Coral Reefs: Sinks of Atmospheric CO2 ?

Quantification of air-sea CO₂ exchange over coral reefs has relied primarily on measurements of the CO₂ partial pressure (pCO₂) gradient between the water overlying a reef and the lower atmosphere. A gas transfer velocity based on wind speed is then used to estimate the air-sea CO₂ mass exchange. While this approach may be suitable over the oceans or where instrumented buoys have been deployed for long-term monitoring, the method overlooks many factors that influence turbulent transport and air-sea CO₂ exchange. These include surfactants, bubble exchange, atmospheric turbulence, and wave breaking, which may be particularly important over near shore fringing coral reefs.

 

Using eddy covariance (EC) systems deployed at the shoreline adjacent to coral reefs and on pontoons we show through direct measurements these ecosystems may be net sinks of atmospheric CO₂. Results show sequestration of atmospheric CO₂ by healthy coral reefs and adjacent lagoons at time scales of several days to several months exceed published CO₂ sequestration rates of mature pine plantations measured by EC by an order of magnitude. These findings highlight the importance of coral reefs in carbon budgets in addition to their widely known ecosystem services and societal benefits. Conserving coral reef ecosystems and ensuring they remain healthy and resilient to the threats of climate change, pollution, overfishing, tourism, and mining should be a priority. Future research will aim to track the CO₂ influx through coral reef ecosystems.