page_title: Réunion's coral reef
section_title: Environment and threats
hierarchical_section_title: Réunion's coral reef / Environment and threats
caption_attribution_description: English: Blenniella cyanostigma in a pool on the shore of Réunion island Français&#160;: Cabot sauteur (Blenniella cyanostigma) dans une flaque à la Pointe au Sel (Saint-Leu, île de La Réunion)
context_page_description: Réunion is an island located near the eastern coast of Madagascar in the Indian Ocean. Its coral reef covers a concentrated part of the western littoral. The coral reef is located between St Leu and St Gilles. It is more than 9 kilometres long and ranges in width from 50 metres in its northern part at St. Gilles to 600 metres in the south. Since the island is distant from the continental shelf, the sea becomes deep not far from the coast. The presence of nearby deeper ocean currents supports a rich biodiversity fauna and flora in the reef environment.
context_section_description: Coral reefs are among the most densely populated marine environments. The coral reef fringing Réunion is a rich habitat for soft and hard corals that provide food and habitat for an abundance of fish and shellfish. The corals feed on a diet of plankton and algae which they catch with their tentacles. The growth cycle of corals is relatively slow, with growth of about 10 centimetres (3.9 in) per year. Male corals disseminate sperm cells into the water, which fertilize free-floating eggs released by the female corals. Reproduction is limited due to the proportionately small number of male corals.
  The integrity of Réunion's reef has recently become threatened by an increase in pollution and human exploitation of the ecologically-sensitive marine life. Ocean water quality and the health of coral species are both symbiotic and reflexive; polluted water negatively impacts the health of coral reefs, and unhealthy reefs add to the degradation of ocean water quality. Studies show that ocean pollution inhibits coral growth and therefore contributes to algal blooms, which result in hypoxic conditions for coral reefs.
  Coral is very sensitive to variations in water temperature. The effects of global warming on oceans have a direct impact on the health of coral reefs. The optimal water temperature for coral at Réunion is between 23 °C and 28 °C. Increased surface water temperature related to global warming can contribute to disease and bleaching of coral reefs, as is apparent on Réunion.
  Natural cyclones and anthropogenic disturbances such as urban development of catchment areas affect the reefs of Réunion. These ecological disturbances have led to an increase in coral reef nutrient levels via submarine groundwater discharge. Increased nutrient levels have resulted in the modification of flora and fauna in the benthic zone. The coral reef is a natural barrier that protects the coast from typhoons.
caption: Blenniella
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