Ocean acidification (OA) will likely alter the bacterial community structure, disturb symbiotic relationships, and render the coral holobiont (the ecological unit formed by the coral and its associated microbiome) less resilient to disease. In the Azores region, the physiological responses of CWCs to different anthropogenic stressors have been studied using aquaria-based approaches at DeepSeaLab (Okeanos-UAç). Still, little is known about the effects of these stressors on the coral microbiome and how this modulates the physiological responses of corals. The CORHOLOA project aims to elucidate the roles of the microbes associated with two habitat forming octocorals in the Azores - Dentomuricea aff. meteor and Viminella flagellum - and their dynamic under scenarios of climate change and human pressures (ocean acidification and deep-sea mining). A DNA metagenomic approach was employed to examine the bacterial community structure associated with these two gorgonians, and further compared with the microbiome associated with the black coral Antipathella wollastonii and the scleractinian Eguchipsammia cornucopia.

Predicted changes in seawater chemistry resulting from climate change will affect all marine life, including the microbial dynamics and biogeochemical cycling in the ocean. In deep-sea ecosystems, cold-water corals (CWC) are bioengineer species considered vulnerable to such threats. Due to their heterotrophic feeding, broadly limited in nitrogen and carbon supply, these organisms rely on their microbial consortium to ensure their nutrition and health.