Distribution of sea urchins living near shallow water CO₂ vents is dependent upon species acid-base and ion-regulatory abilities

To reduce the negative effect of climate change on Biodiversity, the use of geological CO₂ sequestration has been proposed; however leakage from underwater storages may represent a risk to marine life. As extracellular homeostasis is important in determining species' ability to cope with elevated CO₂, we investigated the acid-base and ion regulatory responses, as well as the density, of sea urchins living around CO₂ vents at Vulcano, Italy. We conducted in situ transplantation and field-based laboratory exposures to different pCO₂/pH regimes. Our results confirm that sea urchins have some ability to regulate their extracellular fluid under elevated pCO₂. Furthermore, we show that even in closely-related taxa divergent physiological capabilities underlie differences in taxa distribution around the CO₂ vent. It is concluded that species distribution under the sort of elevated CO₂ conditions occurring with leakages from geological storages and future ocean acidification scenarios, may partly be determined by quite subtle physiological differentiation.