Mauritius Marine Conservation Society – MMCS
CORAL REEFS
Coral reefs occupy less than 0.1% of the ocean floor, but they rival the rainforest in terms of biodiversity as they are highly complex ecosystems. They support nearly 25% of all known marine species. They are most commonly found at shallow depths in tropical waters, but deep water and cold water corals also exist on smaller scales in other areas. Constructed by living organisms, coral reefs are home to some of the most fascinating plants and animals in the world.
Introduction
These ecosystems have huge ecological and social value, providing food and income for millions of people worldwide. They also protect coastal communities from damaging storms and cyclones.
Coral reefs are very fragile, partly because they are very sensitive to water temperature. They are under threat from various tourism activities, overfishing or damaging fishing techniques, climate change, oceanic acidification, agricultural runoff and water pollution, to name a few.
Monitoring and Survey
For the island states in the south west Indian Ocean, coral reefs represent an important source of revenue on which the fishery and tourism sectors are dependent. They constitute a very productive but vulnerable ecosystem, which indicates the health status of the lagoons and coastal regions as a whole.
The follow up of the project is supervised by the Regional Environment Programme, Indian Ocean Commission and the European Union. It forms part of the “Gestion Intégrée de la Zone Côtière (Integrated Coastal Zone Management)” program, at a national and regional level, taking into consideration all the people involved in this area. All this in order to reach a harmonious and sustainable utilisation of marine resources.
These actions are conducted jointly by state bodies, para-statal organisations and local NGOs.
The sampling methods used are an adaptation of those used by international networks for the follow up of coral reefs (Global Coral Reef Monitoring Network). Their objectives are: the establishment of a punctual health status of the reefs as well as the follow up of the evolution of this ecosystem and a study on the impact of natural and anthropogenic factors on the zone.
The techniques used are founded based on non-destructive observation methods which avoid disturbing the biosphere (living environment) of populations already living there. These are: exploration by freediving, linear transects and quadrat techniques.
For each island of the Indian Ocean Commission, study zones have been defined according to criterias specific to each country. In Mauritius, five sectors have been established around the island: Albion (west), Pointe aux Sables (west), Anse la Raie (north-north-east), Bambous Virieux (east) and Blue Bay (south east). The MMCS is reponsible for the Anse la Raie sector.
South west coast
A follow up of the coral reefs of the south west coast was started in September 2008 as part of the “Sustainable Management of Marine Resources, Cetaceans-Reefs in Mauritius” project.
Due to the invaluable cooperation from the divers from Mauritius Underwater Group (MUG), Mauritian Scuba Diving Association (MSDA), in partnership with ARVAM (Agence pour la Recherche et la Valorisation Marine), samplings could be done on 22 stations located on the outer slope of the coral reefs on the south west coast of Mauritius.
The data collected on coral recovery have been processed and analysed and then integrated in order to establish GIS maps of the western region of Mauritius. The next step is to use this data to support the creation of a Marine Protected Area (MPA) in this region.
Survey Reports from Anse la Raie
Anse la Raie, a windy region, is located in the north-north-east of Mauritius, in a zone which has been undergoing important coastal developments.
The reef being studied is that of Calodyne, close to the shorline, located on the east of the Oscorne channel. Following the non-scuba dive based exploration works undertaken on the reef area, a site best representing the diversity of this field had been chosen. The site is comprised of a reef station about 1 – 1.5 metres deep, and an “outer slope” station about 6 – 8 metres deep, each representing different habitats.
The frequency of follow ups of the stations is annual or semestrial. However, after an exceptional event such as a cyclone, a catastrophic pollution, a study of the direct impact must be done.
The parameters considered are physico-chemical (temperature, salinity, luminosity, meteorology) and biological (the benthos, or organisms linked to sea beds, and fishes that are bio-indicators of the health status of the reef and the fishing pressures).
The organisms are identified by using a predefined coding, benthic colonisation and substrates (elements that constitute the bottom), as well as fishes.
The observations are carried out in intervals by free diving on the reef station and by scuba diving on the external slope. The method used to explore the stations is that of linear transects.