Ocean Acidification and Marine Diatoms
Wu, Y., Gao, K. and Riebesell, U. 2010. CO2-induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum. Biogeosciences 7: 2915-2923.
In further exploration of this phenomenon, Wu et al. cultured the diatom Phaeodactylum tricornutum -- which had been isolated from the South China Sea -- for at least 20 generations in artificial seawater equilibrated with air of either 388 or 1000 ppm CO2, which resulted in water pH values of either 8.15 or 7.80, respectively, while they measured the diatom's photosynthetic carbon fixation, dark respiration and growth rates.
The three researchers report that photosynthetic carbon fixation was enhanced by 12% under the high CO2 and low pH conditions. However, since dark respiration was also enhanced, the daily net photosynthetic production was stimulated by a lesser 5.8%; and this value, as they describe it, "closely agreed with the observed increase in growth," which they had independently determined to have been enhanced by 5.2% under the high CO2 and low pH conditions.
With respect to the implications of their findings, Wu et al. write that if "the roughly 5% increase in the growth of diatoms were taken into account based on the values obtained in this study, this would allow diatoms to rapidly accumulate more biomass (by about 34% in 6 days) and drawdown available nitrogen and other nutrients, leading to a greater biological carbon flux to the deep sea." And because diatoms contribute "about half of the marine primary production," in their words, this phenomenon would provide a significant brake on the rate-of-rise of the atmosphere's CO2 concentration and its ability to cause global warming.
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