"La Route du Corail"

A coral reef is a natural and bioconstructed structure of mainly corals that develop their own mineral substrate. At the national level, it represents the marine ecosystem with the most important biodiversity, about 25% of the species of all marine life. Beyond this ecological interest, the coral reef is at the heart of economic, social and environmental issues. First, it is a bulwark against the violence of the sea and helps protect the coast by absorbing the energy of the waves, mainly in regions where hurricanes hit. Finally, it is important to note that marine tourism is a very important economic source (Figure 1) and is one of the major development issues for most French overseas departments and territories; for example, in Reunion island, diving is the second most popular sport activity.

Unfortunately, these marine organisms have been threatened since the 1980s and regress strongly. According to IFRECOR (the French Initiative for Coral Reef), 60% of coral reefs are threatened worldwide and by the middle of the century 75% could be reached, representing a critical threat of extinction. There are different threats to corals, the main one being pollution. The release of organic elements in large quantities, from poorly treated waters, promotes the development of algae at the expense of building corals. Releases of pesticides and herbicides also contribute to the disappearance of coral symbiotic algae, essential for their survival. Climate change is just behind pollution in the disappearance of corals. The increase in water temperature leads to bleaching, potentially leading to the death of coral (Figure 2). Coastal urbanization, intensive agriculture and clearing are also causes of soil erosion, leading to erosion of the coast and thus sediment choking of the reefs. Finally, it is impossible to turn a blind eye to the impact of overexploitation of resources with overfishing and poaching of endangered species.

Reef Check is an international organization that complements the scientific monitoring actions conducted as part of the Global Coral Reef Monitoring Network (GCRMN). As shown in Figure 3 below, this organization shines in the world, as for example in Australia, Guadeloupe, French Polynesia, La Réunion... It is active in more than 40 countries and territories of the tropical zone and has set multiple goals being:

• Educating the public and governments about the value of coral ecosystems
• Promoting local actions for the protection and rehabilitation of reefs
• The impetus of a global network of volunteers, trained and led by scientists, to monitor and inform the health of the reefs through a simple method accessible to any diver
• Facilitating the collaborative use of information by community, government, academic and business groups to develop ecologically effective and economically viable solutions

This organization is a coral reef conservation program. The latter is based on volunteering and the principle of voluntary participation. Hundreds of scientists and thousands of divers around the world are involved in this program. Reef Check is headquartered at the Institute of Environment at the University of California, Los Angeles. In each country participating in the program, there is a national coordinator and one or more teams.

If we are more interested in Réunion Island, the Reef Check program has been developed since 2003 by the ARVAM (Agency for Marine Research and Development). It involves the various volunteers in the coral reef health survey and assessment, in the company of a scientist.

As mentioned above, coral survival is endangered by a variety of threats. However, given the importance of corals, it was decided to conduct research on their health and then propose solutions in links. "La Route du Corail" is a project that is set up by Reef Check to assess the health of the reef in the Reunion island. In January 2018 should take place " La Route du Corail " in Saint-Leu.