On-board Diary: Ancient reefs and mules mobulas

Author: Silvia García
Date: August 18, 2013



It is 22:00 and we are sailing 70 mn to the SE of Formentera, towards one of the underwater canyons where we conducted an ROV immersion this morning. The ROV went on four dives today, reaching a total of 13 immersions and amounting to nearly 30 hours of footage of the seabed in the escarpment.

As with yesterday in Bel Guyot, today we found dead coral rubble at different points on the slopes, indicating that ancient reefs once lived in the shallower parts of these slopes. We caught some on camera, and they appear to be formed by ancient colonies of Dendrophyllia cornigera, the yellow tree coral. These habitats are very rich in species, as their three-dimensional structure is home to fish and crustaceans that find shelter in its nooks, as well as invertebrates that settle and develop directly on the branches of these corals.

It’s also worth mentioning that we saw devil rays again, this time jumping not far from our ship as we sailed. So in total there have been five sightings over the past few days at the escarpment, which is something to keep in mind when managing the species, which as we said yesterday, is protected in the Mediterranean. And finally, a group of at least 15 curious bottlenose dolphins, including a baby, approached us to take a look at the boat and maneuver around the ROV, so one of them appears on the screen a few meters below the surface when we first dropped the ROV into the water.