Coral Reefs

What is a coral reef?

Coral reefs are biogenic structures that are ancient even by geological standards; the oldest species of corals are over 450 million years old. The spectacular longevity of corals is a testament to the adaptability of the coral animal, as it has survived gradual but radical climatic and geologic changes during their long tenure on earth. The reef structure itself is the product of biologically mediated calcium carbonate production of the small, individual coral polyp. Text courtesy of IOC

The coral reef ecosystem

Coral reefs flourish in shallow, tropical waters that are clear and nutrient poor (oligotrophic). "Occurring almost exclusively between 30 deg N and 30 deg S, they are concentrated in four large tracts: the Red Sea and the western Indian Ocean, the Indian Ocean and the western Pacific Ocean, the south Pacific Ocean, and the Caribbean Sea and western Atlantic Ocean" (Coral World, National Geographic, 2000). Despite the oligotrophic waters, coral reefs create a highly productive, and very efficient, ecosystem. From the photosynthetic algae that live symbiotically within the coral polyps, to the sharks that hunt fish along the reefs, coral reefs support an extremely biodiverse community of marine life. Text courtesy of IOC

Threats to Coral Reefs

Although coral reefs have survived in the earth's oceans for over 450 million years, they remain highly sensitive to rapid climatic changes and anthropogenic pressures. Presently, the biggest threats to coral health are
  • global warming, and corresponding sea level and sea temperature rise (which can result in coral bleaching)
  • sedimentation and pollution
  • overfishing and
  • unsustainable and destructive extraction techniques.
Furthermore, coral reefs are very valuable not only ecologically, but to the human population as well. Text courtesy of IOC. The new book "Reefs at Risk. Revisited" 2010 is now available.

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