Dataset: Carbonate chemistry data collected as part of a study of the "Community context and pCO2 impact the transcriptome of the "helper" bacterium Alteromonas in co-culture with picocyanobacteria"

   Synechococcus cultures were grown under similar conditions to those described in our previous experiment with Prochlorococcus (Hennon et al., 2017). Briefly, all cultures were prepared in acid-washed conical-bottom glass centrifuge tubes containing 13 mL of artificial seawater (ASW) amended with nutrient stocks (Hennon et al., 2017) and with acid and/or base to control pCO2. ASW (per L: 28.41 g NaCl, 0.79 g KCl, 1.58 g CaCl2*2H2O, 7.21 g MgSO4*7H2O, 5.18 g MgCl2*6H2O) was sterilized in acid-washed glass bottles, amended with 2.325 mM (final concentration) of filter-sterilized sodium bicarbonate, then bubbled with sterile air overnight. Synechococcus cultures were grown in SEv (per L: 32 μM NaNO3, 2 μM NaH2PO4, 20 μL SN trace metal stock, and 20 μL F/2 vitamin stock). The primary differences between this medium and the PEv medium used in our earlier Prochlorococcus study are the nitrogen source (NO3- vs. NH4+, with molar concentration of N and N:P ratios identical to PEv) and the addition of F/2 vitamins (Hennon et al., 2017). Carbonate chemistry of each media batch was determined prior to pCO2 manipulations by measuring alkalinity and pH by titration and colorimetry, respectively (Dickson et al., 2007) and then using the oa function in seacarb package in R to determine how much hydrochloric acid and bicarbonate (for 800 ppm pCO2) or sodium hydroxide (for 400 ppm pCO2) was needed to achieve desired experimental conditions (Gattuso and Lavigne, 2009).  Acid and base amendments were introduced immediately prior to inoculation. Cultures were grown in a Percival growth chamber at 21º C under 150 μmol photons m-2 s-1 on a 14:10 light:dark cycle. Synechococcus cultures were grown on a rotating tissue culture wheel at approximately 60 rpm. After addition of amendments, absorbance values at 434, 578, and 730 nm were collected both before and after injection of m-cresol purple dye, and again after a second dye injection to correct for the impact of dye addition on solution pH.  Equations from (Dickson et al., 2007) were used to compute the pH.  The data are provided in the form of an Excel spreadsheet containing the necessary formulas for computing the pH from the absorbance data.  pH assays were performed in microtiter plates using a BioTek H1 plate reader with an automated dye injection mechanism and temperature control.