Cold-Water Corals – the Hidden Ecosystem in the Seaways of the Bahamas

Presented by Gregor Eberli

Gregor Eberli, Thiago B.S. Correa, Mark Grasmueck, Kimberly Galvez, John K. Reed, and Dierk Hebbeln

The deep seaways surrounding the Bahamas contain a thriving ecosystem of cold-water coral reefs. These corals live in several hundred meters of water depth in cold and dark waters. Like their shallow-water counterparts, these corals form diverse ecosystems that are highly adaptable to varying environmental conditions and develop a wide variety of mound morphologies. The largest cold-water coral province of the region exists in the Straits of Florida where cold-water corals far outnumber the shallow-water corals on the Florida shelf. Several research cruises, using multibeam bathymetry echosounders, remote operated underwater vehicles equipped with cameras, and submersible dives have documented the unexpected abundance and variability of cold-water communities in the Bahamas. They form coral mounds that can be as high as 200 meters and several hundreds of meters wide. The mound morphology is primarily controlled by ocean currents and the topography created by sedimentation processes along the slope. While currents are rather uniform in strength coral mound coverage and height varies widely. At the toe-of-slope of Great Bahama Bank large mounds (120m) follow low-relief ridges that trend perpendicular to the platform, while in the middle of the Straits mound coverage is high (70%) but mound height is small (5-10m. In all locations, however, the mounds a teeming with live, harboring a diverse fauna that include 21 species of cold-water corals, a variety of sponges, several species of stalked crinoids and sea urchins. Several of the sponges have been harvested for medical research as they contain compounds that can be synthesized to produce medication for cancer treatment. The coral mounds are also the habitat for a large number of deep-water fish. The cold-water corals also offer the unique opportunity to study the effects of climate change, ocean acidification, and global warming on the deep waters of the oceans.