Grazing • Access and amenity • Pollution • Coastal defence maintenance • Alternative uses

Pollution

Saltmarshes are often exposed to a variety of pollutants, which may be derived from agricultural production on adjacent land or the contamination of water courses and sediments by industry (heavy metals), sewage disposal, landfill leachate, oil and litter that is transported into the system. All these forms of pollution are likely to have some impact on the saltmarsh, although there is insufficient information available to determine if they are a major threat to the ecological integrity of these systems. In general, saltmarshes are thought to be significant sinks for pollutants, which may be incorporated into the marsh through the sediments that accumulate or taken up directly by saltmarsh plants.

Most of the studies upon which the above information is based are at least 10 years old and from the USA. Further work undertaken at Imperial College, London shows that there are elevated levels of heavy metals in Essex saltmarsh sediments (demonstrating the locking-up of pollutants) and that there is some accumulation in the vegetation (Meakins et al,, 1995 and Fletcher et al., 1995). However, this is not considered to be the primary cause of saltmarsh degeneration, although localised effects may be seen at outfalls where “shock loadings” of pollutants (and potentially their associated de-flocculants) exist (Leggett et al., 1995).

The main sources of pollution include:

Oil • Chemicals • Sewage and other enrichment • Litter