How does rising atmospheric CO2 affect marine organisms?

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Elevated CO2 Stimulates Photosynthesis at Low Temperatures
Reference
Bunce, J.A. 2000. Acclimation to temperature of the response of photosynthesis to increased carbon dioxide concentration in Taraxacum officinale. Photosynthesis Research 64: 89-94.

What was done
The author measured photosynthetic rates in field-grown Taraxacum officinale plants at different temperatures (15 to 34C) and atmospheric CO2 concentrations (350 to 525 ppm) to determine if CO2-induced increases in photosynthesis are influenced by air temperature. Different air temperatures were achieved by simply measuring photosynthetic rates at different times throughout the year, while different CO2 concentrations were achieved by increasing the amount of CO2 within the measurement cuvette of the portable gas exchange analyzer.

What was learned
Photosynthetic rates measured at an atmospheric CO2 concentration of 525 ppm were 10 to 30% higher than what is predicted by current biochemical models of photosynthesis at air temperatures between 15 and 25C.

What it means
As the atmospheric CO2 concentration continues to rise, it is likely that this plant species, and possibly others, will exhibit larger-than-predicted CO2-induced increases in photosynthetic rates. Indeed, the author's final sentence states that "it is premature to conclude that the relative stimulation of photosynthesis by rising atmospheric [CO2] will necessarily be less in cool climates or at cool times of the year," as many plant scientists, including we, have long believed. If this conclusion holds up under further scrutiny, the productivity of the totality of earth's vegetation may be even more stimulated by atmospheric CO2 enrichment than has been anticipated by many of its most ardent advocates, due to possibly larger-than-expected CO2-induced increases in photosynthesis at low air temperatures.