Standard Presentation Australian Marine Sciences Association Annual Meeting 2023

On the fate of dead coral colonies (#214)

Juliano Morais 1 , Renato Morais 2 , Sterling Tebbett 1 , David Bellwood 1
  1. Research Hub for Coral Reef Ecosystem Functions, James Cook University, Townsville, Queensland, Australia
  2. École Pratique des Hautes Études, Université Paris Sciences et Lettres, Perpignan, France

Climate change has been negatively impacting carbonate budgets dynamics on coral reefs. While bleaching and coral mortality are well documented, the fate of coral colonies after their death, including their erosion rates, are still poorly known. Here, we followed the fate of 143 recently dead individual coral colonies with complex growth forms. These colonies were tracked for up to 5 years, allowing detailed examination of erosion rates and post-mortality structural persistence. We also tested how variables that are commonly used in coral reef erosion studies relate to spatial and temporal variability in the erosion rates of dead coral colonies. We revealed rapid erosion of dead coral colonies, with an average of 79.7% of dead colonies completely disintegrating within 60 months. The predicted half-life of a dead coral colony was 40 months, with limited variation among wave exposure levels. Remarkably, we found no effect of estimated parrotfish bioerosion, wave exposure, nor coral growth form, on observed erosion rates. Overall, based on these results, I will highlight how our understanding of the erosion of dead corals, the role of corals with complex growth forms in reef growth, and the role of parrotfishes in reef erosion may be more limited than previously thought.