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

Culture pots were placed in large thermally insulated coolers in a temperature-controlled water bath at either 15 or 20°C under saturating illumination of ~150 µmoles photons/m^2/s. pCO2 treatments were supplied to closed culture pots by use of a gas mixing system combining Nitrogen, Oxygen and Carbon Dioxide to specific CO2 partial pressures, 20.9% oxygen and the balance being Nitrogen.

Areal growth: Frond pieces were placed under glass without overlap of branches adjacent to a ruler for scale and imaged using an Infinity 2 camera with attached macro lens mounted on a copy stand. Images and calibrated and surface area of fronds measured using Image J. Measurements were taken at the start and end of the trial. For all measures of growth (by surface area [adj_growth], and biomass [growth_biom] and [growth_dyn]) the calculations are specific growth rates, meaning LOG(measure@t2 / measure@t1)/(t2-t1). For surface area measures (adj_growth) and biomass (as growth_biom), t1 is the initial measure at the start of the experiment and t2 is the final measure at the end of the experiment. For biomass (asgrowth_dyn), t1 is the measure at the start of each weeklong interval and t2 is the measure at the end of the interval. Thus, there were typically 3 such intervals during a trial in which growth was measured and the datum in the column growth_dyn represents the average of those interval specific measures over the course of a trial.

Note: Since tagging individual fronds compromised frond performance, all fronds in a culture pot were treated as sub-samples that were summed to give the datum for the culture pot that was treated as the replicate.

Biomass: Frond pieces were gently blotted dry with paper toweling to remove surface water and weighed at weekly intervals to estimate biomass specific growth rates (growth_biom and growth_dyn). Note: since tagging individual fronds compromised frond performance, all fronds in a culture pot were treated as sub-samples that were summed to give the datum for the culture pot that was treated as the replicate.

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).