The mechanism of sediment trapping in mangrove habitats isshown in Fig. 2 (Furukawa et al., 1997; Kathiresan, 2003a). Themangrove structures inhibit tidal flows, probably due to the frictionforce which the trees with their root system provide. The soil particlesare carried in suspension into mangrove forests from seawater by theincoming tide, and the soil particles are left behind in the swamps andwithin the root system by the outgoing tides. Thus, the particles settle inthe forests during the low tide, probably when the turbulence getsreduced and water velocity at low tide becomes sluggish and low tocarry the particles back to the sea (Fig. 4). It has been estimated byKathiresan (2003a) that mangroves help in trapping the sediment up to25 % at low tide as compared to high tide. This high efficiency oftrapping suspended sediment may be attributed to widespreadoccurrence of numerous respiratory roots in Avicennia and to compactlyarching stilt roots of Rhizophora. The density of mangrove species and
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