows as a dense turf in moist or wet places along meltwater channels and in low lying flush areas," the authors determined their short-term photosynthetic responses to as much as a 5.5-fold increase in the atmosphere's CO2 concentration (a multi-step increase from ~360 ppm to ~2000 ppm) at various light intensities and air temperatures.

What was learned
According to Pannewitz et al., net photosynthesis of both moss species "showed a large response to increase in CO2 concentration and this rose with increase in temperature." In the case of B. subrotundifolium, net photosynthesis saturated (maxed out) above ~1000 ppm CO2, but B. pseudotriquetrum "showed no saturation up to 2000 ppm, particularly at 20C," which was the highest temperature they studied. More specifically, they report that "when measured at an increased CO2 level of 2000 ppm, net photosynthetic rates for B. subrotundifolium were 60-80% higher than at the accepted ambient level of 360 ppm and net photosynthesis of B. pseudotriquetrum was more than doubled."

What it means
In the final sentence of their report, the scientists comprising the international research team - which hailed from Australia, Austria, Germany, Israel, New Zealand and Spain - say that "the photosynthetic rates of both Bryum species were certainly increased by experimentally generated elevated CO2," which bodes well indeed for these important pioneer plants, especially if the air's CO2 content continues to climb. It would thus appear that even small parts of continental Antarctica may be participating in the ongoing and truly global greening of the earth.

Reviewed 25 July 2007