U.S. Navy Ship Salvage Manual Volume 6 - Oil Spill Response

S0300-A6-MAN-060• Direct kill of organisms through coating and asphyxiation.• Direct kill of organisms through contact poisoning.• Direct kill of organisms through exposure to water soluble toxic components of oil atsome distance from the oil spill and/or some time after the incident.• Destruction of food sources for animals higher in the food chain.• Destruction of juvenile organisms that are generally more sensitive to pollution.• Sublethal exposure of organisms resulting in reduced resistance to infection and otherstresses.• Destruction of commercial value of food fish and shellfish by oil tainting.• Introduction of carcinogens and cumulative toxins into the marine food chain andhuman food sources.• Low-level effects that may interrupt the events necessary for the survival and reproductionof marine species.2-4.1 Physical Contamination. Oil on the water surface may contaminate mammals and birdsthat populate that area. This contamination is more likely to occur in coastal areas than on theopen ocean. Shorelines may be coated with oil. The degree of contamination depends on the physicalcharacteristics of the shoreline. Oil may penetrate a gravel or sand beach to several incheswhile coating only the surface of a rocky coastline. Oil dispersed throughout the water column oremulsified, can contaminate fish and fishing gear.2-4.2 Toxicity. It is difficult to quantify the toxicity of oils because they may consist of thousandsof different compounds of varying toxicity. Mortality in test organisms exposed to differentcrude oils has been as low as 1 percent and as high as 89 percent. In general, the lighter petroleumfractions are more toxic to marine life than heavier oils. Many low boiling point aromatics, suchas benzene and toluene, are deadly poisons to almost any form of life, while some higher boilingpoint paraffins are essentially nontoxic. Less persistent than heavy oils, the light components ofoil are present in greater proportions during the initial stage of a spill than they are after some timehas passed. The lighter components evaporate quickly from the sea surface and leave little residue.The effects of the toxic components of oil on marine life can be severe if a spill occurs during apeak period of animal reproduction. The impact may last for several reproduction cycles if oilssink into the bottom sediment where oils may be retained for several years.The toxicological effects of oil may be transient if oil remains on the water surface and does notimpact the shore.2-13