The quantity and type of oil spilled determine, to a great extent but not
exclusively, the significance of the impact on the marine environment.
A spill of several thousand tonnes will cause a lot more damage to the aquatic environment than a spill ten times smaller, although the oil type will play a significant part in the nature and extent of any damage caused.
A spill of heavy fuel oil is likely to cause much more damage than a crude oil spill of a corresponding size. A spill of a slightly evaporable substance will in the same way be more damaging for the sea and the foreshore than a spill of a highly evaporable substance.
The duration of spillage also plays an important role. A sudden violent release will concentrate the effects on a smaller area than a long, slow leak. Furthermore, if the effects are brutal, they may not be as likely to last as long.
The spill location is a fundamental factor in its impact. A spill in the open sea, such as that of the Prestige, will lead to limited impact spread over a very vast length of shoreline, over a long period, whereas a spill on the coast will have a massive effect over a more limited distance.