Standard Presentation (15 mins) Australian Marine Sciences Association 2022

Dangerous Demographics in Post‑Bleach Corals Reveal Boom‑Bust Versus Protracted Declines (#92)

Juliano Morais 1 2 3 , Sterling B Tebbett 1 2 3 , David R Bellwood 1 2 3
  1. Research Hub for Coral Reef Ecosystem Functions, James Cook University, Townsville, Queensland, Australia
  2. ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia
  3. College of Science and Engineering, James Cook University, Townsville, Queensland, Australia

Coral bleaching caused by thermal‑stress has changed the biodiversity, and functioning of coral reefs. But how this disturbance affects the fate and dynamics of individual coral colonies, and the spatial extent of coral recruitment, remains relatively unclear, especially during the critical post bleaching ‘recovery’ period. By tracking 1069 individual Acroporaand massive Porites coral colonies for up to 5 years, spanning three bleaching events at Lizard Island, we explored differences in their demographic response to bleaching (mortality, growth, and recruitment). Although Acropora colonies were locally extirpated, substantial local recruitment and fast growth revealed a marked capacity for apparent recovery. However, recruitment was spatially patchy with markedly different trajectories of coral cover regeneration existing among reefs around Lizard Island. By contrast, almost all massive Porites colonies survived and the majority grew in area; yet no new colonies were detected over the 5 years to replace the colonies that were lost. As such, the number of massive Porites may be on a protracted decline. Overall, based on these results I will highlight how these contrasting dynamics of boom-and-bust vs. protracted declines in two major coral groups could have a variety of implications for how reefs will function in a warming world.