How does rising atmospheric CO2 affect marine organisms?

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Helping Halophytes Combat Soil Salinization
Geissler, N., Hussin, S. and Koyro, H.-W. 2009. Elevated atmospheric CO2 concentration ameliorates effects of NaCl salinity on photosynthesis and leaf structure of Aster tripolium L. Journal of Experimental Botany 60: 137-151.

The authors write that "desertification is often accompanied by soil salinization ... leading to growth conditions inacceptable for most conventional crops." However, they note that what they call "a promising solution" to the problem "is the desalinization and reclamation of degraded land by making sustainable use of naturally salt-tolerant halophytes under seawater irrigation (including drainage mechanisms which avoid salt accumulation in the soil)." What is more, they indicate that the leaves of certain halophytes "have a high nutritional value and can be eaten as salad or vegetable," making them "a promising potential cash crop."

What was done
In a study germane to both of these functions -- land reclamation and edible biomass production -- Geissler et al. grew well-fertilized two-month-old Aster tripolium L. plants for one additional month in a hydroponics system maintained at seawater salinity (sws) levels of 0, 50 and 100% within open-top chambers in northern Germany that were maintained at atmospheric CO2 concentrations of either 380 ppm (ambient) or 520 ppm (elevated), during which time they measured several plant properties and processes.

What was learned
In ambient air, the three researchers found that growing the plants with water of 100% sws (as opposed to 0% sws) resulted in "a significant decrease in photosynthesis [65%] and water use efficiency [33%] and to an increase in oxidative stress." But when the air's CO2 concentration was raised by 37% (from 380 to 520 ppm), there was a subsequent increase of 84% in photosynthesis and 60% in water use efficiency. In addition, they determined that "the improved water and energy supply was used to increase the investment in mechanisms reducing water loss and oxidative stress."

What it means
In concluding their paper, Geissler et al. say that because "elevated CO2 concentration enhances the energy and water supply of Aster tripolium, ameliorates oxidative stress, and thus enhances the survival of this plant in saline habitats," it (1) "seems to be a promising cash crop halophyte for a future with rising atmospheric CO2 concentrations," and (2) "can help in desalinizing and reclaiming degraded land and sequestering CO2, thus counteracting the greenhouse effect."

Reviewed 13 May 2009