On-board Diary: Old reefs north of the seamount
Author: Silvia García
Date: July 8, 2011
Because of the wind yesterday, we have a strong swell when we set sail to the seamount, but it won’t be a problem because the weather forecast for today is good, so we count on the conditions improving throughout the day.
We reach today’s first study area around 9:00, the northern slope of the main seamount. A little before 10:00, we submerge the ROV and it reaches the bottom in 10 minutes, at 124 meters. The sea bed is quite flat and the most interesting thing is the almost continuous presence of Pteroides spinulosum and Pennatula rubra sea pens. For the second dive, also on the northern slope but a little more toward the east, we head NE starting at 195 meters and descending to 315 meters. The bottom is completely detritic and the most interesting thing is some small solitary corals on the sea bed, possibly Sphenotrochus andrewianus, and we observe various specimens during the dive. We also observed various goose foot starfish Anseropoda placenta. Last, we dove off some mounts NE of the main seamount. We began at the peak of one of them, at 250 meters and continued down to 326 meters constantly documenting the rocky slopes and walls, including some caves. This area is full of dead coral, in the shape of reefs that are quite large, or lying on the flat sea bed. It could be Madrepora occulata and Dendrophyllia cornigera, because we found some live colonies of both species growing on these very remnants, but few compared to the number of skeletons. In addition, we identified a cup sponge Asconema setubalense next to the base and we documented a beautiful live colony of Lophelia pertusa.
During this last dive, we filmed numerous small sponges that appear constantly, both on the flat bed and on rocky walls, and we took samples of one of them using the ROV’s arm. We know it's a desmospongiae, but we're not sure right now what species it is.