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Coral Reef Formation By Kurose Coral reefs are called the forest of the sea. Why are coral reefs and forests so important? • Fish, invertebrates (animals without backbones), and algae (seaweed) rely on reefs for food and protection, just as many plants and animals rely on the forest for food and protection. How does a coral reef begin? Coral reefs form when coral larvae (baby form of a polyp) settle on a hard substance in warm, clear, shallow water and begin excreting their skelteons (taking chemicals out of the water to make their hard outer skeleton) It takes millions of coral polyps to make one colony (group of animals that live and work together to survive). It takes tens of thousands to hundreds of thousands of colonies to make a reef. How fast do corals produce skeletons? They only grow a few millimeters a year. What do corals need to keep growing? • Sunlight and nutrients (food they take out of the water that gives them energy to survive and grow) What are the parts of the reef? 1. The inner reef (reef face.) 2. Reef crest (outer edge of the reef flat 3. Reef face (the leading edge of the fringing reef that is always under water) How is a reef flat formed? • As the upper tips of coral are exposed to air too long, they die, leaving a flat surface on the reef -- a reef flat. The reef face (also called the fore reef or reef crest) is the outer ocean edge of a reef. It is where most of the coral growth occurs. This is one of the most important parts of the reef to protect. What happens if corals grow upward too fast? • They will die of exposure during low tides What is a fringing reef? • A fringing reef is a reef that is small and close to an island’s shore. • This is an early stage in coral reef development. Barrier reefs form on an older island. As an island erodes, the original fringing reef is located farther and farther offshore, forming a barrier reef. What is found between a barrier reef and a volcanic island? • Usually a lagoon. What are biological agents of change on a coral reef? • All plants and animals that build-up or destroy a reef are biological agents of change. What are reef-building agents? • Organisms that secrete the calcium carbonate skeletons that form the reef –corals. • Another important reef building agent are corraline algae (seaweeds that have calcium carbonate in their cell walls.) What are crack-filling agents? • Organisms that produce sediments or that live in the cracks & crevices of the reef. • Mollusks, pieces of corals, etc. • These agents fill in the areas between colonies in the reef What are passive agents? • Organisms that use the reef to live and hide in, but that do not affect reef structure. • They may eat or be eaten by other organisms in the reef • Examples: many fish, anemones, crustaceans, worms, many mollusks, etc. What are destructive agents? • Organisms that erode the reef by grinding, chewing, or boring into it. • Example: uhu (parrot fish), wana (sea urchins), ka hoku kai (starfish) What are physical agents of change? • Waves, currents, pollution, moving sand, silt deposits, fresh water, and severe changes in temperature can affect changes on the reef. Reef building corals have a symbiotic relationship with a single celled algae. The small brown dots in the coral polyps in the picture above are a single celled algae (zooxanthellae) A symbiotic relationship is formed when two different species live together and use each other for survival What happens when the reef falls below where sunlight can reach? Why? • The reef dies because algae cells(xoozanthellae) that corals depend on for food and oxygen cannot photosynthesize. How is a coral reef like a forest? Corals are animals that build coral reefs. Reefs provide a place for seaweed to grow, which provides food for many other animals. Reefs provide food and shelter to a variety of sea life. Reefs and forests are both complete communities of many associated plants & animals What are two ways that coral reefs are of environmental and economical importance? • Reefs protect coastlines and beaches from erosion • Reefs form bays and lagoons that provide safety for ships.
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