Dynamics and Drivers of Coral Reef Resilience

Abstract

Coral reefs are epicenters of biodiversity and support millions of people worldwide. In light of local and global stressors, including overfishing and increasing sea surface temperatures, there is a critical need to identify the determinants of coral population persistence and recovery potential. This thesis examines the interaction among the fundamental ecological processes of larval dispersal, competition, and mortality in mediating the resilience of coral populations. In Chapter 2, I present a spatially implicit analytical model of coral-algal competition that incorporates coral larval dispersal. Here, I show that recruitment plays a vital role in the maintenance and recovery of coral populations, even when coral reproduction is seasonal in nature. Additionally, the particular characteristics of recruitment, namely the input rate and duration, can affect the ability of reefs to recover from an algal- to a coral-dominated regime in the presence of disturbance. In Chapter 3, I apply this model to a spatially realistic network of reefs in the Coral Triangle (CT) region of the Indo-Pacific. Using larval connectivity data derived from an ocean circulation model, I characterize coral resilience across the CT by simulating projected temperature increase scenarios. In addition, I show that these patterns are driven by mortality due to thermal stress as well as recruitment patterns. Finally, in Chapter 4, I allow for heterogeneity in coral thermal tolerance both across the CT and within individual reef patches. I illustrate that larval dispersal, via the transport of heritable traits throughout the system, can facilitate a relatively rapid adaptive response to thermal stress under selective pressure.