Effects of Sphagnum moss and urban runoff on bioavailability of lead and zinc from acidic wetlands of the New Jersey pinelands

The effects of Sphagnum and urban runoff on the bioavailability of metals were tested by adding PbCl2 and ZnCl2 to laboratory microcosms constructed of peat substrate with or without live Sphagnum spp. and planted with Acer rubrum L. seedlings or Vaccinium macrocarpon Ait. shoots. We hypothesized that Sphagnum would increase bioavailability through its acidifying action, while urban runoff would decrease availability through increases in alkalinity. Metals were more available to the test plants treated with acidic swampwater than with alkaline runoff. Sphagnum moss caused increases in tissue concentrations in V. macrocarpon, but not in A. rubrum. The latter species took up more metals when grown on substrate from sites receiving runoff, whereas the former took up more metals from substrate from undisturbed sites, despite the lower substrate metal concentrations. Differences in uptake by the two species may reflect differences in their ability to root in the Sphagnum mat. The results demonstrate that Sphagnum spp. exerts strong species-specific effects on the uptake of metals by vascular plants, and that plant species native to acidic wetlands vary widely in their response to metals in the substrate.