Dive 05: "Sally" Seamount
July 17, 2017
Access Dive Summary and ROV Data
Loading the player...

Dive 05: Deep-sea Scale Worm

While exploring the north ridge of a guyot-like feature at 2,170 meters (~7,120 feet) depth, scientists were surprised to see this scale worm, which measured nearly 10 centimeters (four inches) long, as they had not seen a scale worm this large in such shallow water. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana.. Download larger version (mp4, 23.3 MB).

Today, Deep Discoverer explored the north ridge of a guyot-like feature, traversing to its plateau. The dive began at a depth of approximately 2,170 meters (~7,120 feet) on manganese-encrusted rocky substrate with light colored sediment. We observed numerous dead bamboo coral and glass sponge skeletons, prompting a discussion of whether this was natural mortality or a catastrophic event. Numerous octocorals (primnoids, bamboo corals, and Chrysogorgiids) and black corals were encountered throughout the survey region. Several large, well-developed, older-looking bamboo corals formed moderately abundant patches on elevated mounds of pillow lava. Two aplacophorans, worm-like mollusks, were observed on the barren areas, suggesting predation, whereas elsewhere on the colony, benthic ctenophores were perched, passively fishing for zooplankton. Several unidentified species of cup corals were also documented. Potential new species of bamboo and black coral were collected. Many species of moderate to large-sized glass sponges were documented, and one unusual glass sponge was collected. Echinoderms included a large Henricia sea star, several brittle stars, a swimming sea cucumber, a juvenile transparent slime star, one sea urchin, and several species of feather stars. A small individual feather star displayed a disproportionately large eulimid snail. Other invertebrates included the long-legged shrimp and a swimming large purple polychaete. Fishes observed on the benthic portion of the dive were few and included an unidentified grenadier and a cusk eel.

Midwater surveys were conducted during ascent, starting at a depth of 900 meters (~2,950 feet). Among the most striking of the midwater animals encountered was an undescribed comb jelly, a bristle mouth fish, a swimming cusk eel, several vertically positioned sawtooth eels, and a hatchet fish. Other interesting observations included larvacean houses and a bizarre three- to four-armed glassine protist, numerous hydrozoan jellyfish, a hyperiid amphipod, and several salps.