Accumulation of heavy metals by Spartina alterniflora, the dominant vegetation in many salt marshes, is a concern for habitat restoration. We hypothesized that metal concentrations would vary between tissue types of Spartina and would be significant in salts excreted on the leaf surface. Spartina was cultivated at a constant salinity in two types of sediment (natural marsh material and dredge material) with three levels of metal additions (Cd, Cr, Cu, Ni, Pb and Zn). In a concurrent experiment, salinity treatments (overlying water at 0 psu, 15 psu and 30 psu) were applied to Spartina grown in a single combination of sediment type and metal level. Sediment type, sediment metal concentration and the salinity of overlying water all affect the distribution of metals in tissues of Spartina as well as the excretion of metals in salts. Concentrations of Ni and Zn in all tissues of Spartina varied as a result of interactions between sediment type and metal additions. Of these two metals, only Zn varied significantly in excreted salts. Cadmium distribution in aboveground tissues varied with both sediment type and metal addition. Variations of Zn and Cd in excreted salts were related to metal addition and salinity treatments. Lead concentrations in the excreted salts decreased as the salinity of the overlying water increased. The distribution of Cu between photosynthetic tissue (leaf) and structural tissue (stem) varied between salinity treatments. The presence of metals in Spartina tissues that are commonly grazed as well as in excreted salts on the leaf surface makes these metals potentially available for trophic transfer to many organisms that rely on this plant and its associated detritus as a food resource.
