During the dive along a rift zone ridge extending west from Vogt Guyot, one of the presumed oldest seamounts on the Pacific Plate, scientists encountered some of the highest diversity of organisms of any dive on this leg of the expedition, from corals, crinoids, sea cucumbers, anemones, and sponges to fish, squat lobsters, and brittle stars. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download (mp4, 62.6 MB)
Today, remotely operated vehicle Deep Discoverer (D2) had a fantastic dive along a rift zone ridge extending west from Vogt Guyot, one of the presumed oldest seamounts on the Pacific Plate. This dive documented the highest biodiversity and general abundance of fauna of any of the other sites visited during this cruise. The seafloor was covered with thin sediment and large boulders covered with heavy manganese crusts. As D2 transited upslope, a few ledges projected out over the edge of the slope wall, and in a few places, fresh exposures of the sequences underneath the manganese coating were observed. These patches of outcrop were light in color, suggestive of reef material, as might be expected on the edge of the guyot summit. Throughout the dive, the majority of hard substrate was covered with corals, crinoids, sea cucumbers, anemones, and sponges. Corals observed included several different (and new) species of primnoids, isidids, chryosogorgiids, plexaurids, coralliids, black corals, cup corals, zoanthids, hydrozoans, and bamboo corals – some as big as one to two meters. Sponge populations were dominated by several species of hexactinellids. Closer to the slope edge, the density and composition of fauna increased even more, suggesting that the corals living on the edge of the ridge are better adapted to survive in stronger currents. Although not many fish were encountered, D2 recorded close-up imagery of a slick head (family Alepocephalidae) with parasitic isopods.