Coral-algae metabolism and diurnal changes in the CO2-carbonate system of bulk sea water

• Main Authors: Jokiel, Paul L, Jury, Christopher P, Rodgers, Ku'ulei
• Format: Dataset
• Language: English
• Published: PANGAEA 2014
• Subjects: Alkalinity; total; Animalia; Aragonite saturation state; Benthic animals; Benthos; Bicarbonate ion; Calcification/Dissolution; Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cnidaria; Coast and continental shelf; Experiment; Flow rate; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gracillaria salicornia; Irradiance; Laboratory experiment; Macroalgae; Mesocosm or benthocosm; Montipora capitata; Net calcification rate of calcium carbonate; Net photosynthesis rate; North Pacific; OA-ICC; Ocean Acidification International Coordination Centre; Other; Oxygen; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Plantae; Potentiometric; Potentiometric titration; Primary production/Photosynthesis; Rhodophyta; Salinity; Single species; Species; Species interaction; Temperature; water; Time of day; Tropical; Pacific; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.839068; https://doi.org/10.1594/PANGAEA.839068

Precise measurements were conducted in continuous flow seawater mesocosms located in full sunlight that compared metabolic response of coral, coral-macroalgae and macroalgae systems over a diurnal cycle. Irradiance controlled net photosynthesis (Pnet), which in turn drove net calcification (Gnet), and altered pH. Pnet exerted the dominant control on [CO3]2- and aragonite saturation state (Omega arag) over the diel cycle. Dark calcification rate decreased after sunset, reaching zero near midnight followed by an increasing rate that peaked at 03:00 h. Changes in Omega arag and pH lagged behind Gnet throughout the daily cycle by two or more hours. The flux rate Pnet was the primary driver of calcification. Daytime coral metabolism rapidly removes dissolved inorganic carbon (DIC) from the bulk seawater and photosynthesis provides the energy that drives Gnet while increasing the bulk water pH. These relationships result in a correlation between Gnet and Omega arag, with Omega arag as the dependent variable. High rates of H+ efflux continued for several hours following mid-day peak Gnet suggesting that corals have difficulty in shedding waste protons as described by the Proton Flux Hypothesis. DIC flux (uptake) followed Pnet and Gnet and dropped off rapidly following peak Pnet and peak Gnet indicating that corals can cope more effectively with the problem of limited DIC supply compared to the problem of eliminating H+. Over a 24 h period the plot of total alkalinity (AT) versus DIC as well as the plot of Gnet versus Omega arag revealed a circular hysteresis pattern over the diel cycle in the coral and coral-algae mesocosms, but not the macroalgae mesocosm. Presence of macroalgae did not change Gnet of the corals, but altered the relationship between Omega arag and Gnet. Predictive models of how future global changes will effect coral growth that are based on oceanic Omega arag must include the influence of future localized Pnet on Gnet and changes in rate of reef carbonate dissolution. The correlation between Omega ...