Bicarbonate uptake via an anion exchange protein is the main mechanism of inorganic carbon acquisition by the giant kelp Macrocystis pyrifera (Laminariales, Phaeophyceae) under variable pH, supplement to: Fernández, Pamela A; Hurd, Catriona L; Roleda, Michael Y (2014): Bicarbonate uptake via an anion exchange protein is the main mechanism of inorganic carbon acquisition by the giant kelp Macrocystis pyrifera (Laminariales, Phaeophyceae) under variable pH. Journal of Phycology, 50(6), 998-1008

• Main Authors: Fernández, Pamela A, Hurd, Catriona L, Roleda, Michael Y
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2014
• Subjects: Benthos; Bottles or small containers/Aquaria <20 L; Chromista; Coast and continental shelf; Laboratory experiment; Macroalgae; Macrocystis pyrifera; Ochrophyta; Other metabolic rates; Primary production/Photosynthesis; Single species; South Pacific; Temperate; Species; pH; Net photosynthesis rate, oxygen; Net photosynthesis rate, oxygen, standard error; Inhibition of net photosynthesis; Inhibition of net photosynthesis, standard error; Carbonic anhydrase activity; Carbonic anhydrase activity, standard error; Alkalinity, total; Carbon, inorganic, dissolved; Temperature, water; Salinity; Bicarbonate ion; Carbon dioxide; Carbonate ion; Fugacity of carbon dioxide water at sea surface temperature wet air; Partial pressure of carbon dioxide water at sea surface temperature wet air; Carbonate system computation flag; Aragonite saturation state; Calcite saturation state; Experiment; Spectrophotometric; Potentiometric titration; Coulometric titration; Calculated using SWCO2 Hunter, 2007; Calculated using seacarb after Nisumaa et al. 2010; Ocean Acidification International Coordination Centre OA-ICC; Hurd; Pacific; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.839919; https://doi.pangaea.de/10.1594/PANGAEA.839919

Macrocystis pyrifera is a widely distributed, highly productive, seaweed. It is known to use bicarbonate (HCO3-) from seawater in photosynthesis and the main mechanism of utilization is attributed to the external catalyzed dehydration of HCO3- by the surface-bound enzyme carbonic anhydrase (CAext). Here, we examined other putative HCO3- uptake mechanisms in M. pyrifera under pHT 9.00 (HCO3-: CO2 = 940:1) and pHT 7.65 (HCO3-: CO2 = 51:1). Rates of photosynthesis, and internal CA (CAint) and CAext activity were measured following the application of AZ which inhibits CAext, and DIDS which inhibits a different HCO3- uptake system, via an anion exchange (AE) protein. We found that the main mechanism of HCO3- uptake by M. pyrifera is via an AE protein, regardless of the HCO3-: CO2 ratio, with CAext making little contribution. Inhibiting the AE protein led to a 55%-65% decrease in photosynthetic rates. Inhibiting both the AE protein and CAext at pHT 9.00 led to 80%-100% inhibition of photosynthesis, whereas at pHT 7.65, passive CO2 diffusion supported 33% of photosynthesis. CAint was active at pHT 7.65 and 9.00, and activity was always higher than CAext, because of its role in dehydrating HCO3- to supply CO2 to RuBisCO. Interestingly, the main mechanism of HCO3- uptake in M. pyrifera was different than that in other Laminariales studied (CAext-catalyzed reaction) and we suggest that species-specific knowledge of carbon uptake mechanisms is required in order to elucidate how seaweeds might respond to future changes in HCO3-:CO2 due to ocean acidification. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne et al, 2014) 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). The date of carbonate chemistry calculation is 2014-12-02.