The dive started on a flat bottom of moderately large manganese nodules covering a lighter-colored sediment primarily occupied by large hexactinellid sponges approximately 0.5 to 1 meter tall. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana. Download larger version (jpg, 1.6 MB).
A highlight of the midwater transects were the numerous larvacean houses observed, many with the original larvacean present. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana. Download larger version (jpg, 1.0 MB).
Dive 03: Sorceress Eel
This rarely seen sorceress eel was observed during Dive 03 to explore an unnamed seamount north of Johnston Atoll at a depth of ~2,400 meters (7,875 feet). Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana.. Download larger version (mp4, 29.0 MB).
Remotely operated vehicle Deep Discoverer (D2) arrived on a flat bottom of moderately large manganese nodules covering a lighter-colored sediment at 2,571 meters (~8,435 feet) depth. The area was primarily occupied by large hexactinellid sponges. We also observed a hermit crab with multiple zoanthids instead of a shell, smaller “goblet” sponges, and a black coral that had “cleaned” the organic detritus off the manganese nodules in a circle around it. As we moved further upslope, the substrate transitioned to a steeper, more consolidated rock that included manganese-crusted basalt pillows, boulders, and cemented sediment. Megafauna abundance increased – sea anemones and various corals, including chrysogorgiids, were observed. A crinoid was observed whose stalk was covered with hydroids and whose cup had what appeared to be a small eulimid snail attached, possibly parasitizing the crinoid. A second stalked crinoid displayed only four arms but had a eulimid snail attached onto the stump where the fifth arm was originally present. Other animals included a swimming sea cucumber as well as several ophiuroids. A potentially new sea cucumber with a translucent body wall was collected. A new record of Chyrsogorgia, which had been previously known from the East Pacific, was also collected along with its associates, including a squat lobster, amphipods, and several small polychaetes. A striking observation was the swimming/escape behavior from a black cerianthid tube anemone which D2 attempted to collect; it moved away from the manipulator arm. Following the end of the benthic segment of the dive, we undertook a set of midwater transects beginning at 800 meters (~2625 feet). A total of six transect depths was undertaken at 100-meter (~330-foot) intervals. We observed numerous larvacean houses, many with the original larvacean present. Other highlights included narcomedusae (genus Bathykorus), hydromedusae, and an opaque reddish jellyfish in the genus Periphyllopsis. Fish diversity included a hatchet fish, bristlemouths (Cyclothone) and a Sawtooth eel.