Background
The authors write that the cordgrass Spartina maritima "is an important pioneer and ecosystem engineer in salt marshes on the Atlantic coast of southern Europe," citing Castellanos et al. (1994); and they say that "using the C4 pathway," this halophyte "produces extensive stands in a range of marsh environments," citing Castellanos et al. (1998).

What was done
Working with 15-cm-diameter clumps of S. maritima that they obtained from a low-marsh site along the southwest coast of Spain in April of 2007, which they transplanted into individual plastic pots filled with pearlite that rested on shallow trays filled with Hoagland's solution of three different salinities (0, 170 or 510 mM NaCl), Mateos-Naranjo et al. maintained the plants in controlled environment chambers having atmospheric CO2 concentrations of either 380 ppm or 700 ppm (an increase of 84%) for periods of 30 days, during which time they measured a number of plant properties and processes.

What was learned
The four researchers report that the 84% increase in the atmosphere's CO2 concentration stimulated the growth of S. maritima by about 65% in all three salinity treatments, while the graphical representation of the halophyte's water use efficiency indicates that this important property of the plant was enhanced by approximately 10%, 100% and 160% in the 0, 170 and 510 mM salinity treatments, respectively, due to the fact that "increasing CO2 concentration has a positive effect on the photochemical apparatus, helping to counteract salt stress experienced by plants at current CO2 concentrations."

What it means
The UK and Spanish scientists say their results suggest that the productivity of S. maritima "might increase in a future scenario of rising atmospheric CO2 concentration in environments with salinities as high as that of seawater," which is extremely good news for what they describe as "an important pioneer and ecosystem engineer in salt marshes."

References
Castellanos, E.M., Figueroa, M.E. and Davy, A.J. 1994. Nucleation and facilitation in saltmarsh succession: interactions between Spartina maritima and Arthrocnemum perenne. Journal of Ecology 82: 239-248.

Castellanos, E.M., Heredia, C., Figueroa, M.E. and Davy, A.J. 1998. Tiller dynamics of Spartina maritima in successional and non-successional Mediterranean salt marsh. Plant Ecology 137: 213-225.