Compilation of Acidification Experiments
(modified from supplemental material associated with Dutkiewicz et al., submitted 2015)

In order to develop a baseline understanding of the responses of phytoplankton groups to ocean acidification, we conducted a comprehensive literature search of laboratory studies (current as of December 2014). We focused on growth rate effects, but additional data were recorded as well. A search of the Web of Science was conducted using the search phrase "(coccolith* OR diatom* OR prochloroc* OR synechoc* OR trichodes* OR crocosphae* OR diazotroph*) AND (CO₂ OR "carbon dioxide" OR "ocean acidification") AND ("growth rate")". Each abstract was read and any paper that mentioned a comparison between ambient and elevated CO₂ conditions was downloaded. Additional papers were selected based on reference lists from the above papers and personal communications with researchers. We further curated these papers by excluding any that i) did not actually compare growth rates at different CO₂ concentrations, ii) did not specify the CO₂ levels examined, iii) used CO₂ concentrations outside the range 250 – 1100 ppmv, iv) attempted to separately manipulate CO₂ concentration and pH using organic buffers, v) manipulated CO₂/pH in such a way as to radically change alkalinity, and/or vi) presented data in such a way that it was impossible to calculate a ratio of elevated:ambient growth rates. One additional paper was removed because it had been retracted. We also did not consider comparisons of growth rates for organisms in mixed communities or for freshwater species.

Table 1 (PDF) shows the papers that were used for the meta-analysis, and Table 2 (PDF)shows the papers that were rejected along with the reasons for rejection. Values were collected from tabulated data in papers where possible; otherwise values were estimated visually from figures. No attempt was made to extract information about replication level, variance, or significance level of data; only experimental means were collected. Many papers examined the response to CO₂ enrichment under a variety of environmental conditions (e.g., different light or nutrient levels). Each environment was considered as a unique experiment, and no attempt was made to examine covariance or synergy between any other parameter and response to CO₂.

All data points in the dataset represent ratios of the value in a high CO₂ experiment to the value in an ambient CO₂ environment.