Coral reefs are large underwater structures composed of the skeletons of colonial marine invertebrates called coral.
Characteristics:
Characteristics:
- The main frame of the reef is built up by coral polyps - tiny soft-bodied marine organisms that use calcium carbonate dissolved in seawater to build up a hard limestone casing. These live in colonies as layers of corals are built up over time.
- The reef provides a habitat for a plethora of living organisms including algae, fish, sponges and shellfish. Some of these creatures also contribute their skeletons when they die to build up the reef.
- Ocean temperatures must ideally be between 23 and 30 degrees Celsius. Higher temperatures can cause bleaching of corals.
- Sunlight must be able to penetrate so that the coral grows in fairly shallow water.
- The right salinity is also required. This is why reefs are not normally found near the mouths of rivers.
- Corals need to grow in clean, well-aerated water. Murky or turbid water blocks much needed sunlight while silt particles tend to choke the coral polyps.
Types:
- Barrier reefs: are found parallel to the coast and are usually separated by a shallow but wide area of water called a lagoon. The second largest barrier reef in the world is located off the coast of Belize
- Fringing reefs: are low platforms of corals, 0.5 km to 2.5 km. wide, lying close to the shore of an island or continental shelf, but separated by narrow lagoons; its outer edge descends sharply into the sea. It is commonly found in the Caribbean located off the coast of Jamaica, Barbados, Tobago & Antigua
- Atoll reefs: tend to form a Horse shoe. They are usually linked to a sunken volcanic cone.
Importance of coral reefs:
Threats to coral reefs:
Human -
Protection of Coral reefs:
- Functions as a self-repairing breakwater which protects the coast from storm waves and long-term erosion.
- Provides materials for white sandy beaches such as the west coast of Barbados.
- A diverse ecosystem similar to a tropical rainforest. Provides a habitat for many important organisms. The fishing industry benefits from their presence. The pharmaceutical industry also derives material to develop substances such as coral calcium.
- Tourism benefits from these beautiful attractions as people pay to get boat rides and enjoy snorkeling activities on the reefs.
Threats to coral reefs:
Human -
- Destructive fishing practices such as dynamite, cyanide and trawler fishing practices as well as overfishing.
- Shipping - improper disposal of sewage can create algal blooms which grow rapidly at the expense of the coral polyps. Anchors from boats and dredging the sea bed to make way for large ships to dock have devastating effects on the health of corals.
- Oil spills - from rigs or ships can smother corals and the harmful chemicals can cause permanent damage.
- Recreation - coral harvesting, boat anchors and reef walking have caused severe damage to the Buccoo Reef in Tobago.
- 'Natural' threats include global warming (coral bleaching),
- Increased carbon dioxide in seawater (increases the seawater's acidity),
- Sea-level rise due to melting ice-caps (sunlight now has to penetrate through more water to get to the corals),
- Diseases such as White Pox Disease
- Invasive species such a the lionfish that thrive at the expense of the native populations that keep the delicate coral reef ecosystem in balance
Protection of Coral reefs:
- Regulating coastal development
- Educating the public about how they should treat the reefs
- Establishing 'Protected Areas' through legislation
- Protecting excessive beach erosion by building seawalls, groynes, artificial breakwaters and planting mangroves