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Seafloor Characterization of the U.S. Caribbean |
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Day 5: 02/29/2008
Tourmaline Bank Complete
The crack multibeam teams worked throughout the night to accomplish significant coverage, closing out the Tourmaline Bank “proper”. Data collected to date encompasses 88 square kilometers of bank shelf and beyond. The data provides high resolution seafloor topography to connect the Tourmaline Bank conservation area and Bajo de Cico conservation area, completed in 2006.
Survey operations revealed an interesting seafloor feature located due south of Bajo de Cico. The semi-rectangular plateau was revealed for the first time in high detail resolution with distinct ledges visible on multiple sides. The depth rises up to 300 feet.
The ROV operators finished collecting groundtruth data for the shallowest portions of Tourmaline Bank. Along several ROV transects macroalgae was the predominant cover. Occasionally, patches of coral and sponges were observed. These patches generally had a high diversity of invertebrates and fishes in an area the size of a car tire. Patches with holes for fish to hide in were especially diverse.
In addition to sponges and coral patches, several sand tilefish mounds were found among vast expanses of sand and fleshy macroalgae. The mounds were composed of algal nodules (rhodoliths) and other gravel-sized hard material accumulated by the sand tilefishes. To get images of the mounds, the ROV had to hover directly above its target in sometimes screaming currents. Of course, the sand tilefish did not remain near their homes. They could be seen lurking in the periphery of view, keeping a watchful eye on the ROV.
Organisms such as coral and sponges, which required a hard substrate for attachment to the seafloor, take advantage of the sand tilefish’s work. They attach to the accumulated material. By doing this, they enhance the mound’s stability and provide habitat for other organisms.
