Mario Fernandez, Casey Machado, Tim Shank, and Santiago Herrera (left to right) in the Nereus control room during an 8-hour dive to 6,000 meters. Photo by Ken Kostel, Woods Hole Oceanographic Institution.
This week, Nereus made dives of increasing depth along the axis of the Kermadec Trench and has so far spent roughly 24 hours on the seafloor. At 6,000 meters, the vehicle collected push cores for sediment, microfauna, and macrofauna analysis and ran imaging transects; at 7,000 meters, the team deployed the respirometer, collected macrofauna samples and push cores, and conducted imaging transects.
The terrain of the seafloor seen so far has been varied, ranging from sediment ponds to steep cliffs, from fine-grained sediment to loose gravel to boulders, and from carbonate chalk to basalt to highly altered rock. The diversity of seafloor structure underscores the wide range in community structure as well as the abundance and diversity of the organisms that have been documented just between 6,000 and 7,000 meters on Nereus transects and deployments of the hadal and abyssal lander and fish trap. Specimens of roughly two dozen species have been collected so far and more than twice that recorded on transects and lander images.
A few highlights of animals brought back to the surface include seven different species of fish overall, including nine snailfish; nearly one dozen amphipod morphs plus a super-giant amphipod; three different shrimp species; and a variety of isopods, gastropods, crinoids, and other organisms. A half-dozen water samples and two dozen push cores have been filtered or sampled for microbial genomic analysis and there are already roughly 20 high-pressure cultures prepared.