found that the concentrations of As in fungi and algae growing on mangrove roots were much higher than those of flora and fauna in the mangrove ecosystem. Mangrove plant could release some low molecular weight organic acids (e.g. malate, citrate, and oxalate), which were responsible for increasing bioavailability of metals in sediments near the rhizosphere ( Jones et al., 1996 and Lu and Yan, 2007). These interactions of sediment and mangrove plant will influence the distribution of As in sediment from different regions.