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

Pollution (cont)

Oil • Chemicals • Sewage and other enrichment • Litter

Oil

Oil is perhaps the most conspicuous contaminant which may affect a saltmarsh. This may be in the form of chronic pollution from discharges by estuary based oil industries or by occasional input from oil incidents occurring at sea. A review of major accidental oil spillages, including the "Torrey Canyon", during the 1960's and 1970's suggests that saltmarsh vegetation often recovers after a single oil spillage (Baker 1979). Chronic pollution, on the other hand, may cause long-term loss of saltmarsh vegetation and effects on individual marshes can be very different from one incident to another. This will depend on a number of factors, which include the fact that some plants are more tolerant to oil than others. In addition, the volatility of the oil itself is important, with the lighter fractions, which are lost most rapidly, being the most toxic.

The presence of oil deposits on a saltmarsh may suggest that its removal should be undertaken as a matter of urgency. Where the crude is heavy and easily picked up it may be possible to remove it mechanically but, as this may cause physical damage to the marsh, it is not recommended, except for the heaviest contamination near to or on the high water line. Evidence from studies in the eastern US suggest that use of chemical dispersants may also be more damaging than leaving the oil to degrade naturally. In general, all possible attempts should be made to prevent contamination in the first instance.