Hurricanes enhance coral connectivity but also superspread coral diseases: Connectivity matrices

Climate change poses an existential threat to coral reefs. A warmer and more acidic ocean weakens coral ecosystems and increases the intensity of hurricanes. The wind-wave-current interactions during a hurricane deeply change the ocean circulation patterns and hence affect the dispersal of coral larvae and coral disease agents. Here we assessed the impact of major hurricane Irma (Sept. 2017) on coral larval and stony coral tissue loss disease connectivity in Florida’s Coral Reef. We coupled high-resolution coastal ocean circulation and wave models to simulate the dispersal of virtual coral larvae and disease agents between thousands of reefs. While being a brief event, our results suggest the passage of hurricane Irma strongly increased the probability of long-distance exchanges while reducing larval supply. It created new connections that could promote coral resilience but also probably accelerated the spread of the coral disease by about a month. As they become more intense, hurricanes’ double-edged effect will become increasingly pronounced, contributing to increased variability and an accelerated rate of change within coral reef ecosystems.

Methods
Connectivity matrices were computed by simulating the dispersion of virtual particles using the high-resolution unstructured-mesh coupled wave-ocean model SLIM (https://www.slim-ocean.be)