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28b Overview from Ducks Unlimited, Inc.
Published in Donald A. Hammer, Constructed Wetlands for Wastewater Treatment, 2020
Another important benefit sewage effluent may provide is a stable water supply for wetlands in areas where the water resource is limited. This becomes extremely important in light of the fact we are losing approximately 185,500 ha of wetlands annually in the United States.6 Caution should be taken, however, in using this justification carte blanche for pumping effluent into natural wetlands. Indiscriminant exploitation of natural marshes can lead to their degradation.7 The addition of sewage effluent to a natural marsh may hasten eutrophication and increase exposure to toxic compounds or elements. We do not know the long-term effects on the density and diversity of the organisms in the ecosystem when it is put under these types of stresses. The design of a wastewater treatment marsh is site-specific. An evaluation of the effects of an effluent water supply on the receiving water body, and ultimately on waterfowl and other wildlife for which the system is designed to benefit, must be conducted and understood prior to constructing a facility.
Marshes: Salt and Brackish
Published in Yeqiao Wang, Wetlands and Habitats, 2020
Salt and brackish marshes are vegetated coastal habitats that occur along the edges of estuaries, defined as places where rivers meet oceans. These highly productive habitats are dominated by terrestrial vegetation rooted in sediment and exposed to daily tidal inundation. An example of a salt marsh plant community is shown in Figure 3.1. Coastal marshes are created when vegetation captures terrestrial sediments carried by rivers, thereby elevating the habitat above sea level. At high tide, a variety of estuarine animals, including crabs, snails, and fish, use the marsh for foraging and habitat protection. At low tide, terrestrial animals, including insects, birds, rodents, and even ungulates such as elk, are common visitors. Coastal marshes link marine and terrestrial ecosystems, making them unique and highly valuable.
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Published in Ali Dinar Abdullah, Modelling Approaches to Understand Salinity Variations in a Highly Dynamic Tidal River, 2017
Under natural conditions these wetlands once covered an area of approximately 15,000 to 20,000 km2, and have been recognized as the greatest wetland region in the Middle East and Western Eurasia (UNEP, 2001). The marshes are primarily fed by flows of the Tigris, Euphrates and Karkheh rivers, which fork into series of braided canals that discharge into the marshes. The average depth ranges from 1 to 1.5 m and reaches up to 6 m in some places. The wetlands and surrounding areas are characterized by an extremely flat and very fertile alluvial plain, allowing extensive wheat and rice cultivation. The marshlands are home to around 500,000 people, locally named Marsh Arabs, who are descendants of the Sumerians. Most of the marshes are covered by natural plants, often reeds and papyrus, and are the habitat of several animals and fish and bird species. Its geographical location permits a stopover for some birds while migrating between Siberia and Africa. As such, the Mesopotamian Marshlands used to be an ecosystem and natural heritage of local and international importance that supported numerous species of wildlife and aquatic biodiversity (UNEP, 2001).
Hydraulic management of coastal freshwater marsh to conciliate local water needs and fish passage
Published in Journal of Ecohydraulics, 2023
Leo Guiot, Ludovic Cassan, David Dorchies, Pierre Sagnes, Gilles Belaud
In many coastal areas, open marshes have been controlled for centuries to increase land-use for agriculture, pasture, and to contribute to flood prevention. This has led to the channelization of the marshes and flow control based on hydraulic structures, such as sluice gates and weirs to maintain water levels around targeted values, to regulate seawater inflows, and to control wetland drainage. In addition, specific hydraulic structures have been designed to operate automatically (thanks to the hydrostatic pressure) in response to the tide, to prevent salt intrusion and tidal flood issues (Giannico and Souder 2005). However, these coastal hydraulic structures create physical barriers and, sometimes, subsequent flow conditions which constrain fish passage: sluice gates impose large flow velocities by contracting the flow, tide gates are physical barriers at high tide (Doehring et al. 2011; Wright et al. 2014), while weirs create water falls (Amaral et al. 2016). Therefore, all these structures may have an effect on fish migration either by stopping individuals and preventing them from reaching suitable habitats to spawn or to grow, or by adding a delay in their migration time (Ovidio and Philippart 2002). This delay may result in fish arriving in these habitats under unfavourable environmental conditions. These ecological consequences participate in the decline of some fish populations or species, such as the European eel (Anguilla anguilla) (Feunteun 2002; Bult and Dekker 2007)
Quantifying blue carbon for the largest salt marsh in southern British Columbia: implications for regional coastal management
Published in Coastal Engineering Journal, 2021
Maija Gailis, Karen Elizabeth Kohfeld, Marlow G. Pellatt, Deborah Carlson
Previous studies have suggested that the quantification of a salt marsh’s blue carbon potential can be used to prioritize restoration efforts, as well as support management decisions that help communities adapt to climate change and mitigate greenhouse gas emissions (Duarte et al. 2013; Sheehan et al. 2019). For example, restoration efforts can be prioritized for areas that allow marsh migration into agricultural or rural areas near the coast, to increase salt marsh area, and reduce the threat of coastal squeeze (Elsey-Quirk et al. 2011; Temmerman et al. 2013; Schuerch et al. 2018). In areas where hard barriers cannot be removed, applying living shoreline management and restoration techniques can be used to enhance the resiliency of a marsh in the face of sea-level rise (Temmerman et al. 2013; Sheehan et al. 2019).
Identifying marsh dieback events from Landsat image series (1998–2018) with an Autoencoder in the NIWB estuary, South Carolina
Published in International Journal of Digital Earth, 2020
Huixuan Li, Cuizhen Wang, Jean T. Ellis, Yuxin Cui, Gwen Miller, James T. Morris
Salt marshes grow in the intertidal zone between land and sea and are dominated with salt-tolerant grasses, herbs, and low shrubs (Adam 1990). The significance of marsh habitat to natural and human environments has been widely recognized in aspects such as reducing shoreline erosion, filtering urban runoff and allowing for sediment deposition (Reed, de Luca, and Foote 1997), purifying coastal water from urbanization (Van Dolah et al. 2008; Rai 2008), mitigating storm impacts (Boutwell and Westra 2016; Narayan et al. 2017), carbon sequestration (Chmura et al. 2003; Drake et al. 2015), nourishing wildlife habitats and supporting seafood industry (Boesch and Turner 1984; Upchurch and Wenner 2008). Acute marsh dieback (AMD) has been sporadically observed on coasts where healthy salt marshes experienced browning and thinning of aboveground foliage, sometimes turning to rhizome stubble and eventually mudflat (Alber et al. 2008). It is also termed sudden vegetation dieback (SVD) since the affected marsh often died within 4–8 months (Elmer et al. 2013). The influence of marsh dieback to the abovementioned environmental, ecological and economic values could be tremendous.