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The Effect of Ocean Acidification on the Growth Rates of Diatoms

Paper Reviewed
Wu, Y., Campbell, D.A., Irwin, A.J., Suggett, D.J. and Finkel, Z.V. 2014. Ocean acidification enhances the growth rate of larger diatoms. Limnology and Oceanography 59: 1027-1034.

In a study published in Limnology and Oceanography, Wu et al. (2014) write that "ocean acidification is changing the nature of inorganic carbon availability in the global oceans." And since diatoms are responsible for approximately 40% of all marine primary production, they felt it important to determine, in this regard, if the larger of these important calcifiers was being helped or hurt by this phenomenon, and whether their size was a factor in determining either its sign or magnitude.

In exploring these questions in the laboratory, the five scientists quantified various effects of the partial pressure of seawater CO2 at levels of 190, 380 and 750 µL/L on growth rate, photosystem II electron transport rate (ETR), and elemental composition for five diatom species ranging over five orders of magnitude in the size of their cells. And what did they thereby learn?

Wu et al. determined that the growth rates of five different diatom species were enhanced in seawater of 740 µL/L CO2 concentration relative to growth rates observed in seawater of 190 and 380 µL/L of CO2, with little concomitant change in ETR or elemental stoichiometries, while the different diatom species all enhanced their allocation of photochemical energy to growth under the two elevated PCO2 concentrations. More specifically, they report that under 750 vs 190 µL/L partial pressure of CO2, "growth rate was enhanced by ~5% for the smaller diatom species to ~30% for the largest species examined."

In the concluding paragraph of their paper, Wu et al. thus indicate that their results suggest "future increases in CO2 would favor increased growth rates of larger diatoms, especially in productive regions, which may act to increase the rate and efficiency of carbon export from the surface to the deep sea." And this phenomenon, in turn, would obviously help to slow the rate-of-rise of the atmosphere's CO2 concentration, which is the ultimate goal of the world's climate alarmists, which facts further highlight the greater fact that nature itself can take care of itself, without a bit of "help" from global regulators, as a detailed search of our website reveals a number of different ways by which a number of natural phenomena can accomplish this very task, while doing it all by themselves (see the subheadings under Feedback Factors here.

Posted 25 March 2015