Ocean Acidification

Highlights

• Characterization of an unexplored CO₂ vent cave
• CO₂ vents chemical-physical parameters affect ecological traits of calcifiers
• Aphotoendosymbiotic solitary coral naturally inhabiting a CO₂-rich gas environment.
• Prolonged acidified conditions did not affect C. inornata growth rate
• Shift towards an r-demographic strategy in response to acidified conditions

Abstract

Submarine CO₂ volcanic vents represent peculiar environments with varying seawater chemical-physical parameters that may affect the ecological traits of calcifying organisms, such as growth and demographic characteristics. The present study focused on exploring the growth and population dynamics of a temperate, solitary and aphotoendosymbiotic coral Caryophyllia inornata (Duncan, 1878) living in a CO₂ vent cave at 14 m depth. The volcanic emissions in and around the cave led high levels of pCO₂, resulting in lower calcium carbonate saturation state (Ω_a: 2.1–2.2) values compared to those observed in the ambient seawater of the Mediterranean Sea, not affected by venting activity. Prolonged acidified conditions (pH_T: 7.5) did not affect C. inornata growth rate but resulted in a population with higher percentage of juvenile individuals, lower average ages and a lower age at maximum biomass percentage, thus suggesting a transition in its population dynamics towards an r-demographic strategy. This study provides a detailed characterization of a previously unexplored CO₂ vent cave, highlighting the importance of these sites as natural laboratories to offer valuable insights into understanding the full ecological impact of aphotoendosymbiotic corals under ocean acidification.

Cassarino C., Mancuso A., Prada F., Sani T., Dall’Ara S., Wallnoefer O., Marchini C., Tassi F., Campanelli A., Marini M., Hammel J. U., Kaandorp J. A., Falini G., Dubinsky Z., Caroselli E. & Goffredo S., 2025. Newly discovered CO₂ (carbon dioxide) vent cave drives r-strategy shift in a Mediterranean aphotoendosymbiotic coral. Science of the Total Environment 1005: 180858. doi: 10.1016/j.scitotenv.2025.180858. Article.