Nitrogen and phosphorus concentrations within North Inlet, South Carolina—Speculation as to sources and sinks

191

Extensive measurements of material concentrahons and water velocities at a transect across North Inlet, South C a r o h a (USA) allowed the estimation of net material and water fluxes. Sampling periods were distnbuted seasonally and according to tidal height. Statistical and hydrodynanlic models were used to develop flux estimates for specific tidal cycles. There was a net discharge of water from the marsh-estuanne system to the Atlantic Ocean which is attributed to rainfall runoff and freshwater input from an adjacent estuary. All constitutents were exported seasonally and annually from the system -except total semments, imported during fall and winter, and chlorophyll a and zooplankton, imported in summer and fall. ATP, bird biomass and macrodetritus were exported throughout the year. Export of carbon, nitrogen and phosphorus from North Inlet is high compared to other systems studied to date. Large net fluxes of DOC during winter imply coupling with the uplands. The high rates of export of ammonium and orthophosphate along with detritus and microorganisms suggest major decomposition processes are taking place within the system. Export of ammonium and orthophosphate to the coastal ocean also suggest a feedback loop with phytoplankton utilizing these materials, then in turn phytoplankton are imported into the estuary where they are consumed and remineralized. Previous explanations of outwehng and tidal transport are examined and found to be individually lacking. It is proposed that any comprehensive explanahon of the magnitude and direction of transport must include a physical explanation of water motion and the biological and physical mechanisms by which materials are added or removed from tidal waters. A comprehensive explanation of outwelling in North Inlet IS proposed which describes this system as an ebb-dominated, bar-built estuary with good flow connection to the sea and with some freshwater input. It is also a fertile system with high productivity providing materials for export to the coastal ocean and utilization of other imported materials.

Section: Nitrogen Fluxesmentioning

confidence: 99%

Section: Phosphorus Fluxmentioning

confidence: 99%

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The outwelling hypothesis and North Inlet, South Carolina

Dame¹,

Chrzanowski²,

Bildstein³

et al. 1986

191

“…Flume studies in Atlantic Coast marshes have demonstrated that salt marsh ecosystems are predominantly a net sink for NH 4 + , NO 3 -, and NO 2 - (Wolaver 1981, Wolaver & Zieman 1984, Wolaver et al 1984, Whiting et al 1989, Childers et al 1993, and that they can also be a source (Wolaver et al 1984, Childers et al 1993 or sink (Wolaver & Zieman 1984, Childers et al 1993) of dissolved organic nitrogen (DON). Wolaver & Zieman (1984) showed that N removal from flooding tides could supply up to 100% of the N needed to support the biomass in tall-form Spartina alterniflora and 30 to 105% of the N needed for intermediate-form S. alterniflora in a Virginia (USA) salt marsh; however, the contribution of shoot uptake to removal was not investigated.…”

Section: Introductionmentioning

confidence: 99%

Nitrogen uptake by the shoots of smooth cordgrass Spartina alterniflora

Mozdzer

Kirwan²,

McGlathery³

et al. 2011

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

“…These marshes contain a variety of subsystems (oyster reefs, mussel beds, high and low marsh vegetation, marsh and subtidal sediments) each of which may act as a source or a sink for SRP during tidal exchange (Keunzler 1961, Gardner 1975, Wolaver et al 1983, Dame et al 1989. The relative contribution of each of these subsystems to the net tidal exchange of SRP from the marsh, however, is not fully understood (Nixon 1980, Wolaver et al 1984.…”

Section: Introductionmentioning

confidence: 99%

Foliar release of soluble reactive phosphorus from Spartina alterniflora in a Georgia (USA) salt marsh

Pakulski¹

1992

Foliar release of soluble reactive phosphorus (SRP) from live shoots of Spartina alterniflora (Loisel.) was investigated in a Georgia (USA) salt marsh. Average foliar SRP release rates varied from ~t h values from individual plants as high as 61.7 pg P (g dry undetectable to 7.5 pg P (g dry wt)-' h-' Wwt)-' h-'. Release rates of SRP generally exhibited little die1 variation and were highest in midsummer. Estimates of extrafoliar SRP accumulated on leaf surfaces varied from < 1 to 41 pg P (g dry wt leaf)-' and 0.8 to 1.7 mg P m-2 normalized to marsh area. Time course experiments revealed that SRP release was a 2-step process with a rapid solubillzation of extrafoliar SRP and a constant release thereafter. Releases of SRP from creekbank stands of S. alterniflora during tldal submergence were estimated to be 3.1 to 8.2 mg P m-2 d-l, with annual releases of 1.7 g P m-2 yr-l Foliar releases of SRP from the live plants are equivalent to 60 % of the annual production of particulate phosphorus as S. alterniflora detritus reported from Georgia salt marshes.