Dive 12: Mona Canyon East Wall
Date: November 12, 2018
Location: Lat: 18.54352°, Lon: -67.29510°
Dive Depth Range: 1,966-2,415 meters (6,450-7,925 feet)


Today’s dive took us to depths between 1,966-2,415 meters (6,450-7,925 feet) on a steep ridge on the eastern side of the Mona Canyon, an area of the canyon that had never before been explored with remotely operated vehicles. The dive started off in soft sediments and then transitioned into jagged rock outcrops, which were interestingly not covered with iron manganese. Currents were consistently strong throughout the dive and flowing from north to south.

The fauna on this part of Mona Canyon was sparse. We only recorded three species of fish, including cusk eels (Barathrodenus manatinus), halosaurs (Aldrovandia sp.), and tripod fish (Ipnops murrayi). Deep-sea sponges and corals were similarly sparse and consisted mostly of glass sponges, encrusting demosponges, cladorhizid demosponges, the primnoid coral Candidella imbricata, and a branched bamboo coral. Echinoderms were once again the most abundant group of animals on today’s dive, with sea cucumbers and brittle stars being the most common ones. Other echinoderms we recorded included two species of urchins, two species of crinoids, and three species of sea stars, including brisingid sea stars, which were quite common throughout the dive.

A notable observation from the dive was a strange mollusc in the soft sediment that looked like a small white snail with its foot extended. We also recorded quite a few shrimps on today’s dive, both sitting on the seafloor as well as swimming through the water column.

Mona Canyon is an approximately 140-kilometer long, 30 kilometer-wide, and 4 kilometer-high submarine canyon located off the northwest coast of Puerto Rico. Geologists have been studying this canyon using mapping data for quite some time, but it was not until 2013 when the first visual surveys of Mona Canyon were conducted by the E/V Nautilus using their remotely operated vehicle (ROV) Hercules. At the time, two dives took place to maximum depths of 1,975 meters (6,480 feet) and 2,832 meters (9,291 feet), respectively, to conduct the first visual characterization of the geology of the canyon. Given the enormous size of the canyon, and the broad interest by the scientific community to further explore this feature, NOAA Ship Okeanos Explorer conducted two additional ROV dives in Mona Canyon in 2015, to maximum depths of 3,928 meters (12,887 feet) and 4,025 meters (13,205 feet), respectively. These dives built on the previous dives from 2013, and added important biological observations within the canyon.

When NOAA Ship Okeanos Explorer returned to this region in 2018, there was once again interest from both biologists and geologists alike to further explore, sample, and survey Mona Canyon. Dive 12 of the Océano Profundo 2018 expedition explored the eastern wall of Mona Canyon, a very steep feature that had not been previously explored.

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, 51.2 MB).

 


 

Location of Dive 12 on November 12, 2018.

Location of Dive 12 on November 12, 2018. Download larger version (jpg, 2.2 MB).

The remotely operated vehicle track for Dive 12, shown as a white line. Scale is water depth in meters.

The remotely operated vehicle track for Dive 12, shown as a white line. Scale is water depth in meters. Download larger version (jpg, 316 KB).