Award: OCE-2316580

In the summer of 2022, an unknown coral disease was observed causing mortality on the remote reefs of the Flower Garden Banks National Marine Sanctuary in the northwestern Gulf of Mexico. These remarkable reefs have historically experienced low disease incidence, and there was immediate concern that the disease could be stony coral tissue loss disease (SCTLD). This project brought together a multidisciplinary team of marine ecologists, coral epidemiologists, molecular ecologists, and modelers who have spent years integrating methodologies to study coral disease, including work in the U.S. Virgin Islands (NSF #2109622).

The aim of this project was to leverage the team’s collective expertise to investigate the nature and origin of the outbreak. Using coupled biophysical models, we demonstrated that disease agents could reach these remote reefs as passive particles dispersed from upstream sources. These deleterious connectivity events appear most likely during periods of Loop Current extension—indeed, a period of anomalously high connectivity from Mexican and Mesoamerican reefs immediately preceded the 2022 outbreak.

While the mechanism of within-reef disease transmission remains unclear, the team generated 3-dimensional Large Area Images (orthomosaics) of Flower Garden Banks reefs over three consecutive years (2022–2024) to track disease lesions within and among coral colonies. These sequential mosaics will allow us to characterize density- and frequency-dependent transmission processes within coral communities.

These high-resolution orthomosaics were produced by highly trained scientific divers. Tens of thousands of images were processed using structure-from-motion algorithms to create 3D point clouds and 2D orthorectified mosaics with sub-centimeter resolution. The resulting 625 m² mosaics were aligned across years and segmented to track individual colonies and disease lesions through both time and space.

To explore potential sources of disease, we simulated disease dispersal under 20 years of hydrodynamic forcing. We identified upstream connectivity from reefs in Mexico, Mesoamerica, and Cuba and correlated these connections with changes in major current regimes. In years when coral disease was observed in the northern Gulf of Mexico, the Loop Current was typically extended, facilitating rapid long-distance biophysical connections.

To support ongoing efforts to determine the etiology of the disease, coral tissue samples were analyzed via histopathology and compared with samples from the U.S. Caribbean and Florida. While much remains unknown, preliminary findings suggest that this outbreak does not share the same etiology or pathology as recent SCTLD events elsewhere.

This project supported field, simulation, and laboratory work for three graduate students and five undergraduates. It has resulted in several oral presentations at the 2024 Ocean Sciences Meeting, the 2024 Reef Futures Meeting, and the 2025 Benthic Ecology Meeting.

Last Modified: 06/24/2025
Modified by: Daniel M Holstein