Today’s dive was along the north wall of Keller Canyon, about 26 miles from Cape Hatteras, North Carolina. This area was first mapped with high-resolution multibeam sonars by partners at the U.S. Geological Survey. The dive started with an abundance of marine snow and suspended sediment, which limited the visibility of the remotely operated vehicles (ROVs). A similar high biomass and sedimented layer in the water column has been observed in other canyons, often referred to as a nepheloid layer, but one had not previously been observed in the Keller Canyon. The ROVs passing through this layer were ROV Seirios (primarily a camera and light platform) connected to NOAA Ship Okeanos Explorer and ROV Deep Discoverer (D2) connected to Seirios via a 30-meter (98 feet) tether. Seirios means brightest star in the sky and this camera sled is used to light the way and keep an “eye” on D2. This layer in the water column prevented Seirios from being able to see and track D2, so the vehicles were brought up to approximately 540 meters (about 1,772 feet) until visual contact between the two vehicles could be reestablished. The large amount of biomass in the water column led the scientists to hypothesize that they would find many species on the seafloor and they were not disappointed.
Once visual contact was acquired, ROV Deep Discoverer was on the seafloor from 15:03:46 - 20:21:48 UTC, starting at a depth of 578 meters (1,896 feet). D2 ascended a very steep slope (up to 38 degrees) along a ridge at the top of the canyon wall. Throughout the dive, the ROV imaged eelpouts, pyciniconids (sea spiders) including some males carrying eggs, squids including short-finned squid, sea stars, octopuses (for a Happy Octopus Friday!), brittle star arms sticking out of the seafloor, gastropods, spoon worms, hydrozoans (hydroids), octocorals some having amphipod commensals, an armored sea robin, jellies, blackbelly rosefish, snipe eel, rat tails, an unidentified larval fish, combo of hydroids and stalked forams, squat lobsters (including a chirostyloid not seen previously), and ribbon worms. The scientists collected one of the ribbon worms along with a sediment sample for further identification back in the laboratory onboard NOAA Ship Okeanos Explorer. Narmidian worms, or ribbon worms, can grow up to several meters long, but the one collected today was much smaller. The scientists also observed an unidentified fish, either a toadfish or a wrymouth, which would be a new depth limit for the species. Towards the end of the seafloor portion of the dive today, the scientists observed bacterial mats on the seafloor which are usually seen around seeps in this area. Prior to leaving the seafloor, an additional rock and sediment sample with biological organisms were collected (visit the dive summary for a closer look at the samples collected). The dive ended at a depth of about 506 meters (about 1,660 feet), and the team moved into position for midwater transects.
The high productivity in the water column led to a very interesting start to the water column survey, with a great density of organisms at the 500-meter depth. Decreasing numbers of organisms were found at the 400- and 300-meter depth transects. Some of the species seen throughout the water column transects included lobed ctenophores, siphonophores, jellies including comb jellies, amphipods, shrimps, copepods,and chaetognaths (arrow worms). During the water column transects, D2 collected water samples in the midwater. Learn more about why scientists collect this water and what they can learn from it here.
Stay tuned for tomorrow as NOAA Ship Okeanos Explorer investigates gaseous seep communities at the “Pea Island” dive site.