View from Seirios as remotely operated vehicle Deep Discoverer gets a closer look at a ferromanganese-encrusted outcrop.

View from Seirios as remotely operated vehicle Deep Discoverer gets a closer look at a ferromanganese-encrusted outcrop. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2017 American Samoa. Download larger version (jpg, 465 KB).

Close-up look at a holothurian sea cucumber reveals digestive tract full of sediment.

Close-up look at a holothurian sea cucumber reveals digestive tract full of sediment. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2017 American Samoa. Download larger version (jpg, 1.1 MB).

Dive 11: "Seamount D"
February 26, 2017
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Dive 11: Sampling on a Seamount

Analysis of samples collected during dives can help to give us a much better perspective on the evolution of life in the ocean. Video courtesy of the NOAA Office of Ocean Exploration and Research, 2017 American Samoa. Download (mp4, 23.2 MB)

During Dive 11, we explored "Seamount D," which lies in the eastern region of the Samoan Exclusive Economic Zone (EEZ). Seamounts located this far east in the Samoan EEZ had not been sampled prior to this expedition. Bathymetry collected during the expedition revealed the seamount to have a conical shape with a prominent ridge extending to the northwest. The dive began at a depth of ~3,000 meters, similar to depths reached during Dive 06 to explore on Utu Seamount, providing interesting comparison between the dives, as there were evident similarities in the benthic communities on both seamounts. Like at Utu Seamount, on Seamount D, we observed several species of octocorals, including chrysogorgiids (including Pleurogorgia and Iridogorgia), isidid bamboo corals, and whip and branching primnoids. We also saw numerous stalked and non-stalked sponges on large outcrops. Throughout most of the dive, the seafloor was composed of ferromanganese boulders and cobbles, with large outcrops, often with steep walls and overhangs. Geochemical analysis of rock samples collected during the dive can help to test the hypothesis that this seamount is an ancient volcano that formed by a different, non-Samoan hotspot.