2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts

Dive 13: “Near Hodgsen” Seamount

Date: July 18, 2021
Location: Lat: 35.611445°, Lon: -58.206409°
Dive depth range: 2,359 - 2,531 meters (7,740 - 8,304 feet)

During Dive 13 of the 2021 North Atlantic Stepping Stones expedition, this dandelion siphonophore was seen at a depth of 2,447 meters (8,028 feet). Dandelion siphonophores are unusual and unique siphonophores because they anchor themselves to the seafloor using their tentacles. In this video, you can see the multiple threads attaching the animal to the seafloor and it appears to be potentially throwing out more threads or spawning. Video courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (mp4, 88.5 MB).

During Dive 13 of the 2021 North Atlantic Stepping Stones expedition, we explored the southern face of an unnamed seamount dubbed “Near Hodgsen” Seamount. The dive targeted a square-shaped platform at the top of the seamount that was revealed in the multibeam bathymetry data collected the night before the dive.

We started the dive at approximately 2,550 meters (8,366 feet) depth on a sedimented slope that appeared to be a chute of debris from above. During the dive, we saw several of these sediment chutes as well as large igneous boulders, lobate lava flow formations, and thick ferromanganese crust coating the rock surfaces. Biological observations were sparse throughout the dive, though we did observe several species of corals and various sponges as well as single-celled xenophyophores, sea stars, sea cucumbers, several fish, and other organisms.

During Dive 13 of the 2021 North Atlantic Stepping Stones expedition, we observed this slit limpet, a kind of sea snail in the family Fissurellidae, genus Zeidora. The slit limpet was actively eating away the surface of a rock, leaving a visible, darkly colored feeding track in its wake. As this was an unusual observation, the slit limpet was collected for further analysis.

Several large igneous boulders covered in bamboo corals were encountered midway through Dive 13 of the 2021 North Atlantic Stepping Stones expedition. Bamboo corals were locally abundant on these large boulders and more spread out throughout the dive on different hard-bottom habitats. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 596 KB).

Several of these flat-topped slabs were observed near the beginning of Dive 13 of the 2021 North Atlantic Stepping Stones expedition. They appeared to have detached from the upper summit of the seamount and fallen intact downslope along with sediments. Erosional features caused by sediments flowing downslope across the top of the slabs were visible as vertical, stripe-like patterns and fresher, blacker ferromanganese crusts could be seen precipitating on the side of these slab features.

Several of these flat-topped slabs were observed near the beginning of Dive 13 of the 2021 North Atlantic Stepping Stones expedition. They appeared to have detached from the upper summit of the seamount and fallen intact downslope along with sediments. Erosional features caused by sediments flowing downslope across the top of the slabs were visible as vertical, stripe-like patterns and fresher, blacker ferromanganese crusts could be seen precipitating on the side of these slab features. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1.5 MB).

This large pycnogonid, or sea spider, was observed feeding on a coral in the genus Hemicorallium during Dive 13 of the 2021 North Atlantic Stepping Stones expedition at a depth of 2,375 meters (7,792 feet).

This large pycnogonid, or sea spider, was observed feeding on a coral in the genus Hemicorallium during Dive 13 of the 2021 North Atlantic Stepping Stones expedition at a depth of 2,375 meters (7,792 feet). Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 874 KB).

This cute little coffinfish or sea toad in the anglerfish family Chaunacidae was seen at a depth of 2,362 meters (7,749 feet) during Dive 13 of the 2021 North Atlantic Stepping Stones expedition. This may have been a depth record for this kind of fish! Other fish seen during this dive included a large antimora and two (potentially the same) white halosaurs.

This cute little coffinfish or sea toad in the anglerfish family Chaunacidae was seen at a depth of 2,362 meters (7,749 feet) during Dive 13 of the 2021 North Atlantic Stepping Stones expedition. This may have been a depth record for this kind of fish! Other fish seen during this dive included a large antimora and two (potentially the same) white halosaurs. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1.6 MB).

Near the end of Dive 13 of the 2021 North Atlantic Stepping Stones expedition, we encountered this mature coral (Metallagorgia sp.) with a snake star deeply entwined within the center of its branches. This was the only Metallagorgia coral seen on the dive, though we did observe several primnoid octocorals, Bathypathes black corals, and Chrysogorgia soft corals.

Near the end of Dive 13 of the 2021 North Atlantic Stepping Stones expedition, we encountered this mature coral (Metallagorgia sp.) with a snake star deeply entwined within the center of its branches. This was the only Metallagorgia coral seen on the dive, though we did observe several primnoid octocorals, Bathypathes black corals, and Chrysogorgia soft corals. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1 MB).


Location of Dive 13 of the 2021 North Atlantic Stepping Stones expedition on July 18, 2021.

Location of Dive 13 of the 2021 North Atlantic Stepping Stones expedition on July 18, 2021. Map courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 3 MB).

Image showing the dive track of Dive 13 of the 2021 North Atlantic Stepping Stones expedition. Scale is water depth in meters.

Image showing the dive track of Dive 13 of the 2021 North Atlantic Stepping Stones expedition. Scale is water depth in meters. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1.8 MB).