Dive 5: Virgin Islands Trough South Wall

Date: November 5, 2018
Location: Lat: 17.77290°, Lon: -64.42787°
Dive Depth Range: 1,890-2,153 meters (~6,200-7,065 feet)

Isopods, likely of the family Arcturidae, were observed on the bubblegum coral at a depth of about 1,950 meters (6,398 feet). Image courtesy of the NOAA Office of Ocean Exploration and Research, Exploring Deep-sea Habitats off Puerto Rico and the U.S. Virgin Islands. Download larger version (jpg, 1.0 MB).
The tripod fish, Ipnops murrayi, was only one of two species of fish observed during the dive. The prominent eyes of this species have been hypothesized to produce light; however, during an Okeanos Explorer expedition to the Gulf of Mexico earlier this year, the remotely operated vehicle's lights were turned off to see if its eyespots exhibited bioluminescence and they did not. Image courtesy of the NOAA Office of Ocean Exploration and Research, Exploring Deep-sea Habitats off Puerto Rico and the U.S. Virgin Islands. Download larger version (jpg, 1.2 MB).
A ceriantharian, also known as tube-dwelling anemone, filmed during Dive 5. In contrast to sea anemones, ceriantharians have two rings of tentacles with different tentacle lengths. The outer and longer ring of tentacles is used to capture food particles from the water column, while the inner and shorter ring of tentacles is used to move captured food particles towards the mouth. Image courtesy of the NOAA Office of Ocean Exploration and Research, Exploring Deep-sea Habitats off Puerto Rico and the U.S. Virgin Islands. Download larger version (jpg, 1.2 MB).
A carnivorous sponge (Chondrocladia sp.) seen towards the end of Dive 5. Image courtesy of the NOAA Office of Ocean Exploration and Research, Exploring Deep-sea Habitats off Puerto Rico and the U.S. Virgin Islands. Download larger version (jpg, 1.2 MB).

The fifth dive of the Océano Profundo 2018 expedition took us to the south wall of the Virgin Islands Trough. This is a near vertical feature that extends from depths of 2,000-4,000 meters (1.2-2.5 miles), and during the dive, we explored the near top portion of the wall at depths between 1,890-2,153 meters (~6,200-7,065 feet). During the first half of the dive, the habitat was dominated by soft sediments with scattered large boulders. In the second half of the dive, the terrain became much steeper with consolidated hardground. Sponges were by far the most common organisms during the dive and consisted mostly of glass sponges with some demosponges. Other invertebrates recorded during the dive included sea cucumbers, sea stars, crinoids, urchins, squat lobsters, as well as many different groups of corals including black corals, bubblegum corals, primnoids, chrysogorgids, and bamboo corals. We only observed two species of fish during the dive, including halosaurs (Aldrovandia sp.) and tripod fish (Ipnops murrayi). The dive also included the collection of three biological samples and one geological sample, several of which were collected under very challenging conditions, highlighting the superb skills of the remotely operated vehicle pilots.

The remotely operated vehicle Deep Discoverer is equipped with various devices for sampling water, rocks, and even animals from deep-sea habitats. While visual observation through the video is often a scientist’s primary tool, being able to collect samples from the deep seafloor is essential for getting a thorough understanding the object of interest. This might be analogous to seeing a really intriguing book cover versus being able to actually read the book and all its pages. Ocean exploration and conservation are carefully considered by our participating scientists, and every sample collection is carefully evaluated by experts who are able to provide input via telepresence.

Text contributed by Chris Mah, Smithsonian Institution, National Museum of Natural History.

Video courtesy of the NOAA Office of Ocean Exploration and Research, Exploring Deep-sea Habitats off Puerto Rico and the U.S. Virgin Islands. Download larger version (mp4, 65.7 MB).

Location of Dive 5 on November 5, 2018. Download larger version (jpg, 2.3 MB).

The remotely operated vehicle track for Dive 5, shown as a white line. Scale is water depth in meters. Download larger version (jpg, 237 KB).