Coral Reefs By Laura Leyda and Jennifer EnglerBy Laura Leyda and Jennifer Engler

Coral reefs are warm, clear, shallow ocean habitats that are rich in life. Coral reefs are among the most biologically diverse regions on Earth. Even though they cover only a tiny fraction (less than.2 percent) of the ocean's bottom, coral reefs contain more than 25 percent of all marine life.

What is coral? Coral are cousins to jellyfish and anemones (Cnidarians) Corals (tiny animals, called polyps) secrete a stony cup of limestone around themselves as a skeleton The polyp absorbs calcium carbonate out of the water and use the calcium carbonate to build the reef Millions of polyps work together in a cooperative colony generation after generation to create the limestone skeletons that form the framework of the coral reef. Have been in existence about 200 million years.

2 Types of Reproduction: Asexual and Sexual Reproduction Asexual reproduction in corals is called budding. Sexual reproduction is called spawning. This is a hydra (cousin to coral) with two buds. One bud (on the right) is older than the other.

How Do Corals Eat? Option One: Mutualistic Relationship Inside polyps live zooxanthellae (algae). Zooxanthellae give corals their color and can provide food. Since algae are plants, they photosynthesize. This gives off oxygen as a by-product that is used by the host polyp. Coral provide the algae with carbon dioxide and a safe, protected home.

How Do Corals Eat? Option Two: Soft bodied carnivores with stinging tentacles around their mouth. Coral polyps come out of their skeletons to feed, catching tiny floating animals known as zooplankton. Tentacles release stinging cells (nematocysts) when something brushes by them, stunning the food and bringing it back towards the mouth.

Essentials of Coral Reefs Warm Water : Grow mainly in warm tropical areas (ideally between 70-85°F) between Tropic of Cancer and Tropic of Capricorn. Most diverse is the Great Barrier Reef in Australia - over 3000 different plants and animals.

Essentials of Coral Reefs Sunlight: Corals need to grow in shallow water where sunlight can reach them. Corals rarely develop in water deeper than 165 feet (50 m). Clear Water: Corals need clear water that lets sunlight through to survive. Salt Water: Corals need saltwater to survive and require a certain balance in the ratio of salt to water. This is why corals don't live in areas where rivers drain fresh water into the ocean.

Essentials of Coral Reefs Clean water: Corals are sensitive to pollution and sediments. Sediments can settle on coral, blocking out sunlight and smothering coral polyps. Pollution from sewage and fertilizers increase nutrient levels in the water, harming corals.

Types of Reefs Fringing Reef – lie around islands & continents Barrier Reef – grow on the edge of continental shelves and also are separated from shorelines by lagoons Atolls – a central lagoon and are circular or sub-circular. Formed from subsiding underwater volcano (seamount).

Why are reefs important? Biodiversity As a food resource Source of economic wealth Medicinal use

Why are reefs important? Medicinal use: Coral reefs are sometimes considered the medicine cabinets of the 21st century. Coral reef plants and animals are important sources of new medicines being developed to treat cancer, arthritis, human bacterial infections, Alzheimer’s disease, heart disease, viruses, and other diseases. In the future, coral reef ecosystems could represent an increasingly important source of medical treatments, nutritional supplements, pesticides, cosmetics, and other commercial products.

Threats: Coastal Development Dredging Construction materials Building on reefs Unregulated tourism

Threats: Tourism/Recreation corals easily broken by trampling when people walk out to the reef snorkelers and divers may kill polyps simply by touching coral colonies debris left from tourists

Threats: Marine Pollution Oil spills and discharge of oily ballast water Large power plants change water temperatures by discharging extremely hot water into the coastal water.

Threats: Inland Pollution Erosion from increased forest clearing & intense agriculture causes silt to wash into water, clouding it, and suffocating the coral. Sewage & agricultural fertilizer runoff increases nutrients in ocean, which produces more seaweed that hurts the coral.

Threats of Coral Bleaching Greenhouse Effect - may cause increases in sea temperature Sea water that becomes too warm causes corals to turn white, or bleach; a reaction that occurs if coral polyps are stressed.

Threats: Overfishing Removal of reef fish causes ecosystems to be unbalanced. Due to decreased yields, fishermen forced to change methods to catch enough fish to sustain needs: Fishing with cyanide Blast Fishing **Not only do these practices kill all fish in the affected areas but they also severely damage the corals.

Threats: Overexploitation Corals are popular as decorations, jewelry, and souvenirs. Coral is also mined: Used to build houses and make roads, or is burnt to make lime. Used in aquariums.

Threats: Natural Disturbances Destroyed by hurricanes and tropical storms. Diseases, such as black- band disease – spreads over colonies, progressively killing the polyps. The crown-of-thorns sea stars feeds on corals, if many, can reduce a reef to a mass of dead coral skeletons quickly. step-beyond-crown-of-thorns-starfish-video.htm

Disturbing Facts 58% of the world’s reefs are at risk from human activities 90% of reefs are overfished Almost two-thirds of Caribbean reefs are threatened 40 countries contain no protected reef areas

Preserving Coral Reefs