Dive 3: South of Pioneer Bank
March 2, 2016
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Sea Cucumber

Swimming sea cucumber seen on March 2, 2016, on a rift zone ridge extending to the south of Pioneer Bank at a depth of ~2,300 meters. Video courtesy of the NOAA Office of Ocean Exploration and Research, Deepwater Wonders of Wake.

Dive 3 was conducted on a rift zone ridge extending to the south of Pioneer Bank. Previous dives on the ridge have been conducted by both the Okeanos Explorer in 2015 (maximum depth of 2,119 meters) and the Hawaii Undersea Research Laboratory in 2003 (maximum depth of 1,813 and 1,825 meters). These dives documented one of the largest communities of deep-sea corals and sponges in the Monument. This high-density community extends for at least five miles at depths ranging between 1,800-2,100 meters along the top of the ridge. The objective of this dive was to survey the area below previous dives on the ridge in order to determine the lower depth limit of the high-density community. The target start point of the dive was approximately five miles south of the dive conducted on Pioneer Bank Ridge by the Okeanos Explorer in 2015.

The remotely operated vehicle (ROV) landed on the ridge crest at a depth of 2,352 meters. The bottom consisted of intact pillow lava flows and interspersed volcanic rubble with light sedimentation. The volcanic flows and rubble were covered with a moderate density of corals and sponges. As the ROV moved north along the ridge crest, the density of animals remained moderate and consisted mainly of primnoid and black corals, with scattered anemones and crinoids. The majority of corals and sponges were very small in size. A rock sample was collected at a depth of 2,353 meters which had hydoids growing it. Along the transit up the ridge, multiple local highs were interpreted as vent sources for proximal intact pillow lava flows. These elevated structures supported noticeable higher densities of organisms, and consisted mainly of small primnoid colonies. At 2,331 meters, the ROV collected coral specimens of both a Chrysogorgia sp. and a Pleurocorallium sp. colony that were right next to each other. As the ROV continued to move along the ridge crest, the densities of animals remained moderate to high. The ROV left the bottom at a depth of 2,343 meters.