Award: OCE-0417412

The Moorea Coral Reef (MCR) LTER explores community and ecosystem effects of pulsed perturbations and slowly changing environmental drivers on coral reefs, ecologically and economically important ecosystems that are at high risk from local and global stressors. Field operations are based from the University of CaliforniaÆs field station on Moorea, French Polynesia, and the site includes coral habitats in lagoons and the offshore fore reef. Staring in 2007, the fore reef was perturbed by an outbreak of the corallivorous Crown-of-Thorns Seastar (COTS) followed by a cyclone in early 2010. These events killed almost all corals on the fore reef but had little effect in the lagoon. Coral reefs always have been impacted by these kinds of massive disturbances, but never before has there been a reef system with such comparable levels of prior research, high resolution in situ instrumentation and time series measurements made before, during and after such a major set of perturbations. This is providing the MCR with an unparalleled scientific opportunity to address fundamental, unresolved questions regarding disturbance and recovery of coral reefs. The MCR collected several years of time series data before the recent perturbations occurred. Community trajectories from coral reefs in other regions reveal that a rapid return to coral dominance is prevented if macroalgae become widely established following the sudden death of coral, a state shift that is becoming more common in the Caribbean and Pacific. Our research focused on the processes that prevent a shift to macroalgal dominance following loss of coral. Herbivory has long been known to be a critical process on coral reefs that can prevent a state shift to macroalgae, and management strategies to enhance resilience of coral reefs emphasize actions to avoid overfishing herbivores. Despite this, it is not well understood how herbivores respond to the sudden, widespread loss of coral. MCRÆs time series data and field experiments provided novel insights into behavioral and dynamical responses of coral reef herbivores that have fundamental implications for management strategies to enhance resilience. Following the recent perturbations to the fore reef, the abundance and biomass of herbivorous fishes increased rapidly, and grazing by these fishes prevented a state shift to macroalgae. Importantly, most of these herbivores were parrotfishes, which initially recruit to nursery habitat within the lagoon before moving to the fore reef later in life. Our work reveals critical connectivity between inshore and offshore reefs, and indicates that protecting nursery habitat of key herbivores is essential for maintaining reef resilience. While coral cover has fluctuated tremendously on the fore reef, it has varied far less in lagoons. However, previous perturbations triggered an important shift in the species composition of corals in lagoon habitats. The abundance of acroporid corals fell, especially the thicket-forming staghorn coral, a major provider of habitat for fishes and invertebrates. Staghorn Acropora has recovered little over the past 30 years. Consequently we asked what governs the population dynamics of key species of corals. We found that acroporid corals are more susceptible than other types of corals to predators. The reason for the slow recovery of staghorn Acropora is that they must be defended from corallivores by a territorial farmerfish. We also found a second, potentially ubiquitous means by which coral-dwelling fishes can greatly affect their coral habitat. Numerous species of fishes use coral structure for shelter; we found that the abundance of fishes is positively related to the size of their coral host, and that the growth rate of the coral is enhanced by its associated fishes due to excretion of nitrogenous waste. Since most of the fish are planktivores, this represents an important flow of nutrients from the water column to the benthos. ...