This fish - potentially a Malacosarcus sp. - is a bit of a mystery for our science team as these prickelfish are usually found at shallower depths.

This fish - potentially a Malacosarcus sp. - is a bit of a mystery for our science team as these prickelfish are usually found at shallower depths. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download larger version (jpg, 264 KB).

Dive 21: Hadal Wall
July 8, 2016
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Day of the Dancing Cucumbers

During Dive 21, several different species of holothurians, or sea cucumbers, were documented dancing in the water column from every angle to enable accurate classification. One species, Enypniastes sp., is known to be bioluminescent, shedding their skin when attacked and rubbing that bioluminescence off on the attacker! Video courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas. Download (mp4, 159.8 MB)

Today's dive involved investigation of the western wall of the Mariana Trench at a site dubbed "Hadal Wall" to explore the transition between the abyssal and hadal zones and to document and characterize fauna on a diversity of habitat types. Deep Discoverer (D2) settled on a sedimented surface that was strewn with a few cobbles with dark to white surfaces. The seafloor had some channels that appeared eroded by debris either being removed by slumping or located between tongues of slumped debris. Most of the dive covered what appeared to be a talus slope with intermittent shallower slopes that were completely sedimented. D2 encountered primarily soft bottom fauna and evidence of past fauna including numerous spiral and zigzag trails of benthic animals on the sediment, several species of sea cucumbers and acorn worms, and areas where the sediment had a fluffy - potentially biotic- surface texture. Other fauna documented included a few sea stars; long-legged isopods walking along the seafloor; arrow worms; cusk eels (Penopus sp.); a ctenophore; small white drifting fish (potentially Malacosarcus); polychaete worms; and just above the bottom, a narcomedusa jellyfish. The dive concluded with a collection of a sunburst-shaped carnivorous sponge.