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Marine Ecology Progress Series

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MEPS 433:43-52 (2011)  -  DOI:

Nitrogen uptake by the shoots of smooth cordgrass Spartina alterniflora

T. J. Mozdzer1,3,*, M. Kirwan1,2, K. J. McGlathery1, J. C. Zieman1

1Department of Environmental Sciences, University of Virginia, 291 McCormick Rd, Charlottesville, Virginia 22904, USA
2Patuxent Wildlife Research Center, US Geological Survey, 12100 Beech Forest Rd, Laurel, Maryland 20708, USA
3Present address: Smithsonian Environmental Research Center, 647 Contees Wharf Rd, Edgewater, Maryland 21037, USA

ABSTRACT: The smooth cordgrass Spartina alterniflora is the foundation species in intertidal salt marshes of the North American Atlantic coast. Depending on its elevation within the marsh, S. alterniflora may be submerged for several hours per day. Previous ecosystem-level studies have demonstrated that S. alterniflora marshes are a net sink for nitrogen (N), and that removal of N from flooding tidal water can provide enough N to support the aboveground biomass. However, studies have not specifically investigated whether S. alterniflora plants assimilate nutrients through their aboveground tissue. We determined in situ foliar and stem N uptake kinetics for 15NH4, 15NO3, and  15N-glycine by artificially flooding plants in a mid-Atlantic salt marsh. To determine the ecological importance of shoot uptake, a model was created to estimate the time of inundation of S. alterniflora in 20 cm height intervals during the growing season. Estimates of inundation time, shoot mass, N uptake rates, and N availability from long-term data sets were used to model seasonal shoot N uptake. Rates of aboveground N uptake rates (leaves + stems) were ranked as follows: NH4+ > glycine > NO3. Our model suggests that shoot N uptake may satisfy up to 15% of the growing season N demand in mid-Atlantic salt marshes, with variation depending on plant elevation and water column N availability. However, in eutrophic estuaries, our model indicates the potential of the plant canopy as a nutrient filter, with shoot uptake contributing 66 to 100% of plant N demand.

KEY WORDS: Foliar uptake · Stem uptake · Ammonia · Glycine · Nitrate · DON

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Cite this article as: Mozdzer TJ, Kirwan M, McGlathery KJ, Zieman JC (2011) Nitrogen uptake by the shoots of smooth cordgrass Spartina alterniflora. Mar Ecol Prog Ser 433:43-52.

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