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Coral reefs are complex structures formed by a diversity of different marine organisms. The limestone composition of coral reefs is quite resistant to waves action and tides, and also very rigid. However, they are very fragile to changes in the ecosystem. It is estimated that 27% of the entire coral reefs around the word have already been irreversibly degraded due global warming and anthropic actions; such as the irregular coastal development and pollution.

Coral reefs occur in coastal areas with clear, warm and shallow waters around the tropics. They are extremely important ecosystems for thousands of people. Most depend on them for fishing, tourism, and also due their great biodiversity with numerous fish, crustaceans and other marine animals. Coral reefs are also vital for the coast line, offering protection to coastal systems acting as a natural barrier to the tides.

Coral reefs are ancient formations constituted of calcium carbonate produced by small soft- bodied animals, called "polyps" (they may have less than a cm in diameter). With a tubular body the polyp builds a kind of calcareous shell which lodges forming, together with other billion polyps calls colonies that make up the limestone reef structure. Along with polyps a tiny algae called "zooxanthellae" ends up giving the typical characteristic of corals; their colours that vary from green, blue, yellow, lilac and many others.

An extremely important association for coral reefs is the symbiosis that occurs between corals species and algae; known as zooxanthellae. These algae live within the tissues of reef builders performing photosynthesis and releasing nutritious organic compounds for corals. In turn, the zooxanthellae survive and grow using the products generated by the coral metabolism, such as carbon dioxide, nitrogen and phosphorus compounds. The coral nutritional needs are largely supplied by the zooxanthellae. They are also involved in the secretion of calcium and formation of the coral skeleton. Although coral species are found in virtually all oceans and latitudes, species of reef builders (hermatypic corals) are restricted to tropical and subtropical regions. The reefs generally require hot and clear water (25 – 30 °C) away from the influence of fresh water. The pollution (sewage, oil spills and others) and sedimentation (terrigenous silt carried to sea due to deforestation and earthworks) endanger many coral reefs systems, including the numerous other organisms that depend on them (including human communities that live from fishing and collecting reef marine animals). An apparently recent phenomenon - not yet fully well understood by researchers - that has occurred in all reef regions of the world is the coral bleaching. This is basically the loss of the zooxanthellae from the coral tissue. As the colour of most host coral skeletons is largely depended from the symbiotic "algae", their tissues become pale or white. In some cases, the coral tissues can be almost transparent, revealing the underlying white skeleton.

It is estimated that coral reefs cover around 284,300 km², with the Indo-Pacific region (Red Sea, Indian Ocean, Southeast Asia and the Pacific Ocean) contributing with 91.9% of this total. Atlantic Ocean and the Caribbean contribute with around 7.6% of the total. The Northeast Brazil is the only region of the South Atlantic Ocean that has reef formations that are distributed throughout the Northeast coast and therefore must be protected.

Projeto Conservação Recifal