The biogeochemistry and trace metals distribution of mangrove rhizospheres

Abstract

Soils and porewater of the rhizosphere of mangrove trees, Rhizophora mangle L. and Avicennia schaueria Leech., of the salt marsh grass Spartina alterniflora Loisel, and of unvegetated mud flats, were analyzed salinity, platinum electrode redox potential, organic matter content, sulfide concentrations, and the total changeable concentrations of trace metals (Fe, Zn, Cu, Pb and Cd). The study was conducted in a fringe m forest in Sepetiba Bay, Rio de Janeiro, Brazil. The rhizospheres differed in their biogeochemistry. Mud f Rhizophora soils were very reducing, with highest concentrations of sulfide. Avicennia soils showed t variability of the variables measured, with the rhizosphere changing from oxic to anoxic conditions. Spa on the other hand, were generally oxic, with very low sulfide concentration. The distribution of trace metals in these soils varied with the major physical and chemical characteri flat soils presented the highest total trace metal concentrations followed by mangrove soils and Spartina soils. exchangeable trace metals were similar among the different soils with the exception of Avicennia soils, w their characteristic instability of redox conditions, presented much higher exchangeable trac