How does rising atmospheric CO2 affect marine organisms?

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An Inulin-Producing Asteraceae from the Brazilian Cerrado
Oliveira, V.F., Zaidan, L.B.P., Braga, M.R., Aidar, M.P.M. and Carvalho, M.A.M. 2010. Elevated CO2 atmosphere promotes plant growth and inulin production in the cerrado species Vernonia herbacea. Functional Plant Biology 37: 223-231.

The authors write that "presently, there is a growing interest in the use of inulin as a health food ingredient, as an alternative for low-calorie sweeteners, and as a dietary fiber and fat substitute (Ritsema and Smeekens, 2003)." In addition, they say "it is suggested" that a daily intake of low amounts of inulin or its derivatives generate certain bifidogenic effects that promote the growth of beneficial bacteria in the intestinal tract, as well as anti-tumor effects, citing the writings of Roberfroid (2005). And they state that Vernonia herbacea (Vell.) Rusby is an Asteraceae from the Brazilian Cerrado that accumulates inulin-type fructans in certain underground organs called rhizophores.

What was done
Well watered and fertilized V. herbacea plants were grown from rhizophore fragments for two months and then transferred -- in groups of three -- to 3-L pots containing forest soil, after which they were maintained in open-top chambers within a glasshouse for 120 days at atmospheric CO2 concentrations of either 380 pr 760 ppm, during which period Oliveira et al. measured plant net photosynthetic rates, water use efficiencies and fructan concentrations after 15, 30, 60, 90 and 120 days of treatment, as well as above- and below-ground biomass at the end of the experiment.

What was learned
The five Brazilian researchers report that "plants under elevated CO2 presented increases in height (40%), photosynthesis (63%) and biomass of aerial (32%) and underground (47%) organs when compared with control plants." In addition, they state that "water use efficiency was significantly higher in treated plants, presenting a 177% increase at day 60." Last of all, they report that fructan concentration remained unchanged; but because of the significant CO2-induced increase in underground organ biomass, they write that "a 24% increase in total fructan yield occurred."

What it means
Because of the significant enhancement of inulin-type fructan production by V. herbacea under conditions of atmospheric CO2 enrichment, the positive health effects of those compounds, and the great increase in water use efficiency displayed by the plants while producing them, a CO2-enriched future would appear to bode well for their commercial production throughout much of the central fifth -- the Cerrado -- of Brazil.

Ritsema, T. and Smeekens, S. 2003. Fructans: beneficial for plants and humans. Current Opinion in Plant Biology 6: 223-230.

Roberfroid, M.B. 2005. Introducing inulin-type fructans. British Journal of Nutrition 93: S13-S25.

Reviewed 11 August 2010