FAQ'S

What is a coral reef?

Coral reefs are wave-resistant structures resulting from cementation processes and the skeletal construction of hermatypic corals, calcareous algae, and other calcium carbonate-secreting organisms. They are the “Rainforests of the Sea.” Coral Reefs also support 25% of all marine life while making up less than 1% of the ocean floor. They are with out question the most diverse eco-system on the planet.

Where can coral and coral reefs be found?

Corals can be found throughout the world’s oceans, but reef-building corals are limited to oligotrophic (low nutrient) subtropical and tropical seas. Temperature and light are the primary factors which limit the growth of coral reefs. Coral reefs are restricted to a seawater temperature range of 65F to 97F and optimal reef growth occurs between 79F-82F. Light intensity decreases exponentially with depth in seawater, and, likewise, so does coral symbiont photosynthesis and coral calcification. Coral reefs are thus limited to depths of less than 20 meters assuming water clarity is satisfactory. At depths greater than 20 meters light intensity is not sufficient to promote necessary growth rates for reef development. Salinity, wave energy, water column nutrient levels, and sedimentation are also important factors which limit reef development. Optimal coral calcification occurs at normal oceanic salinities of 33-36 parts per thousand, in low nutrient level water, and in areas where sedimentation is low. Coral reefs do best in areas with moderate and continuous wave activity that is necessary to wash vital nutrients across the reef and remove unnecessary waste products. The crucial role of all these factors can be seen surrounding large river deltas in the tropics, such as the Amazon and Orinoco River. Latitudinal position is conducive to reef development, but du to the vast amounts of highly turbid, freshwater that exit these watersheds hinder any reef development. Coral reefs do not develop because of low salinity, as well as the high levels of nutrient and sediment inputs from land, which work to decrease the necessary light intensity required for reef-building corals to grow and calcify. The pollution that is contained in this run off is devastating to coral reef ecosystems.

How fast do coral reefs grow?

Coral reefs grow at a rate of roughly 4 meters every 1000 years. Under pristine conditions with little physical disturbance it is possible for reefs to grow at a rate of roughly 20 meters every 1000 years. These pristine areas are no longer.

How much are coral reefs actually worth?

In the Florida Keys alone, it has been estimated that coral reefs contribute $1.2 billion annually to the economy as a result of eco tourism; specifically, recreational diving, sport fishing, commercial fishing etc. In sum, coral reefs "are the foundation for a $4.3 billion tourism economy that provides over 23,600 jobs." (EMS web page) Globally it is estimated that coral reefs are worth somewhere in the neighborhood of $375 billion annually. From Stuart to South Miami they support in Scuba alone $3.6 billion in annual revenues. It is near impossible to put a dollar amount on the revenue created from the fisheries they support. 

How important are coral reefs to commercial and sport fishing?

While coral reefs are home to more than one quarter of all the known marine fish species they make up less than 1% of the ocean floor. When reefs are properly managed it is estimated that they can produce 15 metric tons of fish and other seafood per square kilometer per year!! From this data, one can immediately inductively draw conclusions as to the importance of reefs in sport fishing. Many marine game fish species, such as tarpon, grouper, snook, barracuda, dolphin to name a few utilize reef habitats for at least part of their life cycles. Thus, the survival of recreational and commercial fishing is extremely dependent upon the health of coral reefs.

Why are the healthy reefs so important to the survival of marine species?

Reefs provide marine life with breeding areas and shelter from predators, this allows for increased development of the food chain. The vegetation which thrives on reef structures, provide marine life with the nourishment they need to survive. The exchange of fish DNA between existing reefs will increase their abundance, strength and health.

What are the effects of coral bleaching?

Mass bleaching of corals is now the biggest threat to the survival of coral reef ecosystems. Coral polyps harbor symbiotic algae called zooxanthellae, which provide the necessary nutrients for reef building corals to calcify reef structures. When a coral bleaches it loses its symbiotic zooxanthellae and will die within a short period of time unless it regains it. Many hypotheses exist as to the cause behind coral bleaching, but the strongest evidence points to elevated sea surface temperatures as being the main catalyst. It is hypothesized that stress induced from pollution, ultraviolet radiation, and changing salinity also play a role in the extent of coral bleaching. With the current sea surface temperature warming trend, likely due to global climate change, along with the apparent increase in frequency and intensity of El Nino events, coral reefs, as we know them, are at an extreme risk of becoming extinct within the next 50 years.

What plants and animals are found on and near coral reefs?

Coral reefs are home to more than one quarter of all the known marine fish species. The complex topography of reefs also provides exceptional habitat for a plethora of other marine organisms, such as lobsters, crabs, shrimps, mollusks, clams, starfishes, worms, sea urchins, algae, anemones, fishes, sharks, sponges, and thousands of microscopic bacteria, animals, and plants.

Why are there so many other plants and animals on coral reefs?

The brilliant and beautiful topography of reefs provides superior refuge for hundreds of thousands of species, which utilize reef habitat for protection, living substrate, and food. Every nook, cranny, cavern, and overhang on a healthy coral reef is overflowing with different life forms and this immense biodiversity has earned coral reefs the nickname of "the rainforests of the sea." Aside from their awe-inspiring vertical relief, coral reefs are an oasis of nutrients and food in tropical waters. The high productivity of coral reefs is due to the primary production of millions of tiny photosynthetic organisms, which utilize energy from the sun to build necessary organic matter. This organic matter is the starting point of the complex, yet efficient, food web of coral reefs, which support the unique variety of species from tiny mollusks to large sharks.

Why are there so many different kinds of fish?

Due to their immense species diversity and spectacular geologic framework, coral reefs provide ideal habitat for thousands of fish species. Through time many different fishes have evolved with reefs to take full advantage of all the biological productivity. The diversity of habitats and food sources is responsible for the vast amount of fish species. Different fishes may feed on algae, living coral tissue, plankton, other fishes, and some small "cleaner fishes" actually feed on the parasites of larger fishes. Reef fish dynamics are very complex as some fish may only live on the reef as juveniles and then migrate to different habitats once they mature. On the flip side, many juvenile fish species utilize neighboring mangrove and sea grass habitats for refuge and migrate to the reef later on in their life cycles. Other fishes may take up residence in neighboring marine communities and only visit the reef occasionally. Thus, at any given time there is a large number of fish species present in coral reef communities. This almost unimaginable balance between so many different types of fishes with variable life cycles is one of the attributes of coral reefs which make them unique on this planet.

Why are reef fish so easily caught?

Many fish that inhabit reefs are inquisitive, which make them easy targets for cyanide and spear fishermen. For example, large groupers, which are now a rare sight on many reefs due to their commercial value, tend to be very territorial and hold there ground when approached making them sitting ducks for spear fisherman. Other fish can be easily sprayed with cyanide, which many times results in the stunned fish seeking shelter and the diver hacking away at old coral growth to reach the hidden, incapacitated fish. The growing demand for reef fishes, both for consumption and the aquaria trade, has increased the amount of fishermen using these tactics, which can quickly cause local fish populations to be harvested to near extinction.

What ecological roles do they play on coral reefs?

Reef fishes contribute a large amount of biomass to reef ecosystems. Herbivorous fishes help control algal populations and keep fast growing algal species from out competing slow growing corals. It is estimated that herbivorous fishes ingest over 60% of the standing crop of algae present on reefs. Reef fishes are vital in that they transport large quantities of inorganic and organic nutrients between different sites of the reef as well as between off-reef and reef locations. For example, the common grunt will migrate to and from neighboring sea-grass beds to feed. Thus, their fecal matter and urine greatly enrich reef communities with nitrogen, phosphorus, and particulate organic carbon. Also, it has been found that minerals captured by planktivorous damselfishes are deposited by the fish in their nocturnal shelters. In sum, the ecology of reef fish is an area that has been poorly investigated, yet, reef fish are known to be important to the biochemical cycling on reefs.

What happens to the reef when the top predators disappear?

The top predators on coral reefs, such as sharks and barracuda, help to control the number of omnivorous and herbivorous organisms. If sharks and barracuda were to disappear from reef ecosystems, herbivore populations would increase. At first, one would think that this would be a good occurrence for a coral reef given the importance of grazing in the control of algal populations. Unfortunately, this presupposition is false. First, large predatory and herbivorous fish have been severely over-harvested for centuries. This, in turn, explains the high densities of the long spined sea urchin, Diadema antillarum, on Caribbean reefs prior to the early eighties. In the absence of predators and competing herbivores, D. antillarum became keystone specie in the control of macroalgae abundance. In late 1982 an unknown pathogen killed well over 90% of D. antillarum in the Western Atlantic. An explanation that has been put forth for the ecological extinction of this keystone specie is that due to severe over fishing, populations of D. antillarum were no longer held in check. Consequently, their numbers became very dense; making them extremely susceptible to disease as a result of the enormously increased rates of transmission. Likewise, it is believed that the mass removal of grazers and predators leave marine ecosystems vulnerable to invasion from disease. Macroalgae overgrowth of corals has been identified as one of the factors responsible for the demise of coral reefs in the Caribbean since the ecological extinction of D. antillarum. From this one example, we can see the inherent, unknown, and fragile complexities that exist in coral reef ecosystems, thus, making their future existence extremely susceptible to disturbance events.

-Jackson, J. B. C., Kirby, M. X., Berger, H., Bjorndal, K. A., Botsford, L. W., Bourque, B. J., Bradbury, R. H., Cooke, R., Erlandson, J., Estes, J. A., Hughes, T. P., Kidwell, S., Lange, C. B., Lenihan, H. S., Pandolfi, J. M., Peterson, C. H., Steneck, R. S., Tegner, M. J., and R. R. Warner. 2001. Historical Overfishing and the Recent Collapse of Coastal Ecosystems. Science, 293: 629-636.

What happens to the reef when the herbivores (fish, sea urchins) disappear?

Herbivores are a vital component to the ecological balance of coral reefs. Fishes and sea urchins are responsible for limiting the density and spatial organization of plant communities on reefs. Grazing of algae, which is competitively superior to coral, is the primary role of herbivores on reefs. Optimal grazing is a fundamental requirement for coral larvae to settle, mature, and calcify reef structures. Thus, if reef herbivores suffer population declines, slow growing coral will be quickly smothered and overgrown by algae, which would result in substantial coral mortality. A well-documented example of the importance of reef grazing was the almost complete elimination of the long-spined sea urchin, Diadema antillarum, in the Caribbean. Following the population crash of D. antillarum many historically prominent coral reefs in the Caribbean became overgrown and dominated by macroalgae providing a deleterious, yet picture perfect example of the delicate balance of reef ecosystems.

-Glynn, P.W. 1990. "Feeding Ecology of Selected Coral-Reef Macroconsumers: Patterns and Effects on Coral Community Structure." Ecosystems of the World v. 25-Coral Reefs. Edited by Z. Dubinsky. Elsevier Science. New York, NY.

What are coral reef diseases?

Reef building corals appear to have become more susceptible to disease following the numerous stressors imposed on them by human activity. In the mid 1970’s the first reports surfaced in regards to corals being stricken with disease. The first disease identified was named Black-band disease because the disease itself appears as a black line a few millimeters wide across the surface of a coral colony. Black-band disease is caused by microorganisms, which produce anoxic conditions and hydrogen sulfide deep within the band that kills the underlying coral tissue. The disease causing microorganisms then utilize the organic material from the killed coral tissue to grow and proliferate. The visible "black-band" moves across living coral tissue at a rate of a few millimeters per day leaving dead coral skeleton behind. Different coral species seem to have varying susceptibility to Black-band disease. Massive brain and star corals are the most affected by Black-band, whereas, Elkhorn, Staghorn, and pillar corals resist infection. Healthy corals can become infected with Black-band disease by coming in contact with an infected colony, but damaged corals are at the greatest risk of being stricken with the disease. At roughly the same time Black-band disease was first reported, both Elkhorn and Staghorn coral colonies in the Caribbean began to exhibit what is now commonly referred to as white-band disease. White-band disease starts killing coral tissue at the base of the coral colony and moves up towards the tips at about the same rate as black-band disease. The cause of white-band disease is still unknown. White-band disease is responsible for completely obliterating the once beautiful and common stands of Elkhorn coral in the Florida Reef tract. To see a colony of Elkhorn coral in the Florida Keys is now a rare occurrence.

-Peters, E. C. 1997. "Diseases of Coral Reef Organisms." Life and Death of Coral Reefs, Ch. 6. Edited by Charles Birkeland. Kluwer Academic Publishers. Boston, MS.

Where can I find out about coral reef diseases?

What can I do to help?

Join to fight to “SAVE THE REEFS.” Sponsor a Living Circle today. With your help, we can make an immense impact on our oceans health. “Living Circles” are a unique way that we can all leave an individual legacy. With each sponsorship you make, your name or company’s name will be placed underwater on a bronze plaque at the project site.You may even choose to dedicate your “Living Circle” or circles to a friend, loved one or deployed solider. As an individual or a company, you can choose to sponsor as many Living Circles as you wish, knowing that with each placement, you are helping to secure for future generations the same luxuries we enjoy today. This is an opportunity to take an active role in the preservation of our oceans. Please, set the example and help send a message to the thousands of others who are concerned about and committed to the preservation of our environment. Your grandchildren will thank you and our oceans look forward to hearing from you.