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Growing up to 15m tall, they have cream, grey to brown bark with slight vertical fissures, with no buttresses or prop roots. Their pneumatophores are cone-shaped (unlike the pencil-like ones of Avicennia). Leaves are rounded, leathery, opposite, with similar upper and undersides of the leaf. Flowers are white and pom-pom-like and open only for one night. Their fruits are large (4 cm) green, leathery berries with a star-shaped base containing 100-150 tiny seeds that are white, flattened and buoyant.
Sonneratia alba can tolerate wide fluctuations in salinity and often grow on exposed, soft but stable mudbanks low on the tidal mudflats along banks of tidal rivers, creeks and within sheltered bays of offshore islands and reef cays. It is believed that they store excess salt in old leaves which they later shed. They are able to survive inundation by salt water twice a day, and in "soil" which is unstable and poor in oxygen (anaerobic). They also have to deal with swollen rivers carrying silt during the wet season, as well as violent storms that hit the coasts.
They provide a variety of important ecosystem roles: a refuge and food for a variety of flora and fauna, a natural water filter, and an important stabilizer of coastal and river banks. Their roots prevents mud and sand from being washed away with the tide and river currents. Mangrove trees also slowly regenerate the soil by penetrating and aerating it (other creatures such as crabs and mud lobsters also help in). As the mud builds up and soil conditions improve, other plants can take root. Mangrove trees also reduce the damage from violent storms.