Match Made in the Deep
A brittle star clings to a glass sponge in a 'match made in the deep.' Being on the sponge puts the brittle star higher in the water column, where it can more easily grab food floating by. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download (mp4, 69.8 MB)
Dive 17 was conducted on a rift zone ridge extending southeast from Fryer Guyot, a Cretaceous seamount to the east of the Mariana Trench, to explore for deep-sea corals and sponges and to characterize one of the presumed oldest seamounts on the Pacific Plate. At the beginning of the dive, boulders appeared to be cemented to the seafloor and to one another by thick manganese coating. This area transitioned to an entirely flat seafloor and then to large and flat rock surrounded by ripple-marked sediment. There were scattered clumps of boulder- to cobble-sized rocks set among sediment ponds along the track for most of the dive. Many short vertical stumps, as well as broken, long stalks, of dead hexactinellid sponges coated with manganese suggests that the separating of the northern half of the plateau affected the fauna on the slope. Observed fauna included halosaurs; cusk eels; bubblegum coral; and numerous species of black corals, chyrsogorgiids, primnoids, bamboo corals, and sea pens. Other observations included zoanthids and anemones with their octocoral and sponge hosts, a "giant" tunicate, brittlestars (mostly on octocorals), crinoids, a couple of sea cucumbers, and seastars – including a brisingid growing four new arms. One of the biological samples today was likely the first collection from the Marianas of an aplacophora, rare shell-less mollusk coral predator!