LTREB: Porewater nutrient concentrations in control and fertilized plots in a Spartina alterniflora-dominated salt marsh, North Inlet, Georgetown, SC : 1993-2018

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. 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 began at
two locations in December 1993, and at three additional locations in
January 1994. Sampling occurred approximately monthly through 2018.
Sampling occured 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.