Dive 14: Escarpment Canyon Ridge
May 1, 2018
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Dive 14: The Gulf’s Secret Garden

Towards the end of Dive 14, we came upon a dense bamboo coral garden at approximately 2,300 meters (~7,545 feet) deep. This was exciting because we had not previously seen such a dense community at this depth in this area before. The dramatic ridge crest appeared to provide ideal conditions for these corals, whose fans were lined up to take advantage of the currents. These corals were likely hundreds, if not over a thousand, years old. The science team notes that to have a high-density community like this, a lot of factors needed to come together, including the right underlying geology, current flow, food availability, coral recruitment, and stability. Download larger version (mp4, 43.5 MB).

Today’s dive surveyed an unexplored narrow ridge feature off a system of canyons on the southern end of the West Florida Escarpment to a depth of ~2,400 meters (~7,875 feet). On the ridge crest, there were several exposed rocks, but no encrusting organisms were seen growing on them. However, moving up the ridge crest, numerous exposed rocks and boulders hosted corals and sponges. For most of the dive, large rock outcrops, separated by sediment patches, were observed. Corals and sponges, as well as densely clumped communities of associated invertebrates, were more common on the rocks than in the sedimented areas. Some rocks displayed clear layering and most had a black oxide crust. In one area, pronounced scour pits around some rocks were observed, indicating excavation by rapid currents. Towards the later part of the dive, the terrain became steeper and vertical rock walls were observed. Additionally, the ridge crest became very narrow – only a few meters across.

The most commonly encountered animals included bamboo corals, black corals, plexaurid corals, and glass sponges. Other animals included chrysogorgid corals, precious coral, stoloniferan corals, anthothelid corals, sea pens, anemones, demosponges, sea stars, zoanthids, crinoids, bryozoans, benthic ctenophores, barnacles, shrimp, and a sea cucumber. Fish included tripod fishes, halosaurs, and a cusk eel. Towards the end of the dive, we observed a very high density of bamboo corals and glass sponges; these are among the deepest high-density communities ever recorded in the Gulf of Mexico.