America's Deepest Coral Reef
Posted By Tim Taylor on 20 February 2007
What buoy's my emotions is thinking back on the phenomenal discovery of a new coral reef, seemingly without disease issues called Pulley Ridge. Could this be hope's reef? Is it a key to understanding the health and sustainability of the corals? Can it help us save the shallow water reefs? Pulley Ridge is a living coral reef that draws its energy from sunlight, a reef that is made up of corals common to shallow reefs all over the Caribbean. The amazing thing about this reef is that it is over 200 feet below the surface of the Gulf of Mexico in U.S. territorial waters. Scientists use the term hermatipic to describe this kind of reef. Simply put, coral shares its space with micro algae called zooxhanthellae. This algae uses photosynthesis to turn sunlight into energy and produces the by-products oxygen and carbon. The coral is able to use this waste product from the algae to build its skeletal structure and thus form vast geological formations. This process has been going on for over 40 million years. Corals are like volcanoes and tropical rainforests combined. They build land mass and capture and store the extra carbon dioxide that contributes to global climate issues. In effect, our reefs and rainforests are carbon dioxide storage units or sinks. Since our atmosphere is made up of 20.7% oxygen and 79% nitrogen, just a small amount of excess carbon dioxide can contribute to a major climatic change.
Today, Pulley Ridge is a healthy coral reef. During the last ice age some 13,000 years ago, in what was called the early Holocene marine transgression, it was dry land. When sea levels started to rise, it retained its structure and is what geologists call today a drowned barrier island. As the sea level rises, most corals grow upwards to chase the sun for the most efficient photosynthesis . At Pulley Ridge it seems the coral has adapted in new ways not yet fully understood growing thin and flat to catch the sun is one adaptation they appear to have utilized. Some scientists think there may also be alternate energy gathering systems, which the zooxhanthellae are utilizing to assist with the development of the corals at these depths. This is yet to be studied and verified. What is known is that this reef is almost 100 feet deeper than what was previously thought of as possible for corals of this kind to survive in and flourish. This chain of drowned barrier islands, now a living coral reef, has a range of almost 125 miles at depths from 200 to 300 feet. It is located on the Florida shelf in the southeastern Gulf of Mexico, about 100 miles west of Key West, Florida. Scientists attribute three factors to the existence of the amazing formation. The elevated topography and lithified substrate are a perfect base for the hard bottom coral community to take hold. The Loop Current of warm water coming north between Mexico and Cuba and almost reaching the shores of Louisiana and then back down to join the Gulf Stream supplies new recruits and warm, clean, clear water to this unique system. Finally, the site is on the edge of the Continental Shelf which drops to thousands of feet, thus creating an upwelling of nutrient-rich waters that bathe the reef.
Among some of the unusual discoveries found there is an algae called Anadyomene saldanhae, a plant which is more common in the 20 to 40-foot depth range. To find it growing at depths of 230 feet, where it receives only 5% of the sunlight that is normal at shallow depths, is a phenomenon worth studying. Far from being an isolated occurrence the large, brilliant green, meter-wide plant can be found carpeting Pulley Ridge as far the eye can see. Could it have a role in supplying oxygen to the ecosystem allowing the corals to grow? Those of us seeing its abundance first hand called it a cabbage patch reef. This, more than anything else, gives Pulley Ridge a look that is unmistakable. Dr. Sylvia Earle states "If dropped on Pulley Ridge, with one look I could distinguish it from any other place on this earth. The blue-purple coral and giant green algae make this unique on the planet."
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