Corals, including cup corals and bubblegum corals reside on the hard substrate near the edge of the mussel bed.

Corals, including cup corals and bubblegum corals, reside on the hard substrate near the edge of the mussel bed. Image courtesy of the NOAA Office of Ocean Exploration and Research, Northeast U.S. Canyons Expedition 2013. Download larger version (jpg, 1.6 MB).

Dive 13
July 21, 2013
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Highlights from Dive 13, which was conducted at “New England Seep 1,” further investigating gas seep areas previously detected in sonar data and ground-truthed during a remotely operated vehicle shakedown cruise this past June. Video courtesy of the NOAA Office of Ocean Exploration and Research, Northeast U.S. Canyons Expedition 2013. Download video (mp4, 39.4 MB).

Dive 13 was conducted at “New England Seep 1,” further investigating gas seep areas previously detected in sonar data and ground-truthed during a remotely operated vehicle (ROV) shakedown cruise this past June. From these recent dives, it was known that seeps in this area hosted chemosynthetic communities at approximately 1,400 meters deep. The ROV arrived at a soft sedimented seafloor with some small pebbles and a few coral colonies at 1,409 meters. Red crabs, rattails, cutthroat eels, urchins, black dogfish, and mesopelagic fishes were also noted. The ROV continued to the first waypoint following a sonar target to edge of a large mussel bed at a depth of 1,420 meters. This bed was mixed with live and dead mussels of various sizes (including thousands of what can be considered as relatively recent mussel recruits ~2-3 centimeters in length), with most of the dead mussels observed on the peripheries of the bed. Deep Discoverer (D2) transited several directions to get an estimate of the size of the bed (~50 meters by ~80 meters), although the mussel bed likely continued farther to the north. A line of carbonate blocks extended along the entire eastern edge of the mussel bed. Numerous variably sized white and pink bubblegum corals and cup corals were attached to these carbonates. Close-up images of the mussel assemblages revealed caprellid amphipods, scale worms, Alvinocaris shrimp, and abundant gastropods (snails). Next we searched for the multibeam sonar-detected bubble (presumably methane) plumes using D2’s camera sled and sonar. Bubbles were discovered and imaged in apparently uncolonized soft sediments at a depth of ~1,421 meters. Sediments with bacterial mats and white “marshmallow” material were observed in patches in and around the mussel bed. This mussel bed and corals were surveyed for the majority of the dive, as throughout the afternoon numerous live interactions with the Aquarium of the Pacific occurred. Imaging of white and red bubblegum corals revealed numerous ophiuroids (brittle stars) associated with the colonies. Many octopods and crabs were also observed. The ROV left bottom from a depth of 1,422 meters.