Background
"Marine phytoplankton contribute approximately 50% of the total global primary productivity and play a vital role in global carbon cycling," according to Beardall et al. (2009); and they say "it is extremely important to understand the impact that global climate change will have on the ecological performance of these organisms," which is precisely what Berge et al. do with respect to the effects of atmospheric CO2 enrichment on seawater pH and its impact on phytoplankton growth rates.

What was done
Using the acid (HCl) addition method to lower seawater pH, the authors assessed how growth and production rates were affected in "the most common coastal marine phytoplankton groups (diatoms, dinoflagellates, prymnesiophytes, and cryptophytes)." This they did via experiments conducted in the laboratory with the plankton enclosed within 270-ml sterile polycarbonate bottles that were filled to capacity to avoid gas exchange with the air. Representing diatoms in these experiments was Coscinodiscus granii; representing prymnesiophytes was Prymnesium parvum; representing cryptophytes were Rhodomonas marina and Teleaulax amphioxeia; while representing dinoflagellates were Prorocentrum minimum, Prorocentrum micans, Karlodinium veneficum and Heterocapsa triquetra.

What was learned
Berge et al. write that "our results and literature reports on growth at lowered pH indicate that marine phytoplankton in general are resistant to climate change in terms of ocean acidification, and do not increase or decrease their growth rates according to ecological relevant ranges of pH and free CO2."

What it means
This finding is very similar to what has been obtained by the great majority of other studies of the ocean acidification phenomenon -- not just with phytoplankton, but with all types of marine organisms -- as may be seen by perusing the wealth of information we have assembled in our Ocean Acidification Database. Hence, the angst that has been created by climate alarmists over this issue would appear to have little to do with reality.

Reference
Beardall, J., Stojkovic, S. and Larsen, S. 2009. Living in a high CO2 world: impacts of global climate change on marine phytoplankton. Plant Ecology and Diversity 2: 191-205.