Publication Date:
2024-03-15
Description:
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.
Keywords:
Alkalinity, total; Aragonite saturation state; Aromoana; Benthos; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Calculated using SWCO2 (Hunter, 2007); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbonic anhydrase activity; Carbonic anhydrase activity, standard error; Chromista; Coast and continental shelf; Coulometric titration; EXP; Experiment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Inhibition of net photosynthesis; Inhibition of net photosynthesis, standard error; Laboratory experiment; Macroalgae; Macrocystis pyrifera; Net photosynthesis rate, oxygen; Net photosynthesis rate, oxygen, standard error; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Potentiometric titration; Primary production/Photosynthesis; Salinity; Single species; South Pacific; Species; Spectrophotometric; Temperate; Temperature, water
Type:
Dataset
Format:
text/tab-separated-values, 465 data points
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