Metabolic features of the deep-water coral Madrepora oculata were investigated, for specimens originating from about 800 m depth, in the Bay of Biscay (northeast Atlantic). Incubations of live specimens were carried out as a function of temperature (7, 10 and 13 °C), and for the first time as a function of hydrostatic pressure (atmospheric and natural pressures). An influence of temperature was observed, with about 40% reduction of oxygen consumption at a temperature cooler than in situ, but no obvious increase in a warmer experimental environment. CO2 production increased upon warming from 7°C to 13°C. Hydrostatic pressure had a significant influence on ammonium excretion (and on O:N ratio), suggesting a stress response following exposure to atmospheric pressure. It is the first time that such a response to pressure variation is observed, calling for increased attention towards pressure effects on live deep-water corals. According to the expected shoaling of aragonite saturation horizon, studies of deeper-living samples, situated at the lower boundary of their natural depth distribution, appear necessary to better understand the impact of ocean acidification on reef-building scleractinian corals. The present work shows that some biological features are pressure-sensitive, and suggests that investigations on such corals should be undertaken at in situ pressure.
Shillito et al. (Fri,) studied this question.