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Coral Reefs Marine Science What are Coral Reefs? Coral Reefs are the "Rainforests" of the ocean. Reefs are ecologically important ecosystems and have a high biodiversity that serves as a storage bank of rich genetic resources. They are a source of food and medicine, and they protect the coast from wave erosion. Coral Reefs The Organisms That Build Reefs Coral reefs are made of vast amounts of calcium carbonate (CaCO3), limestone, that is deposited by living things Corals: Structure and Variety Reef Corals Corals are cnidarians, unlike many other cnidarians, they lack a medusa stage and live only as polyps In reef-building corals the polyps produce calcium carbonate skeletons, billions of these tiny skeletons build a massive reef Not all corals build reefs The Coral Polyp Coral polyps are not only small, but deceptively simple in appearance, they look much like little sea anemones. They have an upright cylinder of tissue with a ring of tentacles on top, they use these stinging tentacles to catch food, especially zooplankton, the tentacles surround the mouth The Coral Polyp A single founder polyp lands somewhere on the ocean floor and if it survives, it divides over and over to form the colony, thus all polyps in a coral colony are genetically identical copies of the founder polyp The digestive and nervous systems of the polyps remain connected The Coral Polyp Nearly all reef-building polyps contain symbiotic zooxanthellae- a dinoflagellate algae These zooxanthellae provide coral with the energy they need to build their CaCO3 skeleton, without these zooxanthellae there would be no coral reefs Coral Nutrition Zooxanthellae perform photosynthesis and pass some of the organic matter they make onto the coral Coral polyps are very efficient at removing zooplankton brought in by currents therefore the reefs have been called a “wall of mouths” Conditions for Reef Growth Reefs are rare on soft bottoms because coral larvae need to settle on a hard surface Coral Reef Spawning Light and Temperature Corals can only grow in shallow water, where light can penetrate, because the zooxanthellae need the light Coral reefs are therefore found only on continental shelves, around islands or on top of seamounts Corals also prefer clear waters, so that light can get through, and corals can only reproduce is the average water temperature is above 68 F Where coral reefs are found Light and Temperature If water to too warm, corals will expel their zooxanthellae, this is called coral bleaching because the corals turn white without their symbiotic zooxanthellae Widespread coral bleaching occurs when El Nino occurs, because it brings warm water to many parts of the ocean Global Warming Sediments, Salinity, and Pollution Fine sediment, like silt, is very harmful to corals, it clouds the water To remove sediment, corals slough off mucus, which carries the sediment off with it Coral Diseases Fringing Reefs These are the most common and simplest kind of reef Rocky shorelines provide the best conditions for fringing reefs, these reefs grow in a narrow band or fringe along the shore The longest reef in the world is a fringing reef that runs 4000 km (2,500 mi) along the coast of the Red Sea, the climate is dry and no streams bring in sediment or freshwater Types of Reefs Barrier Reefs Barrier reefs also lie along the coast, but occur considerably farther from shore, occasionally as far as 100 km (60 mi) or more Barrier reefs are separated from the shore by a relatively deep lagoon Barrier Reefs The largest and most famous barrier reef is the Great Barrier Reef, it runs more than 2,000 km (1,200 mi) along the northeastern coast of Australia, it varies in width between15 and 350 km (10 and 200 mi) The Great Barrier Reef is actually a system of more than 2,500 smaller reefs and lagoons Atoll Structure An atoll is a ring of reef, they can be found far from land, rising up from depths of thousands of meters or more Atolls may be anywhere from one mile across to well over 20 miles Atolls may include a dozen or more islands and be home to thousands of people Atoll are rings of reef, with steep outer slopes, that enclose a shallow lagoon How Atolls Grow An atoll begins as a fringing reef around a volcanic island, as the island slowly sinks, the reef flat gets wider and deeper and eventually becomes a lagoon, at this stage the fringing reef has become a barrier reef, eventually the island sinks altogether, leaving only a ring of living growing reef, an atoll The Ecology of Coral Reefs Coral reefs are the richest and most complex of all marine ecosystems, thousands of species may live on a reef Coral Diversity Medicine from the Sea Warm up What are the three types of Reefs? What are some limiting factors for the growth and reproduction of coral reefs? Describe a coral polyp. Why are Zooxanthellae important to corals? The Trophic Structure of Coral Reefs Using sunlight, zooxanthellae incorporate nutrients into organic compounds, which are passed on to the coral The waste products of fish can be an important source of nutrients and help the coral grow faster Seaweeds are an important primary producer on the reef, and many fishes, sea urchins, snails, and other animals graze on these seaweeds Competition Corals compete for the space they need in many ways, fast-growing ones tend to grow upward and then branch out, cutting their neighbors off from light Other corals actually attack their neighbors by digesting the tissues of the other corals or by stinging them Predation on Corals A variety of animals eat the corals, they keep the reef in tact by just eating individual polyps or bits and pieces of the reef Ex. Parrotfish, Angelfish The Crown-of-Thorn Sea Star The crown-of-thorns feeds by pushing its stomach out through the mouth and digesting the coral tissue with the stomach Coral harbors symbiotic crabs, shrimps, and other fishes that discourage the sea star predation by pinching and biting their tube feet The Crown-of-Thorn Sea Star The crown-of-thorns sea star has undergone population explosions on many Pacific reefs, scientists are not sure what, if anything, should be done about this Grazing Many fish, especially parrotfishes and damselfishes graze intensively on reefs If these grazers are removed, seaweeds can flourish and take over space from corals Many damselfishes act as “farmers,” they pull out unpalatable seaweeds and remove them, and what is left is a dense mat of tasty seaweeds Living Together Coral reefs probably have more examples of symbiosis than any other biological community Symbiotic relationships are very important in coral reef communities Saving coral reefs… Watch the following video clips and write a paragraph in jour Journal on answering the following questions: Why are coral reefs important? What are reef balls? What are some ways of saving the coral reef? Do you think coral reefs should be saved? How can you help? Reef Balls Belize Coral Reef Electric Boost for Reefs Ocean-Saving Coral Reef The End! Thank you for your attention!
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