DEEPLIFE in Science of the Total Environment (2022)

An understanding of all components of coral ecosystems is essential to predict effects of global warming. Antipatharians, also called black corals, are components of mesophotic coral ecosystems (MCE). Antipatharians are present in almost all oceans of the world and their abundance reach a peak at mesophotic depths. Antipatharians can play a key role in MCE by forming black coral forests, which act as spawning, nursery and feeding areas that support diverse animal communities, and create biodiversity hotspots.

The collaboration between UNDER THE POLE, the Université Libre de Bruxelles, and the French National Centre for Scientific Research (CNRS) allowed to fill the gap of knowledge on black coral sensibility to global warming. We provided the first assessment on the susceptibility of black coral to thermal stress, by working on the mesophotic antipatharian Stichopathes sp. from Mo’orea (French Polynesia).

Sampling was carried out between 70 and 90 m depth by technical divers from UNDER THE POLE. Corals were installed in 200 L-aquaria to be exposed to four temperature treatments (26°C control temperature, 27.5°C, 29°C and 30.5°C) through a 16-d laboratory exposure. To assess their physiological capability to cope with heat stress, metabolic, biochemical, and cellular responses of corals were determined.

The optimal temperature, i.e. allowing the black coral Stichopathes sp. to efficiently perform its biological functions, was determined around 28.3 °C. The first signs of stress were observed around 29°C, revealing a narrow thermal window of performance for this coral. These results suggest that black corals have poor thermal acclimatization capacity. A 1°C increase could have significant consequences for this foundation species.

Summary from the article "Thermal stress responses of the antipatharian Stichopathes sp. from the mesophotic reef of Mo'orea, French Polynesia."

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Authors - Godefroid M., Hédouin L., Mercière A., Under The Pole Consortium, Dubois P.