DOI: 10.5061/dryad.0cfxpnw98
title: Hurricanes enhance coral connectivity but also superspread coral diseases: Connectivity matrices

description: 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.
description: 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)
description: # Hurricanes enhance coral connectivity but also superspread coral
 diseases: connectivity matrices
 [https://doi.org/10.5061/dryad.0cfxpnw98](https://doi.org/10.5061/dryad.0cfxpnw98) Connectivity matrices obtained from the simulated dispersal of coral larvae and stony coral tissue loss disease (SCTLD) agents in Florida's Coral Reef before and after the landfall of Hurricane Irma (2017). ## Description of the data and file structure `hydro_outputs_irma_gcb_2024.zip` contains the simulated currents used to compute the connectivity matrices: * These currents can be visualized by opening `slim.xdmf` with [Paraview](https://www.paraview.org/). * The output models are stored as binary files (`.abin` extension). The metadata associated to each binary file (size, data type) are stored in the corresponding `.ameta` files.(formatted text format). * The coordinates of the mesh nodes are stored in `slim/mesh/geometry.*` and the mesh topology in `slim/mesh/topology.*`. * The simulated sea surface elevation and depth-averaged currents are respectively stored in `slim/data/eta.*` and `slim/data/uv.*`. `connectivity_matrices_irma.zip` contains the connectivity matrices used to estimate and compare the connectivity indicators at each reef: * reef_map: the shape file of the reefs used for the simulation. * larvae: the connectivity matrices obtained from the dispersal of coral larvae before and after the landfall of Irma. The rows and columns of the matrices correspond to the polygons of the reef map. The `cm_*.npz` files the number of larvae exchanged between all pairs of reefs. The `n_seeded_*.npy` give the number of larvae released on each reef polygon * sctld: same as "larvae" for SCTLD agents, but matrices rows are already normalized by the number of released agents on each reef polygon ## Sharing/Access information The data is also (currently) available [here](https://uclouvain-my.sharepoint.com/:f:/g/personal/thomas_dobbelaere_uclouvain_be/EuRwpuKKnytJvnkfshpBeA8BhwYU19c5sLEe8n3fnPmkjQ?e=pIUMxM) ## Code/Software The matrices were obtained using the high-resolution unstructured-mesh model [SLIM](https://www.slim-ocean.be), whose interface is implemented in Python. * .npz files can be read using the `scipy.sparse` * .npy files can be read using `numpy` * .abin files can be read as memory maps using `numpy.memmap` using the information of the .ameta files