Ocean acidification is one of the main stressors affecting marine ecosystems. Rare CO2 vents offer a unique opportunity to investigate the response of benthic ecosystems to acidification. However, the benthic habitats that have been investigated so far are mainly very shallow water (≤5 m depth) and, therefore, to habitats that are poorly representative of the broad range of habitats that occur on the continental shelf. Here, we show that a decrease from pH 8.1 to...