An international team of scientists has uncovered new details about coral ecosystems, showing that each coral species hosts its own unique community of microbes. These findings reveal a previously unseen layer of diversity within coral reefs.
The research, which included scientists from the University of Galway, found that coral reefs are home to a wide range of microbes that produce chemicals with strong potential for use in medicine and biotechnology. The study was published in Nature.
Coral Reefs and Their Invisible Diversity
Often described as the rainforests of the sea, coral reefs support about one third of all visible marine life. They are vital biodiversity hotspots and provide important services such as supporting tourism and helping cycle nutrients in ocean ecosystems.
However, scientists now say much of their true diversity exists at a microscopic level. This hidden world, known as the microbiome, cannot be seen with the naked eye but plays a central role in reef health and function.
Large-Scale Study of Coral Microbiomes
With support from the Tara Pacific consortium, researchers examined microbiome samples from 99 coral reefs across 32 Pacific islands. From this work, they reconstructed the genomes of 645 microbial species. More than 99% of these had never been genetically described before.
These microbes are highly specialized partners that live closely with coral hosts. Many act as producers of bioactive compounds, which are chemicals that can influence biological processes and may have medical or industrial value.
The study also found that these coral-associated bacteria contain a wider range of biosynthetic gene clusters, which are the genetic instructions for making natural compounds, than has been recorded anywhere else in the ocean.
Major Gaps in Scientific Knowledge
Dr. Maggie Reddy of the Ryan Institute at the University of Galway emphasized how much remains unknown. She said: “When we compared our findings with microbes found on other reef species, it became clear how little we still know. Of more than 4,000 microbial species identified, only 10% have any genetic information available, and fewer than 1% of the species found only in the Tara Pacific samples have been studied at all. This shows a major gap in our understanding and underlines the need for much more biodiversity surveys, especially in under-studied regions.”
Coral Reefs as a “Molecular Library”
The researchers highlighted an often overlooked aspect of conservation. When coral reefs are damaged or lost, the impact goes beyond visible marine life such as fish, sponges, and seaweeds. It also means losing a vast “molecular library” tied to the microbes that live within them.
Further analysis of newly identified enzymes and compounds suggests there is enormous untapped potential for advances in biotechnology and medicine.
New Enzymes and Biotech Potential
Professor Olivier Thomas of the Ryan Institute said: “The biosynthetic potential of reef-building coral microbiomes rivalled or surpassed that of traditional natural product sources like sponges. Among the biosynthetically rich bacteria in the reef microbiome, we identified previously unknown microorganisms (e.g. Acidobacteriota) living with corals that produce new enzymes with exciting potential biotechnology uses.
“The research is a clear call to action to protect our coral reefs — not just because of their value as a unique ecosystem — but to preserve the unique chemical diversity poised to enable future scientific breakthroughs.”
Global Collaboration and Future Expeditions
The study brought together researchers from the Marine Biodiversity Lab at the Ryan Institute, led by Dr. Maggie Reddy and Professor Olivier Thomas, along with collaborators from ETH Zurich. The work is part of the Tara Pacific consortium, which focuses on understanding how oceans are changing due to climate pressures.
Looking ahead, Dr. Reddy and Professor Thomas will take part in the upcoming Tara Coral expedition in Papua New Guinea this June. Supported by the Tara Foundation and other partners, the expedition will gather new samples and explore why some reef-building corals are more resilient to climate change.
Understanding the Coral Microbiome
The coral microbiome includes bacteria, archaea, fungi, viruses, and algae that live on and inside coral tissue. Together, these organisms form a tightly connected system known as the holobiont, which is essential for coral survival and function.
The samples used in this study were collected during the Tara Pacific expedition between 2016 and 2018. This effort has provided one of the most detailed maps yet of coral microbiomes across a region that contains about 40% of the world’s coral reefs.
