Atmospheric carbon dioxide enrichment alters seawater carbonate chemistry, thus threatening calcifying organisms such as corals. Coral populations at carbon dioxide vents are natural acidification experiments that mimic organism responses to seawater pH values projected for 2100.

This study investigated the demography and reproduction of populations of the solitary temperate coral Balanophyllia europaea naturally living along a pH gradient at a Mediterranean CO2 vent (Panarea, Italy).

It was found that gametogenesis and larval production were unaffected while recruitment efficiency collapsed at low and variable pH, contributing to coral abundance decline.

According to the obtained results, the authors propose early stages between larval production and recruit growth as coral Achille’s heel in an acidifying and warming ocean. It is stated that investigating these processes in coral populations naturally acclimated to ocean acidification and warming is required to clarify how the forthcoming seawater conditions will impact coral life history traits and the related ecosystem services they provide to human society.

Caroselli et al. (2018) Low and variable pH decreases recruitment efficiency in populations of a temperate coral naturally present at a CO2 vent. Limnology and Oceanography 9999:1-11.