Contamination of coastal amenity areas is a common feature of many oil spills, leading to interference with recreational activities such as bathing, boating, angling and diving. Hotel and restaurant owners and others who gain their livelihood from the tourist trade can also suffer temporary losses. A return to normal requires an effective clean up programme and the restoration of public confidence.
Industries that rely on seawater for their normal operation can also be adversely affected by oil spills. Power stations and desalination plants which draw large quantities of seawater can be particularly at risk, especially if their water intakes are located close to the sea surface, thereby increasing the possibility of drawing in floating oil. The normal operations of other coastal industries, such as shipyards, ports and harbours, can also be disrupted by oil spills and clean-up operations.
Fisheries and Mariculture
An oil spill can directly damage the boats and gear used for catching or cultivating marine species. Floating equipment and fixed traps extending above the sea surface are more likely to become contaminated by floating oil, whereas submerged nets, pots, lines and bottom trawls are usually well protected provided they are not lifted through an oily sea surface. However, they may sometimes be affected by dispersed or sunken oil. Less common is mortality of stock, which can be caused by physical contamination or close contact with freshly spilled oil in shallow waters with poor water exchange.
A common cause of economic loss to fishermen is interruption to their activities by the presence of oil or the performance of clean-up operations. Sometimes this results from a precautionary ban on the catching and sale of fish and shellfish from the area, both to maintain market confidence and to protect fishing gear and catches from contamination. Cultivated stocks are more at risk from an oil spill: natural avoidance mechanisms may be prevented in the case of captive species, and the oiling of cultivation equipment may provide a source for prolonged input of oil components and contamination of the organisms. Cultured seaweed and shellfish are particularly vulnerable in tidal areas where they may become contaminated with oil as the tide drops.
It is almost always necessary to make a thorough investigation of the status of a fishery and alleged effects of a spill, in order to determine the real impacts. This will often require scientifically rigorous sampling and analytical techniques which are capable of documenting the damage and providing proof that any damage observed has been caused by the oil in question. Nevertheless, separating spill effects from other factors which affect fisheries is frequently problematic. Wild stocks of commercial species are in decline in many parts of the world because of over-fishing, industrial pollution, destruction of coastal habitats and other natural factors such as increasing sea temperature. Similarly, mariculture is often ravaged by disease or suffers from the accumulation of its own wastes. Therefore, in order to make the best assessment of damages attributed to contamination by oil it is necessary to make comparisons of post-spill recovery results with the conditions which pre-existed the spill or with control areas outside the affected area.