Methodology:

Calcification was estimated by measuring the change in buoyant weight (Davies 1989) based on an initial measurement of all the corals and subsequent measures on one-third of the corals after 1, 2, and 3 weeks of incubation in order to monitor the evolution of the treatment effects through time. The difference between initial and final buoyant weight was converted to dry weight increments using an aragonite density of 2.93 g cm-3 (Davies 1989) and standardized to the area of the corals as determined by the aluminum foil technique (Marsh 1970). Dry tissue weight of the organisms also was measured to normalize calcification to biomass to evaluate changes in biomass that might result from changes in the size of energy reserves attributed to the feeding regimes. To determine tissue dry weight, corals were fixed in 10 % formalin solution for 48 h, then the skeleton was dissolved by immersion in 5 % HCl that was replaced daily until the skeleton was dissolved (2–4 days). Tissues were rinsed in distilled water and dried for 48 h at 60 °C prior to weighing (±1 mg) and normalizing to area (mg cm-2).

pH was measured using an open-cell autotitrator (Model T50, Mettler-Toledo) calibrated every other day with Tris buffer provided by Dr. Andrew Dickson (Scripps Institution of Oceanography). Total alkalinity (AT) and salinity were measured daily during the first half of the incubation, and then every other day during the second half of the experiment based on the rationale that conditions were demonstrably stable. Seawater analyses were performed on the day of sampling using open-cell potentiometric titration with an automatic titrator (T50, Mettler-Toledo). Measurements were taken on 50-mL samples at *23 °C, and AT calculated after Dickson et al. (2007). Prior to each set of AT measurements, titrations of certified reference material (batch 108) provided by Dr. A. Dickson were performed and yielded values that were ±3 lmol kg-1 of certified values. Parameters of the carbonate system were calculated from salinity, temperature, AT, and pHT using the R package seacarb (Lavigne and Gattuso 2011).

See Comeau et al. (2013) for more details.

comeau2013_calcif.csv