Woods Hole, Mass. (January 20, 2026) — Researchers at the Woods Hole Oceanographic Institution (WHOI), in collaboration with the University of the Virgin Islands, have made a groundbreaking discovery that could revolutionize how coral reef health is monitored globally. By analyzing microorganisms in the seawater surrounding corals, scientists have identified a powerful indicator of coral disease, offering a non-invasive alternative to traditional methods.
Coral reefs, which support more than 25 percent of all marine life and sustain the livelihoods of approximately one billion people worldwide, face significant threats from diseases. Traditionally, diagnosing coral diseases has relied on visual inspections by divers, often after the disease has already taken hold. However, the new study, published in Cell Reports Sustainability, reveals that changes in the seawater microbiome adjacent to corals can more accurately indicate disease presence than the microbes residing within the coral tissue itself.
Revolutionizing Coral Disease Detection
“This study shows that the ocean water surrounding a coral can tell us a lot, including when that coral is sick,” said Jeanne Bloomberg, lead author of the study and a WHOI–MIT Joint Program graduate student. “By identifying a strong disease signal in the surrounding seawater, rather than in the coral tissue, we’re laying the groundwork for a diagnostic tool that is both effective and non-invasive.”
The research team conducted a longitudinal study on brain coral (Colpophyllia natans) colonies over four years near St. John in the U.S. Virgin Islands. This period included the onset of stony coral tissue loss disease (SCTLD), providing valuable baseline data to monitor disease progression. From 2020 to 2024, scientists collected samples from both coral tissue and the surrounding seawater. Genetic sequencing revealed that while the microbes within coral tissue varied—even in healthy corals—the microbes in the surrounding seawater remained stable near healthy corals but changed significantly when corals became diseased during the SCTLD outbreak.
Understanding SCTLD and Its Impact
SCTLD has emerged as one of the most devastating coral diseases recorded, spreading rapidly across the Caribbean over the last decade. Although antibiotic treatments can slow or halt disease progression in individual corals, the pathogen responsible for SCTLD remains unidentified.
“These seawater microbes seem to react to material released by diseased corals,” Bloomberg explained. “This effect was strongest during the height of the outbreak, when disease was most widespread on the reef.”
“Our findings provide compelling evidence that seawater microbiomes can be used to diagnose coral disease and potentially other reef disturbances,” said Amy Apprill, an associate scientist at WHOI and project lead on the WHOI Reef Solutions Initiative.
Implications for Coral Reef Management
The study’s findings could have transformative implications for reef managers, particularly in the Caribbean, where SCTLD has caused severe losses of reef-building corals, leading to significant economic and ecological consequences.
“Developing diagnostic tools for coral disease based on this work could help us respond faster and more strategically to protect what remains,” said Marilyn Brandt, research professor at the University of the Virgin Islands and a co-author of the study.
By demonstrating that reef seawater carries a measurable disease signal, the research opens new pathways for scalable, non-destructive reef monitoring—a critical need as coral reefs face increasing pressures from warming oceans, pollution, and emerging diseases. As coral reefs continue to decline globally, tools that allow scientists to forecast reef health, rather than merely document loss, are essential.
Looking Ahead
This research represents a significant step toward protecting coral reefs before irreversible damage occurs. “This work highlights WHOI’s commitment to advancing innovative, practical solutions for ocean health,” Apprill added. “Understanding the invisible microbial world around corals may be key to safeguarding reefs for future generations.”
The study was funded by the National Science Foundation and conducted with permitting support from the University of the Virgin Islands Department of Planning and Natural Resources. As researchers continue to refine this diagnostic approach, the potential for early intervention and improved coral reef management becomes increasingly promising.
