Mauritius is almost completely encircled by fringing reefs, with substantial lagoon and barrier reef development on the east and southwest coasts. The lagoons are dominated by algae, but with some areas of seagrass. The reef slopes have a clear spur and groove zone. Below about 20 meters there is usually only a thin veneer of coral rock overlying volcanic rocks. Rodrigues is the oldest of the volcanic islands and has a highly developed reef structure, although a true barrier reef has not formed. The island is totally encircled by reefs, with wide shallow reef flats extending out from the shore – in the east this narrows to 50 meters in places but is more typically 1-2 kilometers wide, while at its widest extent in the west it reaches 10 kilometers. Seagrasses are widespread in the lagoon, and reef flats and mangrove communities are reported to be increasing. The outer slopes are steep, and have 50-70 percent coral cover. In Mauritius the 1998 bleaching event affected 30-40 percent of corals, though very few died. The high rates of survival have, in part, been related to overcast and windy conditions for much of February and March, which were associated with cyclone Anacelle and which mitigated the warming impacts observed elsewhere in the region.

Many of the reefs around Mauritius have been degraded by human activities. Problems include high levels of sedimentation and pollution arising from the clearance of the forest and subsequent agricultural runoff. Further pollution comes from domestic and light industrial effluents. There has also been direct damage to the reefs – blast fishing was a problem in the past and anchor damage continues. Large areas are also affected by crown-of-thorns starfish, which have undergone population explosions since the early 1980s. Tourism is a critical sector of the economy, and Mauritius had 487 000 arrivals in 1996. Coastal development to cater for this industry has added significant impacts, notably through pollution, but also through coral and shell collection for sale to tourists as well as direct diver impacts.

By contrast the island of Rodrigues remains relatively undeveloped, with a small human population. Fisheries are an important industry and there is a well developed octopus fishery which exports to Mauritius. Tourism is a small, but growing, sector of the economy, with some 26 000 visitors in 1997. Soil erosion and sedimentation are still a problem around this island, but overall the reefs, which are further offshore, remain in relatively healthy condition.

Mauritius holds jurisdiction over a string of islands and reefs running north along the Mascarene Ridge – the northernmost island is Albatross, although there are reef communities on the Nazareth Bank some 240 kilometers further north (and still within Mauritian waters). The main group of islands and reefs in this area lie on a long reef structure on the Cargados Carajos Bank. These include St. Brandon (North Island), St. Raphael, Île Perle, Île Frégate and Île Paul, plus a chain of over a dozen islands in the south. There is little published information about these reefs, however they are thought to include a broad reef flat and possibly the largest continuous algal ridge in the Indian Ocean. There are large and important seabird colonies on a number of islands. The islands are leased to a private fishing company which is based, along with a meteorological station, on St. Raphael.

Also administered by Mauritius is the isolated Agelaga, a complex of two islands (North and South Island) and a substantial reef area. Again there is very little published literature describing this island.

Mauritius has a coastline of 200 km with 243 km² of lagoon area enclosed by 150 km of fringing reef that almost completely surrounds the island, except at major river mouths and on the south and west coasts. Mauritius has rich coral diversity with a total of 159 hard corals in 43 genera. Recent coral bleaching in 2003-2004 affected some corals; however the reefs have since recovered and new recruits are increasing, especially on the reef slopes. The back reef is mostly dominated by branching and tabular Acropora, whereas encrusting corals dominate the fore-reef. Algae have been observed seasonally and a few soft corals and other colonial animals such as zoanthids are relatively common. The physico-chemical and bacteriological parameters are within the Coastal Water Quality Guidelines at all sites. The major threats to coral reefs are cyclones, coral diseases, crown-of-thorns starfish, coral bleaching and human damage from extensive coastal development, land-based pollution, sewage outfalls and anchor damage.