A team of researchers from Monaco and beyond has discovered how extreme heatwaves are disrupting the microscopic life that helps Mediterranean red corals survive.

The Mediterranean’s iconic red coral, Corallium rubrum, is facing a new challenge: marine heatwaves. A team of scientists, including Denis Allemand, Christine Ferrier-Pagès, and Romie Tignat-Perrier from the Centre Scientifique de Monaco (CSM), has uncovered how these extreme temperature events are changing the coral’s tiny microbial partners, potentially making it harder for them to cope with climate change.

The research, carried out in collaboration with Chanel and supported by the Monaco Government, focused on the coral’s eukaryome—the community of microscopic organisms living inside it. By studying 56 coral colonies from different parts of the Mediterranean, the scientists found that healthy corals host a stable mix of microbes, including certain dinoflagellates and ciliates. But in corals exposed to heatwaves, this balance shifts, with other microorganisms—some potentially harmful—becoming more dominant.

One of the biggest challenges for the team was figuring out how to study these microbes without interference from the coral’s own genetic material. To solve this, they designed special genetic primers that filtered out coral DNA, allowing them to get a clearer picture of how heat stress affects the coral’s microbial community. The study also suggests that these tiny organisms might be competing with or even preying on each other, further complicating how corals respond to heatwaves.

With Mediterranean waters getting hotter more often, understanding how these corals and their microbial partners react is more important than ever. The research highlights the urgent need to protect these ecosystems before climate change pushes them past the point of recovery.

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