Post-disturbance recovery dynamics of connected coral subpopulations

Coral reefs are patchy and connected ecosystems that experience heterogenous environmental conditions, disturbances, and coral population recovery patterns. Connectivity and population growth rates between reef patches can vary at local to subregional (1–100 km) scales, but current coral population models do not bridge the spatial gap between metapopulation-scale (i.e., 100–1000 km) and local population (patch-scale) dynamics (1–10 km). Here, we formulate a density-dependent logistic multi-population dynamics model for reef-building corals that includes the capacity for coral recruitment supported by larvae from autochthonous, local, and allochthonous sources. Model behavior is examined across an idealized parameter range, including limiting cases. It is then applied, with parameters derived from long-term field data sets, to hindcast and interpret the mechanisms driving the coral population recovery observed following a major disturbance. The data represent subpopulations on the fore reef and back reef habitats in Moorea, French Polynesia, that experienced a rapid increase in coral cover following large disturbances from crown-of-thorns sea star outbreak and cyclone in 2010. Analyses of the population model behavior suggest that the observed coral recovery from 2010 to 2019 on the fore reef of Moorea can be explained by an initial immigration of coral larvae from a metapopulation coupled with strong intrinsic growth. This result highlights the importance of population connectivity at scales larger than the spatial scale of disturbances, as well as local conditions conducive to post-settlement success and recovery.