Sponges and echinoderms were the main fauna observed during Dive 14. 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).
Crinoids were more abundant during Dive 14 than at any other site explored during the expedition. They were frequently seen close to the edges of ledges. 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).
Yellowfish flagfish Aulopus filametosus seen during Dive 14. This is the first time we have encountered this species on this expedition. Fishermen targeting deepwater snappers and groupers report frequently catching this species. 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, 1.5 MB).
The distinctive Halopus sp. crinoid was commonly encountered during the dive. 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, 1.3 MB).
During today’s dive, we explored a submarine bank north of Bajo de Sico in the Mona Passage. The dive started on a flat hard substrate that was covered by a thin veneer of sediment. The substrate was broken in a stepwise fashion with sand channels dividing the steps. Sand ripples were seen in these channels, indicating the presence of high currents in a consistent direction at the site.
Sponges and echinoderms were the main fauna on the seafloor. Small individuals of a variety of different demosponges and glass sponges were in high abundance and scattered all over the seafloor. Echinoderms were also quite diverse and included at least three species of sea stars, three species of sea urchins, two species of sea cucumbers, and two species of crinoids. Particularly noteworthy was the abundance of crinoids, as we saw more crinoids than on any of our previous dives of this expedition, often on the edge of ledges.
Deep-sea corals were poorly represented at this site, with only a few colonies of black corals, scleractinian corals, primnoids, and soft corals. Fish were also not very abundant nor diverse, with only seven fish species recorded. We did, however, see a fish that was a new record for this expedition, the yellowfish flagfish Aulopus filametosus. Fishermen targeting deepwater snappers and groupers in this area reported catching this species. Only one small individual of the queen snapper was seen during the dive. Interestingly, we did encounter several boarfish (Antigonia sp.), and fishermen noted that queen snappers do not like to go near boarfish because the boarfish will not let the queen snappers feed.
We also recorded several anemones, shrimp, squat lobsters, and crabs, the latter two of which were frequently seen inside cracks and crevices. Furthermore, we also saw some fishing line and fishing weights on the seafloor.
Dive 14 explored seafloor habitats at 319-398 meters (1,047-1,306 feet), and the dive site was marked by a striking diversity and density of sponges, particularly of those known as glass sponges (class Hexactinellida) and rock sponges (Lithistid demosponges). These two groups of sponges are very ancient and are known to have been major reef-builders throughout the Paleozoic and Mesozoic Eras (65-542 millions years ago). At present, these sponges are mostly found in deep waters (below 200 meters or 656 feet), as only a few representatives of these groups occur in shallower depths, where they are typically found inside caves.
Text contributed by Joana Xavier, University of Bergen.
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, 76.4 MB).
