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(P266) Patterns of decomposition and metal uptake of plant litter of Spartina alterniflora and Phragmites australis in an urban estuary.
Windham, Lisamarie1, Weis, Judith2, Weis, Peddrick*,3, 1 Dept. of Earth & Environmental Sciences, Lehigh University, Bethlehem, PA, USA2 Dept. of Biological Sciences, Rutgers University, Newark, NJ, USA3 Dept. of Radiology, UMDNJ - N. J. Medical School, Newark, NJ, USA
ABSTRACT- We have been studying how metals move through urban estuarine food webs, particularly at the detrital base of the food web. Leaves and stems of senescent Spartina alterniflora , one set from a natural site (NS) and one from a site that had been restored a decade earlier (RS), and Phragmites australis (P) were obtained from the Hackensack Meadowlands in NJ in October and their metal contents determined. Leaves and stems of each type were reciprocally transplanted in separate litterbags into each of the three collection sites (NS, RS, and P) as well as in the laboratory. Litterbags were retrieved after four six-month intervals (one year in the laboratory). Annual decay coefficients were greater for leaves than stems. P. australis stems initially decomposed slower than S. alterniflora stems, but after two years decay rates were comparable. Decomposition was slower at the RS site than at the other field sites and was slowest in the laboratory. Metals were initially lower in stems than leaves, and Cr, Pb, and Zn were lower in P. australis than in S. alterniflora. In the field, large increases (10-100 fold) in metal concentrations rapidly obliterated any initial differences between plant species. Metal concentrations of leaves rose more quickly and remained greater than stems. In contrast to the modest rise in metal concentrations in the leaf tissue at the more contaminated RS site, litterbags at the P and NS sites increased in Cu and Zn concentrations to levels exceeding the surrounding sediment. Changes in metal pools over time were not discernable due to the negative correlation of mass remaining and metal concentrations and to the great variability of metal concentrations within each treatment. Decomposition and metal accumulation may be influenced more by differences between tissue types than by species or by sediment metal concentrations.
Key words: metals, detritus, urban estuary, litterbags
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