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Biodiversity of the Caribbean

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Biodiversity of the Caribbean A Learning Resource Prepared For: (Protecting the Eastern Caribbean Region’s Biodiversity Project) Photo supplied by: Andrew Ross (Seascape Caribbean) Part 2 / Section C Coral Reef Ecosystems February 2009 Prepared by Ekos Communications, Inc. Victoria, British Columbia, Canada [Part 2/Section C] Coral Reef Ecosystems Table of Contents C.1. What is a Coral Reef Ecosystem? C.2. Formation of Coral Reefs C.3. Types of Coral Reefs C.4. Species Biodiversity C.5. Importance of Coral Reefs C.5.a. Food Source and Habitat C.5.b. Water Filtration C.5.c. Fisheries C.5.d. Tourism C.5.e. Coastal Protection C.5.f. Source of Scientific Advances C.5.g. Intrinsic Value C.6. Types of Human & Natural Impacts C.6.a. Pollution C.6.b. Over-fishing C.6.c. Tourism C.6.d. Sedimentation C.6.e. Mining Reef Resources C.6.f. Climate Change C.7. Protecting Coral Reefs C.8. Student Fact Sheet: Fifty Facts About Wider Caribbean Coral Reefs C.9. Case Study: Tobago Cays Marine Park (TCMP), Southern Grenadines C.10. Activity 1: Mock Marine Management Plan C.11. Activity 2: Coral Reef Ecosystem Poster Presentation C.12. Case Study: Community-Based Natural Resource Management in the Bay Islands, Honduras C.13. Activity 3: Diagram the Case! C.14. References [Part 2/Section C] Coral Reef Ecosystems C.1. What is a Coral Reef Ecosystem? 30°C. Tropical corals are found within three main regions of the Coral reefs exist in the warm, clear, shallow waters of tropical world: the Indo-Pacific, the Western North Atlantic, and the Red oceans worldwide but also in the cold waters of the deep seas. Sea. The Western North Atlantic region contains the second most For the purpose of this section, the marine, warm water coral coral reefs (after the Indo-Pacific) and includes the coral reefs reefs will be discussed. within the Caribbean. Types of Corals There are two main types of corals: hard corals composed of C.2. Formation of Coral Reefs stony calcium carbonate, and soft corals composed of a protein Coral reefs are formed by the work of tiny organisms known as and calcium carbonate material. Solid corals, or Scleractinians, coral polyps. A coral polyp consists of a fleshy sack with a ring including brain, star, staghorn, elkhorn, and pillar corals have of tentacles that sits in a limestone skeletal case, secreted by the rigid exoskeletons that protect their soft interiors. Soft corals, or polyp. Thousands of coral polyps develop together and create a Gorgonians, including sea fans, sea whips, and sea rods, sway structure of limestone (calcium carbonate or CaCO3). The prime with the ocean currents and lack a stony exoskeleton. reef builders are the stony or hard corals (Anthozoa species). The bulk of any reef colony is composed of nonliving matter. It 4 Tropical coral reefs occupy less than one percent of the Earth’s is only the upper layer that is living cora l. While corals are the marine environment, but are home to more than a quarter of all chief architects of reef structure, they are not the only builders. known marine fish species and tens of thousands of other species Coralline algae cement various corals together with compounds found nowhere else on earth1. The total area of the world’s tropi- of calcium, and other organisms such as tube worms and mol- 5 cal coral reefs is around 284,300km². 2 Of the total amount of luscs donate their hard skeletons . Tropical coral reefs can grow coral reefs in the world, 7.64% of it is located within the Carib- upwards at rates of 1centimetre to 100 centimetres per year. bean Sea Large Marine Ecosystem3. This is in contrast to deep sea corals which grow a mere 5 to 25 millimetres each year. For both coral types, over time they form Factors Necessary for the Formation of extensive reefs. Coral Reefs Reef-building corals have evolved an essential symbiotic Geographically, tropical coral reefs lie between the latitudes of relationship with a type of brown algae called zooxanthellae 30 degrees north and south where sea temperatures are warmest. (Symbiodinium microadriaticum). A symbiotic relationship ex- Tropical coral reefs require water temperatures between 18°C and ists where two or more organisms co-exist together in a mutually advantageous relation- ship, with both deriv- ing benefits from each other. Millions of these single-celled algae are living as symbionts within their tissues of corals. Zooxanthellae produce sugars and oxygen through photo- synthesis which helps the coral in the process of producing limestone or calcium carbonate. With this assistance by zooxanthellae, corals grow up to three times faster. It is also the zooxanthellae, which give the corals their characteristic greenish color. In the case of a change in environmen- tal conditions, such as increased temperatures or changes in salinity, World Resources Institute. (2004). Reefs at risk in the Caribbean. Retrieved from: arthtrends.wri.org/features/view_feature.php?fid=55&theme=1 the coral polyps may expel the algae. Without [Part 2/Section C] Coral Reef Ecosystems Zubi, T. (2008). Coral reef ecology. Retrieved from: starfish.ch/reef/reef.html algae, the coral becomes completely white in colour and is con- Coral reefs rank among the largest and oldest sidered bleached. If the coral retains some algae it may survive, living communities of plants and animals on but if bleaching occurs the coral is considered dead. Earth, with the most established coral reefs be- 6 ginning to grow 5000-10,000 years ago . Tropical corals require access to sunlight to survive. The algae living in their cells require light for photosynthesis. Because of this, the water where they grow needs to be shallow and clear. High levels of sediment in the water can smother the coral pol- yps. Corals also require salt water, and the lowering of salinity in their marine habitat can kill them. Essentially, coral development occurs away from river mouths and other sources of fresh water. C.3. Types of Coral Reefs There are four different types of coral reefs: fringing reefs, platform reefs, barrier reefs, and atolls. Reefs that grow in shallow waters are classified as fringing reefs. These reefs border the coast of tropical islands or continents closely or are separated from the coast by a narrow stretch of water. Fringing reefs are generally narrow platforms a short distance from shore and don’t contain a substantial lagoon. Fringing coral reef communities are found in places on the shores of most of the islands in the Eastern Caribbean. Platform reefs develop in sheltered seas, but quite far offshore. They are flat-topped with small and shallow lagoons. Barrier reefs are reefs that are grow parallel to the coast but are separated from land by a lagoon. As the reef continues to grow and moves further offshore, it eventually reaches the edge of the continental shelf (the region of relatively shallow water sur- Photo supplied by: Andrew Ross (Seascape Caribbean) rounding every continent). Barrier reefs can originate offshore if [Part 2/Section C] Coral Reef Ecosystems Coral Reefs in Belize the depth of the seabed is shallow enough to give corals sufficient light to develop. The two largest barrier reefs are the Great Barri- Belize boasts the second largest continuous reef system in the er Reef in Australia, which stretches over 2300 kilometres off the Western Hemisphere, second only to Australia’s Great Bar- coast of Queensland in northeast Australia, and the Mesoameri- rier Reef. The reef of Belize stretches 250 kms along the entire can reef in the Caribbean, which stretches nearly 250 kilometres length of the country and it encloses an approximately 6000 sq. from the northern tip of Mexico’s Yucatan Peninsula to the Bay km lagoon. Islands in northern Honduras. Atolls are rings of reef, often encircling an island of sand and coral rubble. They typically have a shallow, sandy, sheltered la- goon in the centre and access to the open sea is through a number of channels. These channels provide fresh, colder water to the inside lagoons. Coral atolls begin as fringing reefs around active oceanic volcanoes. After volcanic eruptions cease, an island remains. Over long geologic periods, fringing coral continues to grow and develop into a circular coral reef, which is known as an atoll. Barrier Reef Atoll Fringing Reef Platform Reef Zubi, T. (2008). Coral reef ecology. Retrieved from: starfish.ch/reef/reef.html [Part 2/Section C] Coral Reef Ecosystems C.4. Species Biodiversity (Carangidae) and snappers (Lutjanidae), as well as the Caribbean Coral reefs are one of the most biodiversity-rich ecosystems in reef shark (Carcharhinus perezii), come into coral reefs to prey the world. The Caribbean boasts the highest coral reef diversity on smaller fish species. in the Atlantic Ocean due to its geographic isolation from other oceanic regions7. Staghorn coral (Acropora cervicornis) and elkhorn coral (Acropora palmata) are among the dominant spe- C.5. Importance of Coral Reefs cies living on modern Caribbean reefs. They are particularly fast Coral reefs are often referred to as the “rainforests of the oceans.” growing and able to cope both with damage caused by hurricanes This name is attached to this ecosystem as a result of its role in and by rapid changes in sea level. providing habitat and food for an extensive number of species. Coral reefs host an extraordinary variety of marine plants and Caribbean reefs also house lettuce coral (Agaricia lamarki), star animals (perhaps up to 2 million) including one quarter of all coral (Montastrea faveolata), brain coral (Colpophyllia natans), marine fish species.
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