Understanding Coral Reefs
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| - | [http://blog.stevenwsmeltzer.com/what-are-coral-reefs/introduction-to-the-underwater-world/ What Are Coral Reefs] - | + | [http://blog.stevenwsmeltzer.com/what-are-coral-reefs/introduction-to-the-underwater-world/ What Are Coral Reefs] - Introduction to the Underwater World |
| - | [http://blog.stevenwsmeltzer.com/what-are-coral-reefs/ Coral reefs] | + | [http://blog.stevenwsmeltzer.com/what-are-coral-reefs/ Coral reefs] consist of tiny animals that belong to the class anthozoans, the major class of organisms within the phylum cnidaria (the "c" is silent). Cnidaria has over 6,000 identified species of jellyfish, sea pansies, sea anemones and sea fans. Corals, after their larvae phase, no longer move but are fixed in one place. This type of animal is known as a sessile animal. |
| - | + | Coral reef colonies are made of millions of these very small, cup-shaped animals termed polyps. A solitary coral polyp might be as large as a saucer or smaller than the head of a pin. Millions of polyps working together in a cooperative colony over many years create the limestone skeletons that make the framework of the magnificent coral reef. Corals begin life in tropical waters as free-floating larvae. Following a comparatively short period of time, the larva eventually attaches itself to a hard surface and becomes a polyp. [http://www.stevenwsmeltzer.com Coral reef] colonies reproduce both sexually and asexually. To reproduce, the coral polyps release both eggs and sperm into the water. (This is also called coral spawning.) One kind of asexual reproduction takes place when fragments of coral are broken off as a consequence of storm storms. The broken pieces of corals more often than not survive and continue to grow and make a new colony. This process is referred to as "fragmentation". Corals exist in colonies consisting of numerous individuals, each of which is called polyp. They secrete a hard calcium carbonate (rock-like) skeleton, which serves as a uniform foundation or substrate for the colony. This skeleton provides two essential functions, first for the coral itself it offers shelter, as the polyps can contract into the structure if predators approach and second this same skeletal structure is what creates the coral reefs over a period of time. The calcium carbonate is secreted at the bottom of the polyps, consequently the living part of the coral colony occurs at the exterior of the skeletal structure, completely covering it. The calcium carbonate created by the living colony continually adds to the dimensions of the general structure and therefore the enlargement of the coral reef. The expansion of these reef structures differs greatly, based on the varieties of coral and environmental conditions-- ranging from 0.3 to 10 centimeters per year. The skeletons of stony corals are secreted by the lower portion of the polyp. This method creates a cup, known as the calice, in which the polyp rests. The walls surrounding the cup are known as the theca, and the floor is called the basal plate. Thin, calcareous septa (sclerosepta), that give structural integrity, shelter, and an increased surface region for the polyp's soft tissues, extend upward from the basal plate and radiate inward coming from its outer wall. Periodically, a polyp will raise up off its base and secrete a new floor to its cup, forming a new basal plate above the old one. This creates a tiny chamber in the skeleton. If polyps are physically stressed or under potential attack, they contract into the calice so that almost no part is exposed above the skeletal platform. This protects the organism from predators and the elements (Barnes, R.D., 1987; Sumich, 1996). Different varieties of coral build structures of different dimensions and shapes such as brain corals, fan corals, encrusting corals, etc., making marvelous variety and complexity in the coral reef ecosystem. Various coral varieties tend to be segregated into characteristic zones on a reef, separated out by competition with other varieties along with environmental conditions. Corals contain only a narrow degree of organ development and consists of three fundamental tissue layers: an external layer or epidermis, an inner layer of cells lining the gastrovascular cavity (an internal space for digestion) and a layer called the mesoglea between the other two layers Barnes, R.D., 1987. Corals feed by reaching out with tentacles to seize prey such as small fish and planktonic animals (any drifting organisms, animal, plant, archaea or bacteria that inhabit the pelagic zone of the oceans). See Also: Creatures of the Coral Reefs Resources: Marine Species Galleries: Crustaceans and Echinoderms Moray Eels Coral Reef Images Pictures of Fish Sea Turtles Detailed Information on select Marine Species: Caribbean Fish Hawaiian Fish Sponges Crustaceans, Invertebrates, Mollusks, Echinoderms | |
