Plocamium cartilagineum was collected from Catalina Island in June - Nov. 2014 and Jan. 2015.

Seawater samples were collected over a 30-hour time course of pH drift experiments with Plocamium cartilagineum to test mechanism of carbon acquisition by alga and the effect on carbonate chemistry parameters reported in these datasets. Samples were collected at 0, 2, 6, 20, 24 and 30 hours and parameters of carbonate chemistry were measured (DIC,CO2, HCO3,CO3-described below). pH drift assay experiments consisted of 2 independent variables; inhibitor treatment and algal presence, with 3 and 2 levels, respectively for each independent variable (see parameters section). Two replicate water samples were collected from each of 9 experimental culture pots of algae grown for 3 weeks at different combinations of pCO2 and temperature during each of 7 experimental trials.

Carbonate chemistry parameters were measured by sampling pH and total alkalinity (TA) of water samples. pH was determined using the m-cresol indicator dye method in a spectrophotometer (Dickson et al. 2007). TA samples were analyzed by potentiometric titration coupled to a pH electrode calibrated using certified reference material (CRM) from the Dickson laboratory at Scripps Oceanographic Institute and the pH electrode calibrated using TRIS buffer (Dickson et al. 2007). TA and carbonate parameters were calculated from potentiometric titration data and spectrophotometric pH data.

Methodology Reference:
Dickson AG, Sabine CL, Christian JR (2007). Guide to Best Practices for Ocean CO2 Measurements.

Note: Trial 1 was a pilot test of culture system and methodological procedures so was not used for data collection in the testing of hypotheses.

See Supplemental Files for a table of culture conditions for each of the 8 trials (pdf).