Hard Coral Assemblages on Seawalls in Singapore

— Singapore’s shores have been extensively modifi ed to meet the rising demands of economic and recreational activities, and seawalls are a resultant ubiquitous feature of the island state’s coastline. In spite of the harsh environmental conditions, seawalls in Singapore are known to harbour rich intertidal communities. This study surveyed the hard coral assemblages at zones immediately above and below the chart datum of seawalls at the southern offshore islands. Seventeen genera of hard corals were recorded. Zones below chart datum had greater diversity (14–15 genera; 17 colonies/m) than those above (10–14 genera; 7 colonies/m) and of the physical characteristics analysed, only depth infl uenced the distribution of coral communities on seawalls. With increasing deterioration of natural reefs and degradation to loose rubble, the results indicate that seawalls can provide a suitable substrate for the recruitment and growth of hermatypic corals. If appropriately designed, seawalls can assist in the recolonisation of corals and reef communities and function as cost-effective forms of artifi cial reefs.