4:25 PM - 4:40 PM
[ACG43-09] Variation in coral calcifying fluid pH across coral habitable latitude
Keywords:coral, biomineralisation, pH, aragonite saturation state
Since the accretion of coral skeletons occurs within the calcifying fluid (CF) between coral soft tissues and hard skeletons, the chemical composition of the CF, such as pH and aragonite saturation state (Ωara), is likely to influence coral calcification. In this study, the variation in pH and Ωara in CF of the reef-building corals collected from a wide latitudinal range (from ~7°N to 34°N) are derived using the geochemical tools to understand the contribution of environment to the chemical composition in the CF.
The pH and Ωara in the CF were derived from boron isotopes and boron concentration in the coral skeletons. Specimens were collected from the tropical (~7°N) to the temperate ocean (~34°N) and hence experienced different temperatures (annual average between ~22 - 29℃). The pH in the CF showed an increasing trend from lower to higher latitude with decreasing temperature. We found that Ωara in the CF ranges between 10-20 without a significant relation with latitude. This fact suggests corals can maintain Ωara in CF within similar range regardless of the difference in seawater environments among their habitats. Although Ωara is similar among corals, calcification rate is generally higher in tropical zone, implying that temperature mainly controls the coral calcification rate.