For many people, the images they have seen of corals and coral reefs are of two extremes. At one end of the spectrum are the more commonly seen "shallow reefs" - colorful explosions of various shapes and sizes, mostly fueled by the combination of specialized algae (zooanthellae) that reside within the coral itself, and photosynthesis, the process by which plants use sunlight to convert carbon dioxide into organic compounds. Stereotypical iconic images of tropical reefs - from Hawaii to the South Pacific to the Caribbean to Australia's Great Barrier Reef - are compliments of the ocean's shallow coral reef ecosystems.
At the other end are the deep water corals, where light is scarce and so a different type of ecosystem flourishes. Without the supporting zooanthellae algae, deep water corals often consist of large stony corals and will aggregate in thickets or groves, forming very different reef structures compared to their shallow water cousins. Much of what we know about deep water corals, we have learned from manned deep submersibles or unmanned ROVs.
However, as we find in so many other aspects of life, nature has its middle ground. In this case, mesophotic coral reefs. These are coral ecosystems that basically exist between 30-40m (100-130 feet) down to around 150m (490 feet), which puts you at the edge of darkness. Existing beyond the range of typical scuba diving limits, mesophotic coral ecosystems have largely existed underneath the scientific radar. There's much we still need to learn about these coral reefs and the biodiversity that they support.
So when new mesophotic coral reefs are discovered, it's newsworthy indeed. Last week, NOAA announced the discovery of a large mesophotic coral reef off the southwestern coast of Puerto Rico. Found by Dr. Richard Appledoorn and his staff from the University of Puerto Rico, the reef is basically a 12-mile span, supporting a variety of plate-type corals, like lettuce and star corals, and various sponges along with groupers, snappers and reef sharks.
NOAA, along with Appledoorn, are vowing to protect this new find and managers with Puerto Rico's Coastal Zone Management are giving it serious consideration.
"We recognize the need to extend protections to mesophotic coral ecosystems in Puerto Rico, and the information being provided by this research is key to making that happen," said Ernesto Diaz, director of Puerto Rico's Coastal Zone Management Program.
The newly found reef could also benefit from fortuitous timing. Representatives from Puerto Rico and the Virgin Islands are meeting to consider a joint program of coastal management and conservation. Under discussion is a coastal zoning map that would consider the best and most ecologically sustainable uses of the coast for recreational and commercial activities - from tourism, aquafarming, to ocean energy development. Coral reef protection, of all types, would be a key component of the program.
While shallow coral reefs might provide the laymen with the most colorful images to use for making the case for coral conservation, scientists realize that, from the surface to the deepest depths, each of the various strata that make up the entire coral reef ecosystem play an important role in maintaining a healthy and vibrant marine biodiversity. All must be protected, whether we see them or not.
Read about Puerto Rico's mesophotic coral reefs in redOrbit.
Read about mesophotic coral reef systems at www.mesophotic.org.
Photo credit: H. Ruiz/NOAA