Evaluating sediment characteristics is essential, particularly as it pertains to salt marsh restoration dieback events. These dieback events on salt marshes result in the loss of Spartina alterniflora exposing open areas that create a loss in the accumulation of organic material and areas that become highly susceptible to erosion. Often an influential cause for vegetative dieback events are a result of prolonged water inundation. Vegetation exposed to continued water inundation promotes water logged soils as well as increased concentrations of sulfides in the soils porewater . Another potential association to a vegetative dieback event could be caused by soil desiccation. As a result, from reduced water inundation soil desiccation would stimulate an increased supply of toxic metals and lowers pH soil levels .
One of the most influential characteristics to the loss of tidal influences is the absence of reducing sulfidic conditions. Hydric soil formations are developed through anaerobic (i.e., anoxic) conditions, which results from prolonged hydroperiods of soils. These anaerobic environments make sulfide materials readily available for sulfur adaptive bacteria. Sulfur adaptive bacteria are able to transfer sulfate to sulfide (hydrogen sulfide; H2S) and pyrite (FeS2) . Often these processes are accelerated through an increased concentration of organic material. While sulfide soils do not cause an issue under natural tidal regimes, when these soils are left to dry, the sulfides in the soil begin to oxidize producing sulfuric acid and eventually jarosite, which greatly lowers a soils pH (<4.0) . These processes create elevated acidic conditions that could negatively impact nearby vegetation and aquatic organisms.
Under natural tidal salt marsh conditions, it is expected that the sequestration of carbon, nitrogen, and phosphorus would increase due to the reduced rate of decomposition. Carbon, nitrogen, and phosphorus in soils are the primary component needed for plant growth.
Carbon (C) accumulation within salt marshes is the base layer for the incorporation and retention of nutrients and plant biomass. Contributions of organic and inorganic sediments eventually build up the marshes peat layer. Organic substrates and fine-textured materials (i.e., silt, loam, clay) tend to retain moisture and are more suitable for plant growth in salt marsh environments.
Nitrogen (N) is an essential nutrient needed by plants. Nitrogen is found throughout a plants physiology and contained within their cells, and proteins. Nitrogen can enter soils through numerous pathways and become incorporated into the plant. However, when nitrogen is incorporated into hydric soil it is converted in the mineral form of nitrate, which can then become utilized by plants. Changes to nutrient availability within salt marsh ecosystems can drastically alter the species composition. Most of the species will transition into a macroalgae community with excess nitrogen availability . Spartina alternifora has also been shown to outcompete Spartina patens within excess nitrogen sources .
Phosphorus (P) is also an essential nutrient that helps transfer energy from sunlight to the plant. Phosphorus is the general nutrient that helps simulate early root development, and strengthens stalks and stems.
These compounds are the major nutrients that are needed towards the incorporation of peat material and influence a healthy salt marsh through sequestration. As oxidization occurs within restored salt marshes it is expected that these areas would experience a loss organic matter due to an increase of decomposition. The presence of inorganic material used as placement material potentially hinders new materials becoming incorporated into soils . Although nutrients can be beneficial for the revitalization of plant growth, excess nutrients may also result in a decline of the recovery of the marsh.
Healthy salt marshes are considered a sink for trace metal. These metals are often tied up in organic matter and sulfides that result from an anaerobic and extended flooding. Tidal restrictions to presently restored placement areas would cause oxidized conditions of total organics and sulfides. Oxidized soils would subsequently solubilize metals into soil and vegetative porewater. Oxidized environments could then become sources for solubilized metals through the exchange of porewater and surface water. Acidic soils could also further increase the solubility of metals within these environments.
 Anisfeld, S.C., M.J. Tobin and G. Benoit. 1999. “Sedimentation Rates in Flow-Restricted and Restored Salt Marshes in Long Island Sound.” Estuaries 22:231-44
 Ogburn, Matthew Bryan, and Merryl Abler. “An investigation of salt marsh dieback in Georgia using field transplants.” Estuaries and Coasts 29.1 (2006): 54-62
 Rabenhorst, M.C., D.S. Fanning, and S.N. Burch 2002. Acid Sulfate Soils, Formation. In: R. Lal (ed.). Encyclopedia of Soil Science. Marcel Dekker, New York. 14-18.
 Reddy, K.R., and R.D. DeLaune. 2008. Biogeochemistry of Wetlands: Science and Applications. CRC Press, Taylor & Francis Group, Boca Raton, FL.
 Wigand, C., R. McKinney, M. Chintala, M. Charpentier, and G. Thursby. 2003. “Relationships of Nitrogen Loadings, Residential Development and Physical Characteristics with Plant Structure in New England Salt Marshes.” Estuaries 26: 1494-1504.