A Few Words about Coral Reefs



          Coral reefs are formed by animals that belong to the same group as sea anemomes, jellyfish, and hydras. Individuals are called polyps and are usually less than 1" (2.54 cm) in diameter. A small number of species can actually measure as much as 1 foot. Each polyp has a mouth which is surrounded by tentacles. The bottom of the animal is attached to a hard surface. The polyp itself is soft -bodied and takes calcium out of the ocean water to build a limestone (calcium carbonate) exoskeleton, which is built along the lower portion of the body. As new polyps develop and grow the amount of limestone increases. When the animals eventually die, they leave the exoskeletons intact. After millions of years of polyp growth upon already existing limestone exoskeletons, huge reefs are created.

The Great Barrier Reef, Australia
Photo by R. Bruce
AHC Photographic Collection
          There are two types of corals. Hard Corals, which make tough exoskeletons in order to protect themselves, include such species as the elkhorn, brain, and star corals. The other type of corals are called Soft Corals or Gorgonians. This group includes sea whips and sea fans. these corals are more free moving because they lack rigid exoskeletons.

          In terms of biological diversity, coral reefs have been compared to the richness of the land's tropical rainforests. This ecosystem provides shelter and food for a vast number of marine inhabitants. In fact, according to Reef Relief, "Coral reefs occupy less than one quarter of one percent of the earth's marine environment, yet they are home to more than a quarter of all known species. "Coral reefs are only found in warm or tropical waters with a temperature range of only 70° - 85° F.

          Today, coral reefs are being devastated around the world in a number of different ways:
  1. Pollution of all forms affects the water quality. Oxygen and visibility are decreased while chlorophyll levels are increased. These factors result in algal blooms and diseases that afflict the coral.
  2. Overdevelopment presents several problems, such as an overall increase in pollution. Debris (like plastics) in the water threaten the survival of many marine species and actually smother the corals. Coastal development also adds silt and possibly sewage to the ocean water. Agricultural run-off is also devastating to the reefs because it contains pesticides and fertilizers.
  3. Physical Contact with the corals can be very destructive. Snorkelers or divers damage reefs by standing, actually touching, or by dragging their equipment across the corals. Boats may get grounded on the reef or tear up valuable seagrasses with their propellers. Anchors get dropped onto corals.
  4. Overfishing and Destructive Methods for Catching Fish not only physically destroy the corals, but also upsets the delicate balance between the various species that live in this ecosystem.
  5. Harvesting corals for the aquarium or souvenir market results in further destruction.

          The backbone of the coral reef are a group of fast-growing corals often referred to as Small-Polyped Stoney, or SPS corals. As already mentioned, SPS corals grow fast, 3/4" of growth in a month is not uncommon. These corals spread as they grow, covering neighbouring rocks and pieces of other coral, tying them all together to form the framework for the coral reef. When they die, their calcerous skeletons remain, providing shelter for animals, and a foothold for other corals. Until the early to mid 1980's, it was not possible to keep these corals in aquariums. New discoveries, procedures and equipment, mostly pioneered in Europe changed that. Today many types of brightly colored SPS corals are keep in aquariums around the world.

          SPS, like many other corals, reproduce in a number of ways. They reproduce sexually by releasing sperm and eggs into the water. Some corals reproduce asexually by "budding". SPS corals can also reproduce in another asexual manner. Most corals, SPS corals included, live in shallow water with moderate to heavy wave action. Occasionally, especially during storms, some branches of an SPS coral may get broken off the parent colony. The resulting fragment then gets tossed about in the surges. Eventually, it may lodge somewhere, where, if the conditions are right (notably proper lighting and water currents) the fragment will grow and create an entirely new colony. Top-level aquarists take advantage of this phenomenon when they keep SPS corals. They will "prune" a piece off an SPS colony, then attach the new fragment to another part of the tank, or a loose piece of rock with super glue. The fragment then grows in it's new spot, developing a new colony in a different part of the tank, or, in the case of a fragment glued onto a loose piece of rock, it can be sold, or preferably traded. Reef keepers (as we call ourselves) contact each other, most frequently over the internet, and swap corals (SPS and other species). This is considered preferable to buying wild-caught corals. It reduces the demand on the wild population, and a coral that has been bred in tanks for several "generations" is more hardy in an aquarium.

Acropora nasuta
Cultured in the Solomon Islands
Offered for sale by:
coralfarms.com
          This "cut and glue" technique is also being employed by companies like coralfarms.com. To the left you will see an SPS coral that they have offered for sale. This coral, like many of theirs, has been cultered in the Solomon Islands. In the past islanders earned money by diving on the reef and harvesting colonies of corals for sale. Obviously removing entire colonies depletes the population. Coralfarms.com set up a farm in the Solomons and hired local islanders to work it. They trained them not to cut the entire parent colony, but to prune fragments from it, bring the fragments back to shore, glue them to small cement discs or plugs, then return them to the lagoon where they spend the next 3 - 4 months growing. When larger, they are shipped. Meanwhile, the parent colony has also regrown.

          Although damage to reefs due to coral collection for the aquarium trade was always miniscule when compared to the effects of industry, agriculture, and urbanization, those in the trade none the less feel an obligation to improve their practices, and even give back to the environment when possible. For example, a prolonged warming spell brought about by an El Nino wiped out a soft coral from an area in Palau, Micronesia. The people running GARF.org put the word out on their web site that they wanted to repopulate Palau with the soft coral, and to that end would collect cuttings from visitors who thought they might have corals originating in that area. From all over the country people overnight shipped cuttings to GARF, which is in Idaho (believe it or not). Once there, the cuttings are DNA tested to see if they are in fact authentic Palau corals. Garf hopes to grow them out some more, and eventually reintroduce them into the wild. As an incentive, Garf has offered to swap some of their own stock in exchange for the Palau coral. Garf, is also involved with another area of interest, they collect corals for their medicinal value. Many corals are shown to contain compounds that have anti-cancer or other beneficial properties. After collecting them (by once again offering their own stock as incentive) they grow them out and donate them to research facilities, which extract the compounds from the corals and test their medicinal values.


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