How does rising atmospheric CO2 affect marine organisms?

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Ocean Acidification, Marine Food Production, and Calcification
Volume 15, Number 43: 24 October 2012

Diatoms are a type of algae, most of which are unicellular, that serve as primary producers in various marine food chains; and, therefore, it is critically important to know how they may respond to continued increases in the air's CO2 content, especially since they are responsible for about 40% of current marine primary productivity (Field et al., 1998). Likewise, it is also important to know how other unicellular algae called coccolithophores will respond to rising CO2 concentrations, since they are globally-distributed phytoplankton that are major marine calcifiers, the calcium carbonate scales of which sink to the bottom of the sea upon their deaths, where the carbon they contain is sequestered far away from the atmosphere. And it just so happens that a recent study published in the Journal of Phycology by McCarthy et al. (2012) examines both of these groups of microalgae within the context of CO2-induced ocean acidification, which climate alarmists claim will spell the ruin of both marine food production and marine carbon storage.

In describing their approach to analyzing this potential problem, the team of four Canadian researchers from Mount Allison University in Sackville, New Brunswick, say they grew the coccolithophore Emiliania huxleyi and two strains of the diatom Thalassiosira pseudonana under low light in turbidostat photobioreactors bubbled with air containing either 390 ppm or 750 ppm CO2, finding that "increased CO2 led to increased growth rates in all three strains" and that "CO2 thus had a fertilization effect on all species, enhancing growth rates 20%-40%." They also report that "total cellular protein did not change between ambient and 750 ppm CO2 treatments," but that "cellular RUBISCO content showed a 2- to 3-fold increase with [elevated] CO2 in both E. huxleyi and in the coastal diatom strain."

In commenting on their observations, McCarthy et al. write that the CO2 "fertilization effect on the growth rates of T. pseudonana and E. huxleyi ... observed at low light and nutrient repletion imparts these species with increased competitive ability under these conditions," which are characteristic of coastal ocean zones. And they thus conclude - in diametrical contradiction of the fears of climate alarmists - that their results suggest that "there could be a net increase in capacity for primary productivity at 750 ppm CO2, at least with regard to small diatoms and coccolithophores in coastal environments," where the two types of phytoplankton provide the bulk of current marine primary productivity.

Sherwood, Keith and Craig Idso

Field, C.B., Behrenfeld, M.J., Randerson, J.T. and Falkowski, P. 1998. Primary production of the biosphere: integrating terrestrial and oceanic components. Science 281: 137-140.

McCarthy, A., Rogers, S.P., Duffy, S.J. and Campbell, D.A. 2012. Elevated carbon dioxide differentially alters the photophysiology of Thalassiosira pseudonana (Bacillariophyceae) and Emiliania huxleyi (Haptophyta). Journal of Phycology 48: 635-646.