The Canadian researchers, Moazami-Goudarzi and Colman, found in a study of two green marine algae that there were no significant differences in growth rates over a range of reduced pH values. From Journal of Experimental Marine Biology and Ecology - (LINK)
From pre-industrial times to the present, the atmosphere's CO2 concentration has risen well in excess of 100 ppm, leading to a drop of 0.1 pH unit in earth's seawater, while anticipated CO2 increases to the end of the current century are suggestive of a further drop of 0.3-0.5 pH unit, according to Caldeira and Wickett (2003, 2005). So what do these projections portend for the productivity of the world's marine algae?
What was done
In a study of two such green marine algae (Stichococcus cylindricus and Stichococcus minor), Moazami-Goudarzi and Colman measured their growth rates while growing them in artificial seawater - as per Berges et al. (2001) - within 125-ml Erlenmeyer flasks at pH values of 5.0, 6.0, 7.0, 8.2, 9.0 and 9.5, as well as at a variety of salinity levels (25, 50, 100, 200 and 470 mM).
What it means
With Moazami-Goudarzi and Colman determining that S. minor and S. cylindricus "were able to tolerate a broad range of pH from pH 5.0 to 9.5," as well as the broad range of salinities they investigated, it would appear that even the worst nightmare of the world's climate alarmists would not be a great impediment to the continued wellbeing of these two green marine algae, even without the positive influence of evolutionary forces that would likely come into play over the timespan involved in the seawater transformations envisioned by Caldeira and Wickett.
Moazami-Goudarzi, M. and Colman, B. 2012. Changes in carbon uptake mechanisms in two green marine algae by reduced seawater pH. Journal of Experimental Marine Biology and Ecology 413: 94-99.