How does rising atmospheric CO2 affect marine organisms?

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Effects of CO2 on Microbial Community Structure
Griffiths, B.S., Ritz, K., Ebblewhite, N., Paterson, E. and Killham, K.  1998.  Ryegrass rhizosphere microbial community structure under elevated carbon dioxide concentrations, with observations on wheat rhizosphere.  Soil Biology and Biochemistry 30: 315-321.

What was done
Ryegrass microcosms were placed in growth cabinets with atmospheric CO2 concentrations of 450 or 720 ppm for approximately six weeks to study the effects of elevated CO2 on ryegrass rhizosphere microbial community structure.  Similarly, wheat microcosms were placed in glasshouses with atmospheric CO2 concentrations of 350 or 700 ppm for 18 weeks to study this same phenomenon.  In addition, some of the ryegrass microcosms were exposed to radioactive 14CO2, in order to determine the allocation of fixed carbon within them.

What was learned
Elevated atmospheric CO2 concentrations did not affect rhizosphere microbial community structures of ryegrass or wheat, nor did it affect the proportion of fixed carbon allocated to microbial biomass.  It did, however, increase the amount of non-microbial rhizosphere carbon more than 2.6-fold.

What it means
The results of this research suggest that, as the CO2 content of the air continues to rise, rhizosphere microbial community structures for ryegrass and wheat will remain unchanged, thus maintaining soil microbial biodiversity beneath these plants.  They also suggest that with more CO2 in the air, greater amounts of fixed carbon can be stored in the rhizosphere beneath ryegrass, thereby enhancing the terrestrial biosphere's carbon sink capacity.

Reviewed 15 January 1999