Linking coral recruitment to reef recovery in the Anthropocene
- Speare, Kelly Elizabeth
- Advisor(s): Burkepile, Deron E.
Coral reefs are among the most biodiverse and valuable ecosystems on Earth, providing food, coastal protection, and jobs for over a billion people worldwide. Coral reefs are also among the most imperiled by global climate change and local stressors that cause degradation. Disturbances that kill corals are becoming more frequent and intense and it has become increasingly important to understand how disturbances impact the recovery potential of coral reefs and which processes are most important for driving recovery. In my dissertation work I utilized time series data from the Moorea Coral Reef LTER along with observational approaches and field experiments to investigate the impacts of disturbances on coral communities, identify processes that drive recovery after disturbance, and understand the mechanisms shape early demographic processes in corals. I first investigated the impacts of a severe marine heatwave on coral communities in Moorea, French Polynesia, and found that coral bleaching caused disproportionate mortality of the largest, most fecund corals and near complete loss of newly-settled coral recruits. This work suggests that climate change may cryptically erode the recovery capacity of coral reefs by disproportionately impacting the coral life stages most important for recovery. Reefs in Moorea have a history of recovering from disturbance, and prior to the bleaching event reefs were recovering from an outbreak of the coral-eating sea star, Acanthaster planci, and a cyclone that killed nearly all corals on the outer reefs. I investigated the drivers of differences in recovery rates between deep and shallow reefs and found that slower recovery on deeper reefs was driven by lower rates of coral recruitment and post-settlement bottlenecks that limited the establishment of new corals. My work points to the importance of post-settlement processes that dictate rates of coral recruitment and ultimately reef recovery. Next, I investigated how benthic communities shape the settlement choices of coral larvae, and found that larvae made complex settlement choices that were strongly influenced by benthic community composition at the scale of millimeters. This work improves our ability to understand and predict how coral communities will respond to disturbances in the Anthropocene.