Modelling the Habitat Distribution of the Endemic Azooxanthellate Coral <scp><i>Madracis interjecta</i></scp> From the Mesophotic to the Deep Red Sea

The coral genus <i>Madracis</i> has a global distribution from shallow waters to over 1200 m depth. In the Red Sea, the azooxanthellate endemic species <i>Madracis interjecta</i> is known to occur from depths of 120 to 350 m. This species is often observed in mesophotic ecosystems and has been reported to form sediment-binding bioherms, yet the conditions required for these formations are not understood. Here, we extracted quantitative data from video footage to identify the distribution of <i>M. interjecta</i> for the first time along the Saudi Arabian Red Sea coast. We present a habitat suitability model to identify potential habitats in the northern Red Sea and Gulf of Aqaba for this species. Combining presence data with geomorphometric variables and environmental data, we identified both depth and seafloor ruggedness as main drivers of this species distribution. Through multivariate statistics, we found that bioherms were found in deeper and cooler waters than individual <i>M. interjecta</i> colonies. Due to the narrow continental shelf and steep slopes of the northern Red Sea and Gulf of Aqaba, the effects of coastal development are threatening shallow, mesophotic and deep ecosystems. This work provides both a baseline survey and predicted distributions of an important habitat-forming scleractinian coral, which can inform conservation planning in the region.