The project combined field research at natural CO2 vents with controlled laboratory experiments and molecular analyses. Although initially focused on Arbacia lixula, the scope was expanded to include the sympatric species Paracentrotus lividus, enabling comparative analyses and increasing ecological relevance. The project also incorporated adult microbiome analyses and temporal variation, broadening the assessment of host–microbiome interactions under acidification.
Three field expeditions were conducted to La Palma (Canary Islands), where natural pH gradients simulate future ocean scenarios. Experimental work was performed at the Observatorio Marino de Cambio Climático (OMACC), and molecular and bioinformatic analyses were carried out at the University of Barcelona.
The main achievements include:
Physiological responses and plasticity.
Respiration experiments demonstrated metabolic plasticity in both species under reduced pH. While short-term exposure triggered sharp increases in oxygen consumption—particularly in Arbacia lixula—individuals naturally inhabiting vent systems maintained respiration rates comparable to ambient populations, indicating long-term acclimatization or local adaptation and suggesting that natural pH variability may act as a physiological refuge.
Transcriptomic mechanisms of tolerance.
Genome-wide expression analyses revealed differential regulation of stress-response, ion-transport and metabolic pathways under acidification. Importantly, individuals from natural CO2 vent populations exhibited distinct baseline expression profiles compared to ambient populations, supporting evidence of local adaptation to chronically low pH conditions. Notably, A. lixula showed increased expression of genes associated with extracellular matrix organisation and collagen synthesis, suggesting alternative skeletal maintenance strategies under acidified environments. Transcriptomic studies for both species provide mechanistic insight into molecular buffering capacity and adaptive responses to long-term environmental change.
Microbiome dynamics across life stages.
Adult microbiomes displayed clear species-specific and site-dependent structuring in vent systems. Larval experiments showed that early microbial exposure significantly influenced survival patterns and developmental trajectories under acidification, with vent-associated microbiota promoting accelerated morphogenesis. Spatial and experimental analyses further revealed strong environmental and parental-origin effects on larval microbiome composition, highlighting both ecological structuring and plasticity.
Together, these results establish a multi-level framework linking physiology, gene expression and microbiome dynamics in shaping resilience to ocean acidification. Populations inhabiting natural CO2 vent systems displayed molecular and physiological signatures of tolerance to chronic low pH, indicating that they may represent important reservoirs of adaptive potential for future conservation planning.
