LTREB: Porewater nutrient concentrations and above-ground plant growth in control and fertilized plots, at a Spartina alterniflora salt marsh in North Inlet, Georgetown, SC: 1993-2016.

Morris J. T. and K. L. Sundberg (2017)

Porewater nutrient concentrations were measured as a component of a long-term project seeking to understand how salt marsh primary production and sediment chemistry respond to anthropogenic (e.g. eutrophication) and natural (e.g. sea-level rise) environmental change. Feedbacks between plants, sediments, nutrients and flooding were investigated with particular attention to mechanisms that keep marshes in equilibrium with sea level. Other data collected as part of the project include aboveground macrophyte biomass, plant density, marsh surface elevation and annual above ground primary productivity. These data have been used to develop the Marsh Equilibrium Model, an important tool for coastal resource managers. Sampling occurred at Spartina alterniflora-dominated salt marsh sites in North Inlet, a relatively pristine estuary near Georgetown, SC on the SE coast of the United States.

4D renderings of the harmonics of porewater ammonium, phosphate and sulfide concentrations, and above-ground plant growth at a Spartina alterniflora salt marsh in North Inlet, SC.  The individual spikes are annual cycles; monthly plant growth is color coded.  The change in tidal amplitude on the SC coast due to the lunar nodal cycle is about 4 cm (independent of MSL and SLR) over 18.6 years.  When the elevation of the marsh is super-optimal for plant growth, S. alterniflora productivity increases with greater tidal amplitudes.

North Inlet is a tidally-dominated, bar-built estuary, with a semi-diurnal mixed tide and a tidal range of 1.4m. The 25-km2 estuary is comprised of about 20.5 km2 of intertidal salt marsh and mudflats, and 4.5 km2 of open water. Sampling of pore water nutrients began at two locations in December 1993, and at three additional locations in January 1994. Sampling occurred approximately monthly through 2016. Sampling occurred at a sixth location from 2006 to 2010. The site was a dieback site that had recovered by 2010. At the other sites, the study is on-going. Porewater was collected at multiple depths from diffusion samplers and was analyzed for sulfide, chloride, ammonium, phosphate, and iron concentrations. There are five sampling locations at three sites. Two locations are in the low marsh; three locations are in the high marsh. One high marsh location had control sampling plots in addition to plots fertilized with nitrogen and phosphorus.  

Recommended citation for this data package

Morris J. T., K. L. Sundberg. 2017. LTREB: Porewater nutrient concentrations in control and fertilized plots in a Spartina alterniflora-dominated salt marsh, North Inlet, Georgetown, SC : 1993-2016. Environmental Data Initiative.

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