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VARYING STABLE NITROGEN ISOTOPIC RATIOS OF DIFFERENT COASTAL MARSH PLANTS AND THEIR RELATIONSHIPS WITH WASTEWATER NITROGEN AND LAND USE IN NEW ENGLAND, USA
Citation:
WIGAND, C., R. A. MCKINNEY, M. L. COLE, G. B. THURSBY, AND J. CUMMINGS. VARYING STABLE NITROGEN ISOTOPIC RATIOS OF DIFFERENT COASTAL MARSH PLANTS AND THEIR RELATIONSHIPS WITH WASTEWATER NITROGEN AND LAND USE IN NEW ENGLAND, USA. ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 131(1-3):71-81, (2007).
Impact/Purpose:
to study the relationships of the stable nitrogen isotopic ratios of salt marsh plants
Description:
Stable nitrogen isotopic ratios of coastal biota have been used as indicators of sources of anthropogenic nitrogen. In this study the relationships of the stable nitrogen isotopic ratios of salt marsh plants, Iva frutescens (L.), Phragmites australis (Cav.) Trin ex Steud, Spartina patens (Ait.) Muhl, S. alterniflora Loisel, Ulva lactuca (L.), and Enteromorpha intestinalis (L.) with wastewater nitrogen and land development in New England are described. In the study, five of the six plant species (all but U. lactuca) showed significant relationships of increasing ¿15N values with increasing percent wastewater nitrogen. There was a significant (p < 0.0001) downward shift in the ¿15N of S. patens (6.0 ¿ 0.48 0) which is mycorrhizal compared with S. alterniflora (8.5 ¿ 0.41 0). The downward shift in ¿15N may be caused by the assimilation of fixed nitrogen in the mycorrhizal roots of S. patens. Stands of P. australis within sites had wide ranges of ¿15N values, evidently influenced by the type of shoreline development or vegetated buffer at the immediate upland border. In residential areas, the presence of a vegetated buffer (n = 24 locations) significantly (p < 0.001) reduced the ¿15N (mean = 7.4 ¿ 0.43 0) of the P. australis compared to stands where there was no buffer (mean = 10.9 ¿ 1.0 0; n = 15). Among the marsh plant species, I. frutescens located near the upland border showed the most significant (R2 = 0.64; p = 0.006) inverse relationship with the percent agricultural land in the watershed. In New England salt marshes, the ¿15N of P. australis and I. frustescens stands are apparently indicators of local, nitrogen inputs near the upland border, while the ¿15N of Spartina species on the marsh landscape relates with the integrated, watershed-sea nitrogen inputs.