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Nitrogen retention in salt marsh systems across nutrient-enrichment, elevation, and precipitation regimes: a multiple stressor experiment
Citation:
Oczkowski, A., C. Wigand, Alana Hanson, E. Markham, K. Miller, AND Roxannel Johnson. Nitrogen retention in salt marsh systems across nutrient-enrichment, elevation, and precipitation regimes: a multiple stressor experiment. Estuaries and Coasts. Estuarine Research Federation, Port Republic, MD, 39(1):68-81, (2016).
Impact/Purpose:
Here we look at the impact of multiple co-occuring stressors on the New England salt marsh dominant plant, Spartina alterniflora. There is incrasing concern about how coastal salt marshes will respond to the impacts of climate change and fluctuating nutrient loads. While these impacts are often studied in parallel, here we look at the net impact of sea-level rise, nutrient enrichment, and altered precipitation associated with climate change on Spartina.
Description:
In the Northeastern U.S., multiple anthropogenic stressors, including changing nutrient loads, accelerated sea-level rise, and altered climactic 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 dominant 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 (normal, storm, and no precipitation) and three elevations (low, mean, and high). A quarter of the way into the experiment (1 month), an N stable isotope tracer was added to a portion of the rainfall received by the normal and storm treatments. At the completion of the experiment, Spartina in the normal treatments retained far more tracer than the treatments receiving the biweekly storms, with most tracer recovered at the highest level as high pot Spartina received direct tracer input to stems and sediment surface. When considering total N availability, the plants in the nutrient enriched treatments were estimated to take up far more N than the unenriched. Experimental results suggest that the timing and delivery of rainfall may be an important factor in how salt marshes intercept, retain, and transform N.
