How does rising atmospheric CO2 affect marine organisms?

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Effects of Elevated CO2 and Temperature on Ponderosa Pine
Maherali, H. and DeLucia, E.H. 2000. Interactive effects of elevated CO2 and temperature on water transport in ponderosa pine. American Journal of Botany 87: 243-249.

What was done
Ponderosa pine (Pinus ponderosa) seedlings were grown for six months in controlled environment chambers receiving atmospheric CO2 concentrations ranging from 350 to 1100 ppm. In addition, seedlings at each CO2 concentration were subjected to low (15/25C night/day) and high (20/30C night/day) temperature treatments to determine the interactive effects of elevated CO2 and temperature on growth in this important timber species.

What was learned
Although elevated CO2 had no significant effect on stomatal conductance in this species, seedlings grown at high temperature exhibited a 15% increase in this parameter relative to seedlings grown at the low temperature regime. Similarly, specific hydraulic conductivity, which is a measure of the amount of water moving through a plant relative to its leaf area, also increased in seedlings exposed to the high temperature treatment, without being affected by elevated CO2. However, atmospheric CO2 enrichment did influence biomass production in both temperature regimes. Seedling biomass, for example, increased by 42% in the low temperature treatment when the atmospheric CO2 content was raised from 350 to 1100 ppm and by 62% in the high temperature treatment over the same CO2 concentration interval. Thus, seedling biomass increased with increasing CO2 concentration; and this phenomenon was greatest in the higher, rather than in the lower, temperature treatment.

What it means
As the atmospheric CO2 concentration continues to increase, it is likely that ponderosa pine seedlings will exhibit enhanced biomass production, regardless of air temperature. In fact, if air temperatures rise in the future, regardless of the cause, ponderosa pine seedlings should grow even better than they do at lower air temperatures due to the strong positive interaction that exists between elevated CO2 and temperature for this species.

Reviewed 15 July 2000