2026 Cook Islands ROV Exploration
Dive 07: Sawtooth Abyss (Take 2)
Dive 07 took place on “Sawtooth Abyss,” an abyssal plain within a few kilometers of the boundary between the Cook Islands and American Samoa. We had planned to dive on this feature, so named due its the sawtooth appearance in collected mapping data, two days ago, but encountered issues with the remotely operated vehicle before reaching the seafloor. During the seventh cruise dive, which started at a depth of approximately 5,700 meters (3.5 miles), the team was able to document the presence of polymetallic nodules on the seafloor of this abyssal plain, though the nodules were more angular and irregular in shape and size than nodules encountered during previous dives. The nodules were also more spaced and less dense than seen on previous dives and they were interspersed with manganese encrusted rocks and shark teeth ranging from 6 to 16 centimeters (2.4 to 6.3 inches) in length. Marine life was sparsely distributed, which is not unusual at abyssal depths. We observed a variety of invertebrates, including a few different species of sea cucumbers, crinoids, an acorn worm, a brisingid seastar, as well as a cusk eel. When D2 completed a dive in 2017 at similar depths southwest of the Phoenix Islands, the team encountered similar creatures.
Acorn worms, like this one seen during Dive 07 of the 2026 Cook Islands ROV Exploration cruise, are bottom-dwelling invertebrates that create distinct spiral patterns on the seafloor as they ingest mud, process nutrients from it, and leave a spiral of waste behind them. We saw these coiled waste piles through the dive. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 1 MB).
This shark tooth, collected during Dive 07 of the 2026 Cook Islands ROV Exploration cruise, measured 11.5 centimeters (4.5 inches) across! Throughout the dive the team observed these large shark teeth on the seafloor, amongst angular polymetallic nodules and manganese-coated rocks. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 809 KB).
Angular, irregularly shaped polymetallic nodules of various sizes were observed on the seafloor of the abyssal plain explored during Dive 07 of the 2026 Cook Islands ROV Exploration cruise. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 926 KB).
A brisingid sea star, Freyellaster sp., extends its arms into the water column. It was one of three biological samples collected during Dive 07 of the 2026 Cook Islands ROV Exploration cruise. Image courtesy of NOAA Ocean Exploration, 2026 Cook Islands ROV Exploration. Download largest version (jpg, 963 KB).