Distribution & Features of Coral Reefs
Distribution of Coral Reefs
- Coral reefs are large deposits of calcium carbonate built entirely of living organisms called coral polyps
- Corals are scattered throughout the tropical and subtropical Western Atlantic and Indo-Pacific oceans, generally within 30°N and 30°S latitudes
- Western Atlantic reefs include these areas: Bermuda, the Bahamas, the Caribbean Islands, Belize, Florida, and the Gulf of Mexico
- The Indo-Pacific ocean region extends from the Red Sea and the Persian Gulf through the Indian and Pacific Oceans to the western coast of Panama
- Corals grow on rocky outcrops in some areas of the Gulf of California
- The Great Barrier Reef in northern Australia is renowned for its great biodiversity and size and can be seen from space
- Their distribution is controlled by four factors:
- Temperature
- Light
- Water depth
- Salinity
What are the features of Coral Reefs?
Main Features of Coral Reefs
Global Features | |
Temperature | Corals cannot tolerate water temperatures below 18°C but grow best at 23°C – 29°C. Some can stand temperatures as high as 40° C for short periods. This is why coral reefs normally grow between the Tropic of Capricorn and the Tropic of Cancer |
Light | Corals need light for photosynthesis due to the algae, called zooxanthellae, that live in their tissue |
Water | Corals are generally found at depths of less than 25m where sunlight can penetrate. The water must also be clear and clean to allow for optimum photosynthesis to occur |
Salinity | Since corals are marine animals they need salty water to survive, ranging from 32-42% saltwater |
- At a local level, other factors will affect development:
- Wave action - corals need well-oxygenated, clean water and wave action provides this
- Exposure to air - although corals need oxygenated water, they cannot be exposed to air for too long or they will die
- Sediment - all corals need clear, clean water. Any sediment in the water will block normal feeding patterns by reducing the availability of light affecting the photosynthesis of the microscopic algae 'zooxanthellae' living in polyp tissue. The corals provide algae with a home and compounds for photosynthesis. In return, the algae produce food, and oxygen and help remove wastes
Types of Coral Reefs
- Fringing Reefs - these are reefs that form around a land mass
- Barrier Reefs - these are found parallel to the shore but are separated by a channel of water:
- The Great Barrier Reef in the Coral Sea, off the coast of Queensland, Australia is a good example of a barrier reef.
- It is the world's largest coral reef system with over 2,900 individual reefs and 600 islands that stretch for over 2,300 kilometres and can be seen from space
- Atolls - horseshoe-shaped rings, consisting of a coral rim that encircles a lagoon