Changing carbonate budgets and the maintenance of coral reefs and reef islands

The ecology and structure of many tropical coral reefs have altered markedly over the past few decades. Drivers of this degradation range from direct local damage from destructive human practices to global scale climate stressors, and especially those associated with elevated sea‐surface temperature anomalies. A major consequence of these climatic and pervasive local stressors has often been a rapid decrease in the abundance of habitat building corals, which has consequently reduced reef structural complexity and coral carbonate production rates. Equally, many reefs have been impacted by changes (both increases and decreases) in the abundance of bioeroding taxa such as parrotfish, urchins, sponges and microendolithic organisms. The collective effect has been to alter the rates and relative balance of carbonate producing and eroding processes on many reefs. Such changes are of increasing interest because these processes directly regulate net rates of reef carbonate production and sediment generation, and collectively can impact upon multiple geo‐ecological functions on reefs. These functions include reef‐building and the capacity of reefs to accrete vertically in response to sea‐level rise, and the supply of sands necessary to sustain beaches and reef islands. This talk will discuss recent progress in developing methodologies to estimate rates of reef carbonate production, reef growth and sediment generation. It will then use selected recent field examples to highlight changes in these processes in response to ecological disturbance, and highlight the potential to integrate these data into numerical and lab-based modelling approaches than be used to predict coastal wave exposure under future sea level rise scenarios.