# Climate stress is degrading Mediterranean ‘false coral’ habitats, study warns
*Mediterranean ‘false coral’ shows how a hotter, more acidic ocean can unbuild underwater cities.*
A Spanish‑led team reports that Mediterranean bryozoans—colonial invertebrates known as ‘false coral’—are being reshaped by climate change. Working at natural CO₂ vents off Ischia, Italy, the scientists found that acidification and warming together alter skeleton structure and the resident microbiome, reducing habitat cover and increasing mortality.
“these small architects of the sea are often overlooked,” said lead author Blanca Figuerola. Another co‑author added: “Even if colonies look externally healthy, changes in the microbiome could serve as early bioindicators of environmental stress,” Javier del Campo said.
## What are bryozoans and why they matter
Bryozoans build hard, three‑dimensional colonies that shelter other species. In the Mediterranean, Myriapora truncata (‘false coral’) can form reef‑like systems. Their decline would ripple through food webs that rely on these habitats.
## A natural lab off Ischia
Volcanic CO₂ bubbles near Ischia recreate end‑century acidification in the wild. The team compared exposed and unexposed colonies and tracked warming effects over five years, capturing how the two stressors interact.
## What the study found
Under high CO₂, colonies tweaked their skeleton mineralogy and kept a broadly similar set of microbes, but lost important microbial functions tied to nutrition and defence. When warming was added, coverage dropped and mortality rose. Imaging with computed microtomography revealed internal skeletal changes that routine inspections can miss.
## Why it matters now
Subtle microbiome shifts can warn of trouble before colonies visibly fail. The authors say these results should inform conservation across a warming, acidifying Mediterranean, where safeguarding habitat builders helps protect wider marine life.
### Takeaway
Climate stress is not just bleaching corals—it is quietly unbuilding other marine fortresses. Spotting early microbial warnings could buy time for targeted protection.
[Read the original study summary on ScienceDaily](https://www.sciencedaily.com/releases/2025/08/250814094700.htm).