Experiment: Elevated CO2 levels affect the activity of nitrate reductase and carbonic anhydrase in the calcifying rhodophyte Corallina officinalis

• Main Authors: Hofmann, Laurie C, Straub, Susanne M, Bischof, Kai
• Format: Dataset
• Language: English
• Published: PANGAEA 2013
• Subjects: Alkalinity; total; Ammonium uptake rate; Aragonite saturation state; Benthos; Bicarbonate ion; BIOACID; Biological Impacts of Ocean Acidification; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbonic anhydrase; activity; Coast and continental shelf; Containers and aquaria (20-1000 L or < 1 m**2); Corallina officinalis; Date; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Group; Identification; Laboratory experiment; Macroalgae; Nitrate reductase activity; Nitrate uptake rate; North Atlantic; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide; standard deviation; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Phosphate uptake rate; Plantae; Rhodophyta; Salinity; Single species; Species; Temperate; Temperature; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.830299; https://doi.org/10.1594/PANGAEA.830299

The concentration of CO2 in global surface ocean waters is increasing due to rising atmospheric CO2 emissions, resulting in lower pH and a lower saturation state of carbonate ions. Such changes in seawater chemistry are expected to impact calcification in calcifying marine organisms. However, other physiological processes related to calcification might also be affected, including enzyme activity. In a mesocosm experiment, macroalgal communities were exposed to three CO2 concentrations (380, 665, and 1486 µatm) to determine how the activity of two enzymes related to inorganic carbon uptake and nutrient assimilation in Corallina officinalis, an abundant calcifying rhodophyte, will be affected by elevated CO2 concentrations. The activity of external carbonic anhydrase, an important enzyme functioning in macroalgal carbon-concentrating mechanisms, was inversely related to CO2 concentration after long-term exposure (12 weeks). Nitrate reductase, the enzyme responsible for reduction of nitrate to nitrite, was stimulated by CO2 and was highest in algae grown at 665 µatm CO2. Nitrate and phosphate uptake rates were inversely related to CO2, while ammonium uptake was unaffected, and the percentage of inorganic carbon in the algal skeleton decreased with increasing CO2. The results indicate that the processes of inorganic carbon and nutrient uptake and assimilation are affected by elevated CO2 due to changes in enzyme activity, which change the energy balance and physiological status of C. officinalis, therefore affecting its competitive interactions with other macroalgae. The ecological implications of the physiological changes in C. officinalis in response to elevated CO2 are discussed.