US EPA

3549116 

Journal Article 

Nitrogen Retention in Salt Marsh Systems Across Nutrient-Enrichment, Elevation, and Precipitation Regimes: a Multiple-Stressor Experiment 

Oczkowski, A; Wigand, C; Hanson, A; Markham, E; Miller, KM; Johnson, R 

2016 

1 

Estuaries and Coasts
ISSN: 1559-2723
EISSN: 1559-2731 

39 

1 

68-81 

10.1007/s12237-015-9975-x 

WOS:000367525900006 

In the Northeastern USA, multiple anthropogenic stressors,
including changing nutrient loads, accelerated sea level rise, and altered climatic patterns, are
co-occurring and are likely to influence salt marsh nitrogen (N) dynamics. We conducted a
multiple-stressor mesocosm experiment to assess impacts of climate change and nutrient load on N
uptake by the ecosystem dominant species. The New England salt marsh plant Spartina alterniflora
was planted at mean high water (MHW) and 15 cm above and below MHW in tanks plumbed to mimic
tides. The experiment consisted of two nutrient treatments (enriched, unenriched), three
precipitation treatments (rain, storm, and no precipitation or control), and three elevations
(low, mean, and high), with four replicate pots for each. A quarter of the way into the
experiment (1 month), an N stable isotope tracer was added to a portion of the precipitation
events received by the rain and storm treatments to assess how N is retained by the different
components of each treatment. At the completion of the experiment, Spartina pots in the rain
treatments retained far more tracer than the pots receiving the twice monthly storms, with the
most tracer recovered at the highest elevation in all precipitation treatments as these pots
received direct tracer input to stems and sediment surface. Experimental results suggest that the
elevation of the marsh as well as the timing and delivery of rainfall may be important factors in
how salt marshes intercept, retain, and transform N. 

Salt marsh; Tracer; Spartina alterniflora; Climate change; Precipitation; Stable nitrogen isotope; Experiment