| Summary: | Coral reefs throughout the world are under increasing pressure from anthropogenic perturbations which threaten to shift reefs from a state of net CaCO3 production to net dissolution. Once a reef becomes net dissolving it can no longer maintain the growth of CaCO3 structures critical for sustaining the diversity and abundance of life on coral reefs. Therefore it is critical to monitor and predict how anthropogenic forcings will affect the balance of net ecosystem calcification in reef ecosystems. Currently, most coral reef monitoring projects rely on visual measurements of benthic composition and do not measure seawater chemistry parameters such as total alkalinity (TA) and dissolved inorganic carbon (DIC). Vector analysis of TA and DIC can be used to determine the relative influence of organic (photosynthesis/respiration) versus inorganic (CaCO3 production/ dissolution) processes occurring on a coral reef. Results from a mesocosm study demonstrate that benthic community composition is reflected in the TA-DIC slope of the overlying seawater. An analysis of 23 coral reef locations around the globe showed that there is a diverse range in TA-DIC slopes (0.24 to 1.36), indicating a large range in the biogeochemical function of reef ecosystems. A simple model demonstrated that reefs with slopes greatly different from 0.95 have a dramatic increase in the diel variability of seawater pH, which is exacerbated by ocean acidification. Monitoring the pulse of coral reefs via TA and DIC measurements through time and space could help to better inform conservation and management efforts.
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