Seawater carbonate chemistry and processes during experiments with coral Acropora eurystoma, 2006

• Main Authors: Schneider, Kenneth, Erez, Jonathan
• Format: Dataset
• Language: English
• Published: PANGAEA 2006
• Subjects: Acropora eurystoma; Alkalinity; total; Alkalinity anomaly technique (Smith and Key; 1975); Animalia; Aragonite saturation state; Benthic animals; Benthos; Bicarbonate ion; Bottles or small containers/Aquaria (<20 L); Calcification/Dissolution; Calcification rate of calcium carbonate; Calcite saturation state; Calculated; see reference(s); Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cnidaria; Coast and continental shelf; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; EXP; Experiment; Experimental treatment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross photosynthesis; Identification; Laboratory experiment; Measured; Net photosynthesis rate; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; pH meter (Radiometer PHM64); Primary production/Photosynthesis; Red Sea; Respiration; Respiration rate; community; Salinity; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.726914; https://doi.org/10.1594/PANGAEA.726914

The rise in atmospheric CO2 has caused significant decrease in sea surface pH and carbonate ion (CO3-2) concentration. This decrease has a negative effect on calcification in hermatypic corals and other calcifying organisms. We report the results of three laboratory experiments designed specifically to separate the effects of the different carbonate chemistry parameters (pH, CO3-2, CO2 [aq], total alkalinity [AT], and total inorganic carbon [CT]) on the calcification, photosynthesis, and respiration of the hermatypic coral Acropora eurystoma. The carbonate system was varied to change pH (7.9-8.5), without changing CT; CT was changed keeping the pH constant, and CT was changed keeping the pCO2 constant. In all of these experiments, calcification (both light and dark) was positively correlated with CO3-2 concentration, suggesting that the corals are not sensitive to pH or CT but to the CO3-2 concentration. A decrease of ~30% in the CO3-2 concentration (which is equivalent to a decrease of about 0.2 pH units in seawater) caused a calcification decrease of about 50%. These results suggest that calcification in today's ocean (pCO2 = 370 ppm) is lower by ~20% compared with preindustrial time (pCO2 = 280 ppm). An additional decrease of ~35% is expected if atmospheric CO2 concentration doubles (pCO2 = 560 ppm). In all of these experiments, photosynthesis and respiration did not show any significant response to changes in the carbonate chemistry of seawater. Based on this observation, we propose a mechanism by which the photosynthesis of symbionts is enhanced by coral calcification at high pH when CO2(aq) is low. Overall it seems that photosynthesis and calcification support each other mainly through internal pH regulation, which provides CO3-2 ions for calcification and CO2(aq) for photosynthesis.