A scientific framework for evaluating coral reef resilience to climate change

Abstract

The 21𝑠𝑡 century warming and acidification of tropical oceans will impact the structure and function of coral reef ecosystems. Consequently, conservation efforts are increasingly focused on identifying and protecting reef communities that demonstrate resilience to these changes. In this thesis, I develop a scientific framework for identifying climate change resilience in coral communities and, using Palau’s coral reefs as a case study, demonstrate the application of this approach. First, I use coral skeletal records to evaluate the sensitivity of coral communities to episodes of severe thermal stress. This information reveals coral reef communities that consistently exhibit weak responses to multiple high temperature events. Second, I evaluate coral reef community structure across a strong, natural pH gradient using metrics informed by laboratory ocean acidification studies. The coral communities of Palau’s Rock Island reefs show a level of pH tolerance that is unique amongst reefs studied to date. Third, I conduct laboratory and field experiments to constrain the pH thresholds of these resilient corals and investigate potential mechanisms for pH tolerance. Finally, I combine archipelago-wide coral temperature and pH sensitivity data to construct climate change resilience indices. My study succeeds in identifying a small number of coral communities that have the potential to withstand 21𝑠𝑡 century climate change and highlights the spatial variability in community responses to ocean warming and acidification. Critically, I present a set of scientific tools and approaches for identifying resilient coral reef communities that has applicability to coral reefs worldwide.