Freshwater marsh

Neubauer, S.C., and Anderson, I.C. (2003) Transport of dissolved inorganic carbon from a tidal freshwater marsh to the York River estuary. Limnol. Oceanogr. 48, 299-307. 

Barlocher, F. Biddiscombe, N. R. (1996). Geratology and decomposition of Typha latifolia and Lythrum salicaria in a freshwater marsh. Archiv fur Hydrobiologie, 136, 309-25. 

Merrill, J. Z. (1999). Tidal freshwater marshes as nutrient sinks Particulate nutrient burial and denitrification. Doctoral dissertation. University of Maryland, College Park, Maryland, USA. 

The porosity of the canopy is therefore n = 1- (n/4)ad. Using stem densities and diameters reported for the short- and tail-form of S. alterniflora [627], ad = 0(0.001)-0(0.01). In these marsh canopies the solid volume fraction ( ad) is sufficiently small to make the porosity effectively 1. However, in some freshwater marshes the solid volume fraction can be as high as 15%, corresponding to ad 0.2, and np = 0.8 (Fox et al., 2002 [196]). In mangrove swamps the solid volume fraction can be as high as 45%, np = 0.55, within the root zone [401],... 

There is little information on the presence of anaerobic FeOB in the rhizosphere. A preliminary survey of a Maryland tidal freshwater marsh soil indicated that nitrate-reducing anaerobic FeOB were present, albeit in low numbers ( 10 to 10 cells niL i Emerson, unpublished data). In freshwater sediments, Straub and Buchholz-Cleven (1998) found greater numbers of anaerobic nitrate-reducing FeOB (1 X 10 to 5 X 10 cells g ) than anaerobic phototrophic FeOB (0.1 to 3.9 X 10 cells g ). 

Tidal freshwater marshes are typically found upstream of estuaries. Water levels in these ecosystems are influenced by tides. These marshes are characterized by emergent macrophytes that are not tolerant to salinity. Vegetation diversity is typically high, with common species including cattails, pickerel weed, wild rice, arrowhead, and others. 

There are two types of marsh soils freshwater marsh soils and saltwater marsh soils. These soils are generally permanently waterlogged. Freshwater marshes occur in the areas adjacent to lakes and streams, whereas saltwater marshes occur in estuaries. Typical characteristics of these soils are... 

Results, University of Florida), (b) Relationship between methane concentration in soils and methane emissions from freshwater marsh (Ding et ah, 2005). 

In intertidal marsh soils, total inorganic phosphorus accounted for 14-40% of total phosphorus in freshwater marsh and 33-85% of total phosphorus in salt marshes. Inorganic phosphorus associated with Fe was most abundant in snrface sediments of both freshwater and brackish marshes, whereas Ca-bonnd P dominated inorganic phosphorus in salt marshes (Paludan and Morris, 1999). 

Approximately 90% of the methane transport from soils to the atmosphere in rice paddies and freshwater marshes is through aerenchyma portion of roots and stems of the plants. Gases are transported according to their concentration gradient, not only for CH4 but also for N2O (Yu et al.,... 

The emissions of NjO from adjoining salt, brackish, and freshwater marshes within the Louisiana Barataria basin are 31, 48, and 55 mg N m, respectively (Smith et al., 1983). The NjO flux from this study was similar to NjO from the Narragansett Bay sediment (Seitzinger et al., 1980). The addition of nitrate to the salt marsh significantly increased the rate of N2O emission (Smith et al.,... 

This case study demonstrated that freshwater diversion projects such as Caernarvon serve an important role in the reintroduction of freshwater and limited amount of mineral sediment necessary for promoting growth of marsh vegetation (the source of organic matter in marsh soil) in subsiding delta environments. In addition to sediment input, an important influence of the diversion on enhancing marsh stability is associated with the lowering of salinity, which reduces the sediment requirement for marsh maintenance (freshwater marshes have lower mineral sediment requirement than saline marshes). 

The role of these marshes as a major carbon sink has been determined from the carbon content of the sediment, vertical accretion rates, and the bulk density of the sediment (Smith et al, 1983b). Accretion rates were calculated from depth in sediment of the horizon for 1963, the year of peak Cs fallout (DeLaune et al., 1978). Net carbon accumulation was essentially the same in all three marshes 183, 296, and 224 g C m year from the saltwater, brackish, and freshwater marshes, respectively. A large percentage of hxed carbon, immobilized in accretionary processes, remained on the marshes (Table 18.4). Hatton et al. (1983) found similar carbon accumulation rates in these marshes. 

FIGURE 18.22 Changes in NOj-N concentrations between inlet and outlet of the ponded freshwater marsh receiving diverted Mississippi River water during periods of high pulse and medium pulse events. (Modified from DeLaune et al., 2005.)... 

Capacity of Freshwater Marsh to Process Nitrate IN Diverted Mississippi River Water... 

Denitrification was shown to be a major process in removing nitrate in diverted river water (Yu et al 2006). The capacity of freshwater marsh to remove all nitrate in the diverted river water was strongly influenced by the flow or discharge rate (DeLaune et al 2005). The ponded wetland did not completely remove the nitrate in river water at high flow or discharge (>100 m s ). On the basis of mass balance calculation using concentration difference between inlet and outlet, the system removed the nitrate-N at the rate of approximately 60 mg N m day or approximately... 

The amounts and profile distribution of various sulfur forms in Louisiana coastal marshes are important in understanding sulfur cycling as related to the origin and type of tidal wetland marshes. Sulfur forms and distribution were determined in P. hemitomon freshwater marsh, a S. patens brackish marsh, and a S. alterniflora salt marsh along a salinity gradient in Barataria Basin, Louisiana. Soil samples were fractionated into acid volatile sulfur (AVS), elemental sulfur, HCl-soluble sulfur, pyrite sulfur, ester sulfate sulfur, carbon-bonded sulfur, and total sulfur (see Chapter 11 for details). 

Seasonal field sulfur emission measurements (DeLaune et al., 2002b) were determined in a Spar-tina alterniflora salt marsh (10-12 ppt salinity), a Spartina patens brackish marsh (5-8 ppt), and a Sagittaria lancifolia freshwater marsh (0 ppt salinity), along a salinity gradient extending inland from the coast in the Mississippi River deltaic plain region of the coastal Lonisiana. Results... 

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