Seawater carbonate chemistry, gross photosynthesis and metabolically induced rate of pH change during experiments with macroalgae, 2012, supplement to: Cornwall, Christopher Edward; Hepburn, Christopher D; Pritchard, Daniel; Currie, Kim I; McGraw, Christina M; Hunter, Keith A; Hurd, Catriona L (2012): Carbon-use strategies in macroalgae: Differential responses to lowered pH and implications for ocean acidification. Journal of Phycology, 48(1), 137-144

• Main Authors: Cornwall, Christopher Edward, Hepburn, Christopher D, Pritchard, Daniel, Currie, Kim I, McGraw, Christina M, Hunter, Keith A, Hurd, Catriona L
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2012
• Subjects: Benthos; Bottles or small containers/Aquaria <20 L; Chlorophyta; Chromista; Coast and continental shelf; Corallina officinalis; Laboratory experiment; Macroalgae; Ochrophyta; Plantae; Primary production/Photosynthesis; Rhodophyllis gunnii; Rhodophyta; Schizoseris sp.; Single species; South Pacific; Temperate; Ulva sp.; Undaria pinnatifida; Experimental treatment; Salinity; Temperature, water; pH; pH, standard error; Alkalinity, total; Alkalinity, total, standard error; Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbon dioxide, total; Carbon dioxide, standard error; Bicarbonate; Bicarbonate ion, standard error; Carbonate ion; Carbonate ion, standard error; Species; Gross photosynthesis rate, oxygen; Gross photosynthesis rate, oxygen, standard error; Metabolically induced rate of pH change; Metabolically induced rate of pH change, standard error; Carbonate system computation flag; Carbon dioxide; Partial pressure of carbon dioxide water at sea surface temperature wet air; Fugacity of carbon dioxide water at sea surface temperature wet air; Bicarbonate ion; Aragonite saturation state; Calcite saturation state; pH meter Orion; Titration; Calculated using SWCO2 Hunter, 2007; Calculated, see references; Calculated using seacarb after Nisumaa et al. 2010; Calculated; Calculated using CO2SYS; European network of excellence for Ocean Ecosystems Analysis EUR-OCEANS; European Project on Ocean Acidification EPOCA; Ocean Acidification International Coordination Centre OA-ICC; Cornwall; Currie; Hurd; Orion; Pacific; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.775819; https://doi.pangaea.de/10.1594/PANGAEA.775819

Ocean acidification (OA) is a reduction in oceanic pH due to increased absorption of anthropogenically produced CO2. This change alters the seawater concentrations of inorganic carbon species that are utilized by macroalgae for photosynthesis and calcification: CO2 and HCO3 increase; CO32 decreases. Two common methods of experimentally reducing seawater pH differentially alter other aspects of carbonate chemistry: the addition of CO2 gas mimics changes predicted due to OA, while the addition of HCl results in a comparatively lower [HCO3]. We measured the short-term photosynthetic responses of five macroalgal species with various carbon-use strategies in one of three seawater pH treatments: pH 7.5 lowered by bubbling CO2 gas, pH 7.5 lowered by HCl, and ambient pH 7.9. There was no difference in photosynthetic rates between the CO2, HCl, or pH 7.9 treatments for any of the species examined. However, the ability of macroalgae to raise the pH of the surrounding seawater through carbon uptake was greatest in the pH 7.5 treatments. Modeling of pH change due to carbon assimilation indicated that macroalgal species that could utilize HCO3 increased their use of CO2 in the pH 7.5 treatments compared to pH 7.9 treatments. Species only capable of using CO2 did so exclusively in all treatments. Although CO2 is not likely to be limiting for photosynthesis for the macroalgal species examined, the diffusive uptake of CO2 is less energetically expensive than active HCO3 uptake, and so HCO3-using macroalgae may benefit in future seawater with elevated CO2. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne and Gattuso, 2011) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI).