Dive 12: Mussorgsky Seamount
September 18, 2017
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Dive 12: Munchies

During the dive on Mussorgsky Seamount, the Okeanos team encountered this crab which appeared to be eating a sponge. The structural elements of most sponges are made of silica, the same material glass is made of, so a sponge doesn't seem like a tasty, or highly digestible, choice for a meal. Video courtesy of the NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. Download (mp4, 23.1 MB)

Dive 12 targeted a ridge feature atop Mussorgsky Seamount. This seamount is the most isolated in the Musicians Seamounts, in terms of distance from another large ridge feature or seamount. Remotely operated vehicle Deep Discoverer (D2) arrived on bottom at 2,059 meters (6,755 feet) in a geological setting that included intact pillow flows, some cobbles, and large sponges. Numerous coral colonies soon came into view at the start of the high-density community discovered along the summit ridge. D2 transited upslope and the team documented several small, and rare brittlestars (Asterophiura sp.) that mimic sea stars and observed intact low relief lumpy pillow flows, alternating with talus chutes. As D2 moved south along the ridge crest, the team observed large pillow lobes as the sponge and coral community continued. Corals observed included precious coral (Hemicorallium sp.), bamboo corals, cup corals, and an abundance of primnoids and chrysogorgid corals. Further upslope, larger outcrops and blocks appeared and were covered in corals and sponges. As large broken slabs alternated with sheet/lobate flows, the same or higher density and abundance of corals persisted. Low relief lava flows, some with obvious edges, and moderate sediment cover were observed at 1,980 meters (6,496 feet). Here, primnoid and bamboo corals abounded. Low relief flows continued up the slope with little talus and occasional flow fronts/edges exposed. The summit was nearly flat (1,957 meters; 6,420 feet) and was composed of a mix of low relief pillows, talus, and sediment, with many corals, but no sponges. Other biological observations during the dive included a codling fish, brittle stars, an orange Nemertean ribbon worm, squat lobsters, eels, shrimp, a chiton, crinoids, sea stars, a couple of crabs, and anemones.