Dive 8: La Parguera Ridges
Date: November 8, 2018
Location: Lat: 17.85197°, Lon: -67.05533°
Dive Depth Range: 804-1,101 meters (2,635-3,610 feet)


Today’s dive took us to an unexplored ridge off La Parguera on the southwestern shore of Puerto Rico. During this dive, we climbed a gentle slope from depths of 1,101-804 meters (3,610-2,635 feet), which was dominated mostly by soft sediments, a habitat that we had not yet explored in detail during the Océano Profundo 2018 expedition. Consequently, we documented several species that we had not yet recorded on this mission.

Deep-sea corals and sponges were neither abundant nor diverse at the site and consisted mostly of sea pens and a few glass sponges. Even though the terrain did not include many structural features, we observed a good number of different fishes, 13 species in total. The most common among these were cusk eels (possibly Dicrolene sp.) and halosaurs (Aldrovandia sp.). Echinoderms were the most abundant and diverse group of animals observed on this dive and included several species of sea cucumbers, crinoids, urchins, and a sea star.

Interestingly, we observed several pieces of wood fall on this dive with various attached invertebrates, as well as a single colony of the scleractinian coral Madrepora oculata growing on the soft bottom. Samples of both of these were collected, as well as of a seapen.

360-degree feeding. With tentacles extended in all directions, the Rhopalonematid jelly Crossota millsae is caught in a very interesting natural pose by the remotely operated vehicle (ROV) Deep Discoverer’s cameras in waters south of La Parguera on the southwestern shore of Puerto Rico at a depth of 1,015 meters (3,330 feet). Moving just above the seafloor, ROV Deep Discoverer came across this jellyfish hovering with its tentacles extending outward in all directions. Looking into known accounts of jellyfish similar to this one, it appears the jellyfish shown is a male individual of Crossota millsae, a jellyfish in the Family Rhopalonematidae.

This is not the first time we have encountered a specimen like this – other species in this family of jellies have been caught by our ROV’s cameras. Certainly psychedelic, the video shows a jelly in a very interesting pose, suggesting this jellyfish may feed by hovering above the seafloor with stinging cell-loaded tentacles extended and waiting for prey. In other dives, these poses were followed by rapid swimming. Known from the Atlantic as well as the Pacific, jellies similar to these have been found not too far from the seafloor, suggesting a linkage between the benthos and the water column. Recording seemingly natural behaviors and stances by deep-ocean life in high-definition has given us the ability to not only identify these organisms, but learn a little about how they live.

Text contributed by Mike Ford, NOAA National Marine Fisheries Service and Smithsonian Environmental Research Center.

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, 66.7 MB).

 


 

Location of Dive 8 on November 8, 2018.

Location of Dive 8 on November 8, 2018. Download larger version (jpg, 2.2 MB).

The remotely operated vehicle track for Dive 8, shown as a white line. Scale is water depth in meters.

The remotely operated vehicle track for Dive 8, shown as a white line. Scale is water depth in meters. Download larger version (jpg, 174 KB).