Northwest Atlantic Ocean; Mid-Atlantic U.S. Canyons Exploration - EX 1404 Leg 2

During EX1404 Legs 2 and 3, our team conducted sixteen dives with ROV Deep Discoverer (D2) that explored six seamounts and nine canyons, of which four seamounts and five canyons had never been explored before. We investigated several different habitats at depths ranging from 660 meters to 4692 meters and documented deep-sea corals and their associated invertebrates, a variety of fish and other benthic animals, a diversity of mid-water fauna, and a number of species we have yet to identify.

Canyons

As was documented in 2013, the submarine canyons investigated during this expedition proved to be biodiversity hotspots, hosting many different species of coral, numerous fish species, several cephalopods (squids and octopus), and a variety of echinoderm species (e.g., sea stars, sea urchins, sea cucumbers).

These canyons were generally characterized by downslope areas of soft sediment leading up to steep walls with abundant biological communities under overhangs. Evidence of anthropogenic influence was occasional, with the exception of Ryan and McMaster Canyons where D2 encountered several instances of trash and derelict fishing gear, potentially due to its proximity to shipping channels into large cities on the U.S. East Coast.

Highlights from these dives include observations of deep sea predation, a series of caves inhabited by octopuses (dubbed octopus grottoes), dragonfish, and several areas of high coral density.

Seamounts

During our 6 dives on the New England Seamount Chain, D2 documented extensive deepsea coral and sponge habitat, patchy and often sparse fish distribution, and a variety of exciting geologic features. Seamount dives contained the highest diversity of corals of the expedition, with particularly high densities observed during our dives at Gosnold and Atlantis II. We observed several different types of lava flow, lower sediment cover with a coarser grain size compared to in the canyons, and manganese encrusting over rocks.

D2 documented potential range extensions for two species of deepsea coral, previously unknown phenomena in the water column and potential new species, and collected rare imagery of deep-sea predation and behaviors. We also conducted the deepest dive to date on the New England Seamount Chain on an unnamed and previously unexplored seamount that was first mapped in high resolution using Okeanos's EM302 multibeam system in 2013.

Highlights from these dives include D2's deepest dive to date, large colonies of precious corals, a dumbo octopus and vampire squid, several rare or unknown species, and areas of active coral recruitment.

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Revised: February 25, 2014 at 4:30 PM Central

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