Coral Reefs - Spatial Patterns
Where are coral reefs found?
Special conditions are needed for reef-building corals. Coral reefs will only grow in waters warmer than 18oC, and no deeper than 50metres. Therefore coral reefs are limited to clear, shallow tropical seas found either side of the equator. Corals may not develop properly in waters that receive freshwater runoff or sediments from rivers.
Special conditions are needed for reef-building corals. Coral reefs will only grow in waters warmer than 18oC, and no deeper than 50metres. Therefore coral reefs are limited to clear, shallow tropical seas found either side of the equator. Corals may not develop properly in waters that receive freshwater runoff or sediments from rivers.
Location
Altitude
Latitude
Size
Shape
Barrier (Ribbon) Reefs: run parallel to the coastline in a ribbon shape. They create a barrier between the shoreline and the open sea.
Patch reefs: oval in shape and grow outwards
Fringing reefs: formations linked to the coastline
Atolls: ring-shaped coral islands
Coral Cays: various shapes - based on sand banks - can be changed/swept away by cyclones or by currents.
Continuity
Many types of coral reefs require a solid land mass for the ecosystem to develop. As such there is some coninuity around large landmasses, however in many island areas (e.g Indonesia, Pacific Islands), coral reef ecosystems can be separated by many miles from the next reef.
Barrier Reefs are rarely continuous - they have open channels, some of which can be extremely large.
- Reefs tend to be most extensively developed along the eastern edges of continents which are bathed in warm equatorial currents.
- Turbidity and salinity restrain coral growth. Muddy waters along coast lines at the point of the river mouths dampen coral reef growth.
- A common place for coral reefs to grow is around volcanic islands in tropical waters. When the volcano first forms corals begin to accumulate on the upper part of the volcano in the shallow water. This process often forms fringing reefs attached to the side of the volcano (keep in mind that fringing reefs can also form in other locations). The coral continues to grow upwards and over time the volcano sinks. When the volcano has sunk the coral will form a coral ring with a lagoon in the centre. When the volcano has completely sunk below the water's surface, the no land can be seen it now becomes an atoll.
Altitude
- Coral reefs are found below sea level, in shallow, warm water (temperature and light intensity are important factors in their growth).
- Water temperature decreases with water depth an as such coral reefs tend to be limited to the sunlit waters of the upper 30m of water. The presence of photosynthetic zooxanthellae in the coral's flesh effectively limits the coral growth to the upper zone of water.
Latitude
- Coral reefs are located in tropical and subtropical areas of the world with decreasing species diversity with increasing latitude (between the Toprical of Cancer and the Tropic of Capricorn).
Size
- Coral reefs cover less than 1% of the oceans floor.
Shape
- The shape of a coral reef is determined by the type of coral reef. Types of coral reefs and their shapes are as follow:
Barrier (Ribbon) Reefs: run parallel to the coastline in a ribbon shape. They create a barrier between the shoreline and the open sea.
Patch reefs: oval in shape and grow outwards
Fringing reefs: formations linked to the coastline
Atolls: ring-shaped coral islands
Coral Cays: various shapes - based on sand banks - can be changed/swept away by cyclones or by currents.
Continuity
Many types of coral reefs require a solid land mass for the ecosystem to develop. As such there is some coninuity around large landmasses, however in many island areas (e.g Indonesia, Pacific Islands), coral reef ecosystems can be separated by many miles from the next reef.
Barrier Reefs are rarely continuous - they have open channels, some of which can be extremely large.
Great Barrier Reef
- stretches 2000 kilometres along the east coast of Queensland from just above Fraser Island at latitude 24 degrees S to near the mouth of the Fly River in the Gulf of Papua New Guinea, at around 8 degrees S.
- covers 348,000 kilometres
- It is not a single structure, but a collection of over 2000 reefs, including barrier reefs, fringing reefs, islands and cays.
Coral Triangle
- located in the western Pacific Ocean
- includes the waters of Indonesia, Malaysia, Papua New Guinea, the Philippines, the Solomon Islands, and Timor Leste.
