High pCO2 habitats and their populations provide an unparalleled opportunity to assess how species may survive under future ocean acidification conditions, and help to reveal the traits that confer tolerance.

This paper utilized a unique CO2 vent system (Ischia Island, Italy) to study the effects of exposure to elevated pCO2 on trait-shifts observed throughout natural populations of Astroides calycularis, an azooxanthellate scleractinian coral endemic to the Mediterranean Sea.

The authors found unexpected shifts in skeletal and growth patterns. Colonies shifted to a skeletal phenotype characterized by encrusting morphology, smaller size, reduced coenosarc tissue, fewer polyps, and less porous and denser skeletons at low pH. The transcriptomic data revealed as well strong genetic differentiation among local populations of this warm water species whose distribution range is currently expanding northward.

The authors conclude that the results demonstrate how coral populations can persist in high pCO2 environments, making this system a powerful candidate for investigating acclimatization and local adaptation of organisms to global environmental change.

https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15372

Teixidó et al. (2020) Ocean acidification causes variable trait-shifts in a coral species. Global Change Biology DOI: 10.1111/gcb.15372.