Dive 10: West Florida Escarpment Bend
April 27, 2018
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Dive 10: Speed Star

This deep-sea mud star, Dytaster insignis, is a species which occurs in the true abyss, 2,515-3,530 meters (8,250-11,580 feet)! Although this individual was observed on the surface, it and other related “mud star” species are often seen buried just below the surface of muddy or sandy bottoms. This and related species are commonly collected with their disks engorged with mud. They have swallowed the sediment in order to devour potential snails and clams as well as other small organisms. Read the full caption. Video courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2018. Download larger version (mp4, 23.1 MB).

Dive 10 surveyed the biology and geology of the bend in the West Florida Escarpment. This area is completely unexplored, with the closest historical dive being conducted over 39 kilometers (~24 miles) away. Additionally, this dive targeted depths approaching 3,000 meters (~9,850 feet), which have been particularly poorly explored in the Gulf of Mexico. This was only the fifth scientific dive of close to 2,200 scientific dives that have been conducted in the Gulf of Mexico since the mid 1980s that explored these deeper depths.

Remotely operated vehicle Deep Discoverer (D2) reached the seafloor at a depth of 3,010 meters (9,875 feet) on a sediment-covered slope. Numerous species of sea star were observed at the beginning of the dive. Moving upslope, thinly layered carbonate rock was observed intermittently, suggesting a very thin sediment cover, which transitioned to outcrops of massive black ferromanganese-crusted carbonate rock. Rock outcrops were observed to have sessile organisms attached to the underside of the ledges, particularly encrusting sponges. Gradually, the carbonate rock outcrops transitioned into tan, thinly layered carbonate rocks interspersed with white colored, weak, eroded, carbonate rock that had been degraded by burrowing organisms. Further up the escarpment, the substrate was heavily weathered, and consisted of weak, white carbonate rock and sediment. Towards the end of the dive, D2 followed a sediment-covered ridge upslope with rock outcrops on either side of the ridge. Isolated corals and sponges were observed on the ridge crest.

The most commonly observed animals were sea cucumbers (Benthodytes sp.), long-legged shrimp (Nematocarcinus ensifer), and glass sponges (Hyalonema sp., Euplectellidae). Other species observed included tubeworms (Sabellidae), sea stars (Sibogaster sp., Hymenaster sp., Ampheraster alaminos), shrimp (Cerataspis sp., Mysidae), sea pens (Umbellula sp.), tube-dwelling anemones (Ceriantharians), anemones (Hormethiidae, unidentified Actinaria), squat lobsters (Galacantha sp., Munidopsidae), a predatory tunicate (Megalodicopia sp.), sea cucumbers (Deimatidae, Pseudostichopus sp.), bamboo corals (Keratoisis sp.), scleractinian cup corals (Caryophyllia sp.), chrysogorgid corals (Iridogorgia magnispiralis), and a single primnoid coral (unbranched Candidella sp.). The only fish observed during the dive were tripod fishes (Ipnops murrayi, Bathytyphlops sp.), and an unidentified cusk-eel (Ophididae) near the beginning of the dive.