Ocean Series Coral Reefs

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1 Ocean Series Coral Reefs Coral is part of the animal kingdom, a member of the scientific phylum Cnidaria along with other marine creatures including sea jellies. Sea jellies have a soft gelatinous body while a colony of coral, called a coral reef, has a hard brittle surface. How can two apparently dissimilar animals belong to the same phylum? Coral and sea jellies both have a polyp stage. A sea jelly polyp can spawn hundreds of genetically identical sea jelly offspring and a coral polyp can build a coral reef of genetically identical individual coral. Scuba divers enjoy visiting coral reefs in warm tropical waters and prefer areas where the water is clear. Coral is colorful because certain species of microscopic algae, called zooxanthellae, have a symbiotic relationship with coral polyps. Zooxanthellae provide color and food energy for the coral and create the brittle exoskeleton of coral. Coral reefs attract many species of small tropical fish that can hide from larger predators within the branches of the coral. A coral reef creates its own ecosystem of plants and animals. The largest and most famous warm water coral reef is the Great Barrier Reef off the coast of Australia. The second largest tropical reef in the world exists off the coast of Belize, a country in Central America. Other smaller reefs can be found all around the globe, off the coast of Hawaii, in the Caribbean Sea, in the Persian Gulf, around Indonesia and off the east coast of Africa. Lesser known species of coral exist in deep cold water, even at depths of over 6,000 feet. Only certain species of deep water coral form reef structures. A far cry from the usual perception of coral as existing only in warm shallow tropical waters, one of the largest accumulations of deep water coral is found north of the Artic Circle in Norway and measures about 25 miles long and 2 miles wide. Deep water coral do not have a symbiotic relationship with zooxanthellae. Coral Larvae A coral larva is created by sexual or asexual reproduction, depending on the species of coral. There are two types of sexual reproduction among coral species: spawning and brooding. About 75% of stony coral are broadcast spawning coral species that release eggs and sperm into the ocean water; eggs and sperm mix in the water to form a zygote which then hatches into a microscopic coral larva. The

2 other 25% of stony coral species reproduce by brooding; these species release only male gametes which then sink back into the reef and fertilize stationary eggs. When coral larvae, also called planula, hatch they become part of the mix of larvae floating near the surface of the ocean that are collectively called zooplankton. Zooplankton is an essential part of the marine food chain. Planula larvae of coral are eaten by other sea creatures that filter sea water for plankton food sources. Some species of whales are examples of filter feeders. Planula remain floating in the ocean until environmental cues, such as light, cause them to seek an appropriate substrate. A substrate is simply a suitable surface where the larva can attach and grow. Like other plants and animals, a coral larva of a given species has preferred substrates. The larva will attach when it locates a viable location. The attached larva then begins its development into a coral polyp. Still other coral species reproduce by asexual methods know as budding and fragmentation. These asexual methods result in new coral that are genetically identical to the parent. In budding, a bud, somewhat like the leaf bud on a tree, appears at the base of a coral polyp. This bud grows into a new coral polyp. Fragmentation occurs when some outside event breaks a piece of living coral from the reef. If the broken fragment eventually attaches to a suitable substrate it can begin a new piece of the coral reef in another location. Polyps A coral reef is composed of millions of individual coral polyps. Some species of coral are called hard coral because they create a hard calcium carbonate structure; calcium carbonate is the same material as limestone. Soft coral species are also composed of polyps similar in anatomical structure but do not create an exoskeleton. Polyps attach to a substrate at the base of the polyp, the calyx. A coral polyp has six radial ridges, a characteristic of the Cnidaria phylum. Each polyp has tentacles at the top where the mouth is situated. Coral polyps feed on small fish and zooplankton at night and use stinging nematocysts to stun prey. However, coral obtain approximately 90% of their nutrition from their symbiotic relationship with zooxanthellae. Coral in a colony are interconnected by a system of gastrovascular canals. This intricate mechanism allows food energy generated by

3 zooxanthellae or captured prey to be shared by adjacent polyps for the benefit of the colony.

4 Circle True or False after analyzing each of the following statements. 1. True False Coral are animals, members of the scientific phylum Cnidaria along with other marine creatures including whales. 2. True False When coral reproduce the new polyps are always genetically identical to the parent. 3. True False Tropical coral is colorful because certain species of microscopic algae, called zooxanthellae, have a symbiotic relationship with coral polyps. 4. True False The largest and most famous warm water coral reef in the world exists off the coast of Belize, a country in Central America. 5. True False Deep water coral do not have a symbiotic relationship with zooxanthellae. 6. True False There are two types of sexual reproduction among coral species: spawning and branching. 7. True False Broadcast spawning coral species release eggs and sperm into the ocean water; eggs and sperm mix in the water to form a zygote which then hatches into a microscopic coral larva. 8. True False Coral larvae, also called planula, enter the marine food chain as zooplankton. 9. True False A coral polyp has six radial ridges, a characteristic of the Cnidaria phylum. 10. True False The system of gastrovascular canals in a coral reef allows food energy generated by zooxanthellae to be shared by adjacent polyps.

5 Answers 1. False 2. False 3. True 4. False 5. True 6. False 7. True 8. True 9. True 10. True

Overview. What are Corals?

Overview. What are Corals? Overview Coral Reefs extend back over 500 m.y. Grow in tropical seas with normal salinity Support a great variety of plant and animal life Cover less than 0.2% of sea floor Contain about 25% of marine