Cyclones can cause considerable damage. In 1948, Il aux Fous disappeared and Avoquer was submerged by two meters of water. Petit ile Longue was swept away in a later cyclone, but is now reappearing. The South Equatorial Current is dominant. List of named islands Ecology Cargados comprises about of reefs. It has one of the largest algal ridges in the Indian Ocean. Coconut trees can be found on a few islands as well as a variety of bushes and grass. The islands are covered with white granular sand from eroded coral, and a thick layer of guano can be found in most places. The western part of the bay has a coral bank and a fringing reef, dominated by staghorn Acropora, with an irregular front which merges with the coral banks; the reef flat has appreciable coral cover. North of this, or deeper into the bay, are several isolated patches of coral growing in deeper water. The eastern border has reefs with a greater diversity of corals, in particular, enormous hillocks of Pavona with Mycedium tenuicostatum which is unusual in Mauritius. On the sandy substrate, Goniopora and Pontes provide hard substrate for several other species, notably Acropora and Pavona. Large tabular Acropora corals are also conspicuous, and when dead or overturned, provide substrate for other colonizers. These patches have expanded and fused to provide the numerous, large coral banks found in the Bay. Only twenty-eight coral species have been recorded which is probably due to the uniform habitat. Further offshore lies a peripheral fringing reef. This complex of low islands, coral reefs and sand banks arises from a vast shallow submarine platform. The main structure is a large, long crescent-shaped reef whose convex side faces towards the south-east trades and the South Equatorial Current. The reef front of the main reef recurves inwards at both ends and is cut by two or three passes. The main reef has a very broad reef flat, extending up to several hundred metres across in parts. Together with much of the broad reef flat it is emergent at low tides. Apart from calcareous red algae it supports a few pocilloporoid corals. Down to at least depth the substrate is swept clear of attached biota, although on the sides of spurs or buttresses a few corals exist. Underwater photographs of some of the numerous knolls and banks behind the reef show that the density of