Metal dynamics of plant litter of Spartina alterniflora and Phragmites australis in Metal-Contaminated salt marshes. Part 1: Patterns of decomposition and metal uptake

Authors

  • Lisamarie Windham,

    1. Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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  • Judith S. Weis,

    1. Department of Biological Sciences, Rutgers University, Newark, New Jersey 07102, USA
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  • Peddrick Weis

    Corresponding author
    1. Department of Radiology/G-621, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, New Jersey 07101–1709, USA
    • Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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Abstract

To investigate the decay rate and metal uptake in litter from two species of wetland plants, leaves and stems of senescent Spartina alterniflora and Phragmites australis (P) were obtained from the Hackensack Meadowlands (NJ, USA) in October 1998, and their initial metal contents were determined. Two types of S. alterniflora were obtained, one set from a natural site (NS) and one from a restored site (RS). Leaves and stems were placed in separate litterbags, and samples of each type were reciprocally transplanted into each of the three collection sites (NS, RS, and P) as well as in the laboratory, where they were alternately dried and wetted. Litterbags were retrieved from the field at four six-month intervals and after one year from the laboratory. Annual decay coefficients were greater for leaves than for stems. Stems of P. australis initially decomposed more slowly (37–63% remaining) than those of S. alterniflora (23–53 % remaining), but after two years, decay was comparable (8–40% remaining for both species). Decomposition was slower at the RS site than at the other field sites, and it was slowest in the laboratory. Metal concentrations initially were lower in stems than in leaves, and Cr, Pb, and Zn were lower in P. australis than in S. alterniflora. In the field, large increases (10- to 100-fold) in metal concentrations rapidly obliterated any initial differences between plant species. Metal concentrations in leaves rose more quickly and remained greater than in stems. For example, Cu approached 300 μg/g in leaves but was less than 200 μg/g in stems. In contrast to the modest rise in metal concentrations in the leaf tissue at the more contaminated RS site (Zn rose to ∼200 μg/g in sediments containing ∼400 μg/g), Cu and Zn concentrations in leaf litter at the P and NS sites increased to levels exceeding those in the surrounding sediment (Zn rose to ∼500 μg/g in sediments containing ∼200 μg/g). Temporal changes in metal pools (grams of metal per litterbag) were not discernable because of the negative correlation of mass remaining and metal concentrations as well as because of the great variability of metal concentrations within each treatment. Decomposition and the accumulation of metals may be influenced more by differences between tissue types than by species or sediment metal concentrations.

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