Environmental Effects

The effects of an oil spill will depend on a variety of factors including, the quantity and type of oil spilled, and how it interacts with the marine environment. Prevailing weather conditions will also influence the oil’s physical characteristics and its behaviour. Other key factors include the biological and ecological attributes of the area; the ecological significance of key species and their sensitivity to oil pollution as well as the time of year. It is important to remember that the clean-up techniques selected will also have a bearing on the environmental effects of a spill.

Oil spills may impact the environment in the following ways:

• Physical smothering of organisms: This is caused by oils with a high viscosity, in other words heavy oils. Smothering will affect an organism’s physical ability to continue critical functions such as respiration, feeding and thermoregulation.
• Chemical toxicity: This is characteristic of lighter chemical components  which are more bio-available, ie absorbed into organs, tissues and cells, and can have sub-lethal or lethal toxic effects.
• Ecological changes: This is caused by the loss of key organisms with a specific function in an ecological community. They can be replaced by different species undertaking similar functions in which case the implications for the ecosystem as a whole may not be severe. However, more detrimental is the niche in the community being replaced with organisms performing completely different functions thereby altering the ecosystem dynamics.
• Indirect effects: Loss of shelter or habitat through oiling or clean-up operations.

Extensive research and detailed post-spill studies have shown that even major oil spills will rarely cause permanent effects.

Marine ecosystems have high natural variability and are subject to ever-changing environmental phenomena such as storms, climatic anomalies (eg El Niño) as well as anthropogenic pressures. Furthermore, marine organisms have varying degrees of natural resilience to these pressures on their habitats. This natural variability means it is unlikely that exact pre-spill conditions will be reached. It makes determining the point of recovery following an oil spill, and the time it will take, difficult to accurately predict.

It is generally accepted that recovery is reached when a community of plants and animals characteristic of that habitat are established and functioning normally.