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Seafloor Characterization of the U.S. Caribbean |
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Day 7: 03/27/2006:
Several kilometers offshore of Buck Island the shelf edge gives way to a slope that drops precipitously from 100 m to 1000 m in little over 2 kilometers. The majority of the shelf slope runs parallel to Buck Island’s shoreline, but there is an anomalous elevated spur connected to the slope that extends northward toward the eastern edge of the Buck Island National Monument. The two surveys performed today were chosen to characterize this spur. One transect ran along the eastern slope of the spur at the 800 m bathymetric contour and a second transect ran up the spur from the 800 m contour to the spur’s apex at 600 m.
Most of the habitat was steep and covered in sediment with occasional rock outcroppings. At several of the rock outcroppings coral and sponges were attached, but it could not be determined why they grew at some outcroppings and not at others. Whenever coral was present sharks, fish, isopods, sea cucumbers, crabs, jellyfish and salps were observed in the area. In between outcroppings, a covering of grayish sediment predominated, but it was not devoid of life. Haphazardly etched tracks, holes and mounds were abundant.
Several organisms worth special mention were a fish (taxa unknown) with elongated pelvic fins, a cluster of coral whips which resembled tulips and a white lobster. The fish’s fins were almost as long as its length and were splayed out forward to form a tripod with its caudal fin. The fish rested motionless on its tripod at a 45 degree angle. The tripod provided clearance from the soft sediments underneath. Perhaps it was waiting in the semi-erect position for unwary prey. The coral whips eerily emerged from the sediment, clustered in a 20 sq. m plot as if deliberately planted. Each coral resembled a tulip, because of a gelatinous “bloom” in the shape of a tulip bloom at its end. The ROV observed white crabs on several blooms. Could they be eating plankton and particles which were caught? A white lobster as seen in a previous dive was spotted. It retreated into a hole in the sediment, allowing the ROV team a glimpse of at least one of the types of animals which inhabited the ubiquitous holes. The ROV team had considerable diving and surveying experience in shallow waters, but they had never seen any of the species seen at these depths before.
![[A fish rests on a tripod formed by elongated pelvic and casual fins. The tripod increased the distance between the fish and sediment and gave the fish a 45 degree angle posture. The image was taken at 800 m below surface NE of Buck Island.]](../images/Day7_Image1.jpg)
A fish rests on a tripod formed by elongated pelvic and casual fins. The tripod increased the distance between the fish and sediment and gave the fish a 45 degree angle posture. The image was taken at 800 m below surface NE of Buck Island.
![[A coral whip with a white crab clinging to what may be a gelatinous bloom at the whip’s apex. A small shark with large eyes swims away from the ROV in the background. The image was taken at about 700 m below surface NE of Buck Island.]](../images/Day7_Image2.jpg)
A coral whip with a white crab clinging to what may be a gelatinous bloom at the whip’s apex. A small shark with large eyes swims away from the ROV in the background. The image was taken at about 700 m below surface NE of Buck Island.