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The importance of groundwater and other ecohydrological impacts in the management of salt marsh plant communities
Boorman, L.A.; Hazelden, J. (2005). The importance of groundwater and other ecohydrological impacts in the management of salt marsh plant communities, in: Herrier, J.-L. et al. (Ed.) Proceedings 'Dunes and Estuaries 2005': International Conference on nature restoration practices in European coastal habitats, Koksijde, Belgium 19-23 September 2005. VLIZ Special Publication, 19: pp. 335-343
In: Herrier, J.-L. et al. (Ed.) (2005). Proceedings 'Dunes and Estuaries 2005': International Conference on nature restoration practices in European coastal habitats, Koksijde, Belgium 19-23 September 2005. VLIZ Special Publication, 19. Vlaams Instituut voor de Zee (VLIZ): Oostende. XIV, 685 pp., more
In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more

Available in  Authors 
Document type: Conference paper

Keywords
    Ground water; Salt marshes; Marine
Author keywords
    Ecohydrology; Habitat creation

Authors  Top 
  • Boorman, L.A.
  • Hazelden, J.

Abstract
    Salt marshes are characterized by the presence of plants tolerant of some degree of salinity, although freshwater inputs can also be a significant component of the ecosystem. Sources and routes of freshwater can include river flow into the estuary, groundwater flow along a defined aquifer or channel and diffuse seepage as well as rainfall. In addition both fresh and saltwater flows can be the agents of transport to and from the marsh itself of sediment, mineral nutrients, pollutants and particulate and dissolved organic carbon. A common feature of many valley salt marshes is the presence of seepages of freshwater, particularly along the edge of the upper marsh, local upwelling or flow through permeable soil layers within the marsh. They can often be distinguished by the presence of plant species not fully tolerant of seawater. The commonest is Phragmites australis which can be seen as isolated clumps marking localized freshwater seepages or more widespread in areas where the soil salinity is reduced by a generalized freshwater input. While surface and groundwater flow can provide necessary plant nutrients excessive nutrient loading can result in hyper-eutrophic conditions with major effects on the biodiversity of the flora and fauna. Groundwater flows can cause the transport of these nutrients over considerable distances necessitating the use of special techniques to determine their source. This study also showed that excessive nutrient levels could be transported through to near-shore sediments with possible effects on marine habitats. Generally, however, salt marshes can be regarded as sinks which control the eutrophication of coastal waters by removing excessive nutrients. More is known about groundwater dynamics in wet coastal grasslands, enabling the prediction of changes. The installation of extensive instrumentation at specific sites has enabled the development of numerical models to study the groundwater dynamics of the forest-marsh interface. The next major step will be to integrate these various models in such a way that for any given salt marsh the underlying ecological processes can be understood sufficiently to develop management techniques. It has been demonstrated that current measures may be inadequate to restore fully the ecological processes of a healthy robust estuary or to reinstate the full beneficial functions of the estuarine ecosystem. This shows that the successful management of estuaries and coastal waters requires an ecohydrology-based catchment-wide approach. This will require a change in thinking and in management concepts for all estuaries and coastal waters.

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