How does rising atmospheric CO2 affect marine organisms?

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Elevated CO2 Stimulates Cell Division in Dactylis glomerata
Kinsman, E.A., Lewis, C., Davies, M.S., Young, J.E., Francis, D., Vilhar, B. and Ougham, H.J.  1997.  Elevated CO2 stimulates cells to divide in grass meristems: a differential effect in two natural populations of Dactylis glomerataPlant, Cell and Environment 20: 1309-1316.

What was done
The authors grew specimens of the grass Dactylis glomerata collected from two locations (Portugal and Sweden) for about two months in open-top chambers receiving atmospheric CO2 concentrations of 400 and 700 ppm to study the effects of elevated CO2 on their meristematic cell division.

What was learned
Elevated CO2 shortened the cell cycle by about 25% in shoot meristems from both geographic locations.  In addition, elevated CO2 increased the proportion of rapidly dividing cells in shoot apical meristems.  However, this CO2-induced stimulation was much greater for plants from the Portuguese source than it was for plants from the Swedish source (1.5-fold to 3-fold vs. 1.2-fold, respectively), probably as a consequence of the warmer growth temperatures characteristic of Portugal vs. Sweden.

With respect to root meristems, atmospheric CO2 enrichment shortened the cell cycle by 17 and 8% for plants from Portuguese and Swedish sources, respectively.  In addition, elevated CO2 increased the proportion of rapidly dividing cells in root apical meristems by 86 and 31% for plants from these same sources.

It would thus appear that elevated CO2 not only speeds up the cell cycle in the meristems of this grass species, but that it increases the proportion of meristematic cells that are rapidly dividing.  This phenomenon results in increased growth rates and can lead to greater biomass production.  Indeed, the authors reported that the greater CO2-induced stimulation of cell division in plants from the Portuguese source led to a 33% enhancement in their dry weight, compared to a slightly smaller 21% enhancement for plants from the Swedish source.

What it means
As the CO2 content of the air rises, it is likely that Dactylis glomerata will increase its cell division and growth rates the world over in a temperature-dependent manner, with the greatest percentage stimulations occurring in its warmer temperature ranges.  Thus, this phenomenon should maintain the genetic diversity that exists within this species, populations of which are spread out across the globe.

Reviewed 1 April 2000