Influences of the macrophyte (Scirpus mariqueter) on phosphorous geochemical properties in the intertidal marsh of the Yangtze Estuary

The role of the marsh plant (Scirpus mariqueter) in phosphorus (P) biogeochemical cycling was investigated in the present study. The marsh plant had a significant influence on P adsorption, benthic fluxes and P speciation in the intertidal system. The adsorption capacities of P were significantly higher in the rhizosphere sediments (54.38-77.12 mg kg^-1) than in the bare sediments (43.91-54.81 mg kg^-1). Lower half saturation concentration constants also appeared in the rhizosphere sediments. Similar adsorption kinetic patterns were found for the bare and vegetated habitats, which showed an initial fast P adsorption reaction, followed by a slow adsorption process. However, compared with the unvegetated sediments, the relatively higher adsorption rate appeared in the rhizosphere sediments during the fast adsorption stage. Also, soluble inorganic P was effluxed into the overlying water in the unvegetated habitat. In contrast, soluble inorganic P was transported from the overlying water into the vegetated sediments during the growth season of S. mariqueter. The comparative analysis of P speciation in both bare and vegetated habitats revealed that S. mariqueter could enhance the accumulation of Fe-bound P, authigenic P and organic P in the rhizosphere sediments. The important role of S. mariqueter in P removal and storage has significant implications for the conservation and management of the Yangtze estuarine and intertidal marsh.