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

Dive 19: Retriever Seamount

Date: July 27, 2021
Location: Lat: 39.838919°, Lon: -66.228647°
Dive depth range: 1,822 - 1,936 meters (5,978 - 6,352 feet)

High-diversity coral environments were found throughout Dive 19 of the 2021 North Atlantic Stepping Stones expedition, particularly on areas with displaced ferromanganese-encrusted boulders and lobate and pillow lava outcrops.

High-diversity coral environments were found throughout Dive 19 of the 2021 North Atlantic Stepping Stones expedition, particularly on areas with displaced ferromanganese-encrusted boulders and lobate and pillow lava outcrops. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1.3 MB).

Dive 19 of the 2021 North Atlantic Stepping Stones expedition took place on one of the prominent pinnacles of Retriever Seamount, which is one of four seamounts within the Northeast Canyons and Seamounts Marine National Monument. It is the shallowest dive to date on Retriever Seamount and marked the last dive of the expedition during which we explored a seamount or reached the seafloor.

Although the dive was restricted to a single pinnacle on the seamount’s summit, a wide variety of seafloor types were encountered, including loose ferromanganese-encrusted and displaced cobbles and boulders, gravel-mantled sediment plains, and lobate and pillow lava outcrops. It appeared that the bottom type had a significant influence on the distribution of organisms on the seafloor. Biologically, this was a dense, high-biomass, high-diversity coral garden site, broken only by small plateaus of sediment in places. Overall, 29 species of coral were observed directly during the dive, as well as numerous species of sponges, brittle stars, crinoids, anemones, hydroids, bryozoans, and several species of fish.

This spiral Iridigorgia coral, seen during Dive 19 of the 2021 North Atlantic Stepping Stones expedition, was covered in crinoids, an unusual observation. Throughout the dive, we observed 29 different species of coral, including corals belonging to the genera Metallogorgia, Paramuricea, Acanella, Paramuricea, Hemicorallium, Acanthogorgia, Clavularia, Anthomastus, Iridigorgia, Paragorgia, Isidella, Swiftia, Candidella, and Chrysogorgia.

This spiral Iridigorgia coral, seen during Dive 19 of the 2021 North Atlantic Stepping Stones expedition, was covered in crinoids, an unusual observation. Throughout the dive, we observed 29 different species of coral, including corals belonging to the genera Metallogorgia, Paramuricea, Acanella, Paramuricea, Hemicorallium, Acanthogorgia, Clavularia, Anthomastus, Iridigorgia, Paragorgia, Isidella, Swiftia, Candidella, and Chrysogorgia. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1.1 MB).

Towards the end of Dive 19 of the 2021 North Atlantic Stepping Stones expedition, we continued to observe the scattered rock debris sitting on the lobate and pillow lava outcrops that we’d seen earlier, suggesting that the pinnacle of Retriever Seamount was perhaps a late-stage eruption site and that it remains largely susceptible to continued erosional modification.

Towards the end of Dive 19 of the 2021 North Atlantic Stepping Stones expedition, we continued to observe the scattered rock debris sitting on the lobate and pillow lava outcrops that we’d seen earlier, suggesting that the pinnacle of Retriever Seamount was perhaps a late-stage eruption site and that it remains largely susceptible to continued erosional modification. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 413 KB).

This large bubblegum coral (Paragorgia arborea) was observed during Dive 19 of the 2021 North Atlantic Stepping Stones expedition. Based on published radial growth rates for this species, this colony is approximately 100 years old! We saw several large coral colonies during the dive, prompting one of our on-shore scientists to refer to the dive site as “the land of giants.”

This large bubblegum coral (Paragorgia arborea) was observed during Dive 19 of the 2021 North Atlantic Stepping Stones expedition. Based on published radial growth rates for this species, this colony is approximately 100 years old! We saw several large coral colonies during the dive, prompting one of our on-shore scientists to refer to the dive site as “the land of giants.” Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 1.2 MB).

Seen at a depth of 1934 meters (6,345 feet), this gadiform fish in the genus Lepidion was one of several species of fish observed during Dive 19 of the 2021 North Atlantic Stepping Stones expedition.

Seen at a depth of 1934 meters (6,345 feet), this gadiform fish in the genus Lepidion was one of several species of fish observed during Dive 19 of the 2021 North Atlantic Stepping Stones expedition. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 849 KB).

This sea urchin in the genus Echinus was observed during Dive 19 of the 2021 North Atlantic Stepping Stones to have seemingly eaten over half of a bamboo whip coral.

This sea urchin in the genus Echinus was observed during Dive 19 of the 2021 North Atlantic Stepping Stones to have seemingly eaten over half of a bamboo whip coral. Image courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 744 KB).


Location of Dive 19 of the 2021 North Atlantic Stepping Stones expedition on July 27, 2021.

Location of Dive 19 of the 2021 North Atlantic Stepping Stones expedition on July 27, 2021. Map courtesy of NOAA Ocean Exploration, 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts. Download largest version (jpg, 2.5 MB).

Image showing the dive track of Dive 19 of the 2021 North Atlantic Stepping Stones expedition. Scale is water depth in meters.

Image showing the dive track of Dive 19 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, 1.4 MB).