The Republic of Singapore consists of a main island and over 60 small offshore islands with fringing and patch reefs. It has a combined land area of approximately 660 km², and territorial waters cover 630 km². The human population of 3.9 million gives a high density of 5,900 persons per km² (Anon., 2000). The marine environment is an important resource contributing to economic growth. It supports one of the world's busiest ports and one of the largest oil refining centers. Close to 60% of the total coral reef areas have been lost through foreshore reclamation (Chou, 1995; Chou and Goh, 1998).

In Singapore's highly urbanised society, fishing and collecting from reefs and other coastal areas, either for the aquarium trade or for subsistence, declined steadily since the 1980s. Illegal collection of corals and other reef invertebrates stopped with stronger enforcement by the Police Coast Guard and a more informed public. The first, and so far only, arrest of coral smugglers was made in Oct 1991 (Anon., 1991). Effective regulatory measures prevent marine pollution. The greatest impact however, is the high sediment load generated by land reclamation, the regular dredging of rivers and shipping lanes, and the dumping of these materials out at sea.

Results of the monitoring programme since 1987 show live coral cover declining with both increasing depth and over time (Table 1). Corals generally do not occur beyond the 6m depth due to the high sediment load. While coral diversity and cover in most localities declined steadily, some localities, such as Lazarus Island (site L4) and Cyrene Reefs (site C1 and C2), suffered close to 100% loss in coral cover. This is attributed to their proximity to sedimentation-generating activities such as dumping of dredged spoils and reclamation respectively.

The coral reefs continue to suffer from the impact of sedimentation. A renewed survey program was initiated recently and data for 2 of the 10 permanent reef sites being monitored indicated an extension of the trend of steady, but small decline in live coral cover. A mass spawning event was confirmed in April this year, and further observations are being prepared for October to determine if mass spawning coincided with the inter-monsoon period. Many coral recruits were recently discovered on coral rubble covered by calcareous algae and a project is currently planned to examine the potential of exploiting this phenomenon for coral culture and reef rehabilitation.

Despite the small coral reef area in Singapore, hard coral diversity is relatively high, with almost 200 species recorded. Reef status in 2004 is mixed with reefs close to shore and adjacent to high coastal development and land reclamation showing clear degradation, with deeper parts of the reefs almost completely buried under sediments. Reefs further from shore and provided with the protection from nearby military bases, have shown improvement in live coral cover on the shallow reef areas.