Dive 08: “Pierpoint” Seamount
July 22, 2017
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Dive 08: Predatory Tunicates

This predatory tunicate was seen while exploring on "Pierpoint" Seamount. While we normally think of tunicates as being suspension feeders, this particular tunicate actually uses one of its siphons to trap small animals for food. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 Laulima O Ka Moana.. Download larger version (mp4, 28.2 MB).

At 1,600 meters (~5,250 feet) depth, the hard bottom was mostly covered by a lightly sedimented manganese crust. Fauna was relatively sparse throughout the dive. Octocorals appeared to be the dominant fauna and included chrysogorgiids, bamboo corals, primnoids, Victogorgia, a plexaurid, and bubblegum corals – most of the latter were overgrown with a yellow zoanthid. Black corals included Bathypathes, Stauropathes, Trissopathes, Alternatipathes, and a potential record of a juvenile unidentified schizopathid that was small and unbranched. Several soft corals were also observed. An unusual benthic, predatory jellyfish appeared on a moderately sized bamboo coral. Other benthic animals included several predatory tunicates, several species of stalked glass sponges, and stalked crinoids. Predation by sea stars was a highlight of the dive, with numerous observations of them feeding on corals. Other non-predatory asteroids seen on the substrate were a possibly new, red pedicellasterid, several individuals of Zoroaster sp., brisingids, and a few other goniasterids. Arthropods were not particularly abundant, but those observed included large stalked barnacles, a homolid crab, shrimps, several squat lobster commensals associated with octocorals, and a large sea spider. The only fishes observed were a few cutthroat eels.

A series of midwater transects began at a depth 800 meters (~2,625 feet). Midwater fauna observed included both pelagic metazoans and protists. Among the most abundant were siphonophores, colonial gelatinous hydrozoans, numerous medusae, comb jellies, and salps. Larvaceans and their mucous houses and arrow worms (chaetognaths) were observed with some frequency. Midwater fishes included a sawtooth eel, a slender fangjaw, and a hatchet fish.