The effect of increased sediment accretion on the and growth of Rhizophora apiculata seedlings

The effects of experimental sediment accretion on the survival and growth of Rhizophora apiculata seedlings planted on an expanding mud flat in Pak Phanang Bay (south-east Thailand) were assessed. Seedling mortality rates increased linearly (R² = 0.87, F=75.9, P<0.0001) with increasing sediment accretion, at a rate of 3% per cm of sediment deposited, and implied a 96% increase in mortality at the highest sediment accretion applied (32 cm). Similarly, seedling growth declined linearly with increasing sediment accretion (r= - 0.95, P<0.01) with the seedlings receiving 32 cm of sediment showing no significant growth. These results clearly show that Rhizophora apiculata seedlings will not be efficient colonizers of coastal areas exposed to sudden events of high (>4 cm) sediment accretion and, therefore, afforestation programmes based on this species are unlikely to be successful in such areas.