Purple ctenophore, possibly Lampocteis cruentiventer, imaged at 1,000 meters during today’s water column transects. Not all ctenophores are pelagic – some are benthic, living near the seafloor. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2015 Hohonu Moana. Download larger version (jpg, 1.2 MB).
Dive 12 of the expedition was conducted today along the western edge of a rift zone ridge extending southeast from Pearl & Hermes Atoll. The objectives of the dive were to explore for high-density communities of deep-sea corals and sponges along the edge of the ridge crest, to obtain information on the lower depth range of these communities, and to document nekton and gelatinous megaplankton in the water column during the ascent to the surface. The dive started close to a wall with manganese-crusted pillow basalts and several stalked sponges at 2,790 meters. As the ROV moved towards the edge of the wall, there was a small aggregation of stalked sponges and corals. The ROV then moved along the edge of the wall towards the northwest, where the pillow basalts became distinctly round and covered with a high density of barnacles. As the ROV continued moving along the edge of the wall, several narrow canyons, one to two meters in width, were observed. The ROV left the bottom at a depth of 2,773 meters and proceeded to 1,200 meters to conduct the first mid-water transects of the expedition. Mid-water transects were conducted for 10 minutes each at 1,200 meters, 1,000 meters, 800 meters, 600 meters and 450 meters. A few animals were observed during the mid-water transects, including jellyfishes, ctenophores, siphonophores, shrimps, fishes, salps, and a squid.