Dive 20: Middle Bank
September 26, 2017
Access Dive Summary and ROV Data
Loading the player...

Dive 20: All That Glitters

Precious gold coral was seen colonizing bamboo coral while exploring Middle Bank, just outside Papahānaumokuākea Marine National Monument. During initial colonization, the gold coral rapidly consumes its host; however, overall, these corals grow very slowly and the large sizes of the colonies seen suggest that some of the colonies could be nearly 2,000 years old. Video courtesy of the NOAA Office of Ocean Exploration and Research, Deep-Sea Symphony: Exploring the Musicians Seamounts. Download (mp4, 37.1 MB)

During Dive 20, the team investigated a conical feature primarily of volcanic origin located on the top of Middle Bank’s carbonate platform that may be the result of secondary volcanism. Our objective for today's dive was to explore for precious coral and bottomfish habitats. Remotely operated vehicle Deep Discoverer (D2) arrived on bottom in 475 meters (1,558 feet) depth near the base of the cone on a featureless flat seafloor. Two Dogfish sharks, corals (primnoid and victorgorgia), an urchin, and a purple scleractinian coral with an associated squat lobster were observed in close proximity. D2 imaged “dissolution holes” in the pavement surface, suggesting it was composed of carbonate. A Corallium precious coral, the first documented on Middle Bank, was observed not far from an Asterphiura false sea star. The slope increased, remaining generally consistent until D2 reached closer to the summit. Some carbonate ledge “tongues” with dark material and thin veins of tan were observed, one with many corals on the tip. Upslope, we encountered a band of gold corals in high density. Several colonies were quite large and likely several hundreds of years old, if not older. The dive concluded on an extensive high-density community of small black corals that continued upslope. This dive was particularly exciting for our fish biologist team. We encountered a diversity of fish, including a chaunax, a large school of amberjacks, an aggregation of nine conger eels, and an unusual sighting of a Bandfish was imaged at about 355 meters (1,164 feet) along with a potentially new fish, orange with big black eyes, that stumped our science team.