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.