Today marked our first midwater dive of the expedition, and we were fortunate to have various midwater specialists join us on the line from shore to help guide the dive. Our dive site was located just north of Bear Seamount, within the Northeast Canyons and Seamounts Marine National Monument. There have been extensive nekton trawling surveys in the vicinity of this site, as well as several remotely operated vehicle (ROV) dives that explored benthic habitats on Bear Seamount. However, there had been no previous midwater ROV dives on the seamount. This dive therefore sought to collect valuable midwater video data for comparisons to historic midwater trawl data.
We began this dive by descending towards the seafloor, at a depth of 2,182 meters (~7,159 feet) and performing two near bottom transects at 1.5 meters (~5 feet) and 10 meters (~33 feet) above the seafloor. Particulates in the water column were dense during these transects, and numerous larvacean houses were observed along with ctenophores, arrow worms, krill, hydromedusae, and copepods. A large chimera and juvenile rattail fish were also observed just above the seafloor. Between transects, a possibly new species of red cidippid ctenophore was collected using the suction sampler.
Today we dove on the southern wall of an unnamed minor canyon north of Kinlan Canyon. Major shelf-incised canyons in this region have received a fair amount of attention in terms of exploration; however, minor slope canyons like the one targeted during this dive remain mostly unexplored. The planned dive track was designed to cross the canyon axis in order to assess the geologically recent sediment transport history of the canyon, as well as the benthic communities of the area.
The remotely operated vehicle (ROV) reached the seafloor near the northern wall on the canyon, where the current was relatively swift. The floor of the canyon was predominantly soft sediment, with a similar biological assemblage as that observed at the Dive 03 site, composed of quill worms, lantern sharks, schools of fin squid, and deep-sea red crabs. Several clumps of Lophelia pertusa skeleton were observed in the bottom of the canyon with sediment displaced around them, suggesting that they fell off the northern canyon wall, but no living specimens were observed. As we traveled across the canyon axis, we observed abundant evidence of slope failure in the form of large boulders, which hosted sponges, cup corals, plexaurid corals, and Venus flytrap anemones. Upon reaching the southern wall of the canyon, we discovered sheer walls of sandstone and limestone heavily encrusted with corals, sponges, and other invertebrates. We documented three large specimens of Atlantic Halibut, an endangered species. The planned ascent up the southern canyon wall was halted to evade a suspended fishing line, and we also found other evidence of fishing gear along the bottom. Shortly after beginning our ascent along the wall, the canyon wall abruptly transitioned to a more mildly sloping, fine sediment environment, similar to the Northeast Channel dive site.
After a two-day delay due to weather and engine troubles, we were able to get underway yesterday afternoon, and arrived at our first dive site late this morning. Despite a later dive start, the various operational teams were able to organize quickly to allow us to stay on bottom later than usual, ensuring that we maximize our exploration time.
This first dive took place at the highly anticipated site of the Gully Marine Protected Area (MPA), which protects the largest submarine canyon in the Western North Atlantic. Specifically, we surveyed the eastern flank of the canyon. Previous studies in the Gully MPA have documented a wide diversity of habitats and species; however, many deepwater areas, particularly of this eastern flank, remained completely unexplored. The purpose of this dive was to survey the previously unexplored eastern flank of the canyon, as well as to document potentially undescribed species, particularly sponges. Furthermore, during this dive, the team sought to survey water column communities during both the descent and ascent phases of the dive in order to make connections between species living in the water column and on the seafloor