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

S0300-A6-MAN-060the oil which is in contact with the water the opportunity for degradation is enhanced when the oilis spread thinly or dispersed to expose a greater surface area to microbial attack.2-3.1.7 Sinking and Sedimentation. Evaporation, dissolution, oxidation and adhesion of particlesof sediment or organic matter to oil will sometimes increase the density of oil enough tomake it sink. Adhesion to sediments occurs with heavy crude oils, some heavy fuel oils andwater-in-oil emulsions with specific gravities only slightly less than one. These heavy oils, visibleby day when warmed by the sun, may submerge during hours of darkness as they cool andbecome more dense. As sediment and debris adheres to heavy oil, the oil is more likely to sink,become embedded in the ocean bottom and remain there for an extended period. Sinking complicatescleanup operations and poses a danger to bottom-dwelling organisms. This phenomenonoccurs most frequently close to shore, where the water column entrains particulate matter.2-3.1.8 Resurfacing. Density of oil on the seabed may be decreased by anaerobic oxidation.If density is reduced sufficiently, the oil will resurface and be exposed to weathering processeswhich will continue until the oil sinks again or disappears completely.2-4 EFFECTS OF OILThe effects of spilled oil depends upon the quantity spilled, its physical and chemical characteristics,the nature of the environment and prevailing weather. For example, weathered crude or blackoil may sink and impact life on the sea bottom as well as in the water column and intertidal zone.Light oils, on the other hand, tend to remain near the water surface and thus impact marine life onor near the water surface and intertidal region. However, because they tend to be more toxic thanheavy oils and penetrate shoreline soils and porous stone more deeply, light oils cause longlastingenvironmental harm.The extent of damage is not necessarily proportional to the quantity of oil spilled. A small amountof oil in an environmentally sensitive area can cause considerably more damage than more oil ona rocky shoreline. What happens to the environment is a combination of the impact of oil andmeasures taken by response personnel.Response measures mitigate spill effects, but impact the environment in their own ways. Timelybooming may keep oil from impacting environmentally sensitive shorelines. Removing oil bymechanical means may do more damage to the environment than if no response were made. Leavingimpacted marshlands alone can prevent plants from being trampled by well-meaning cleanuppersonnel.Ecological effects from an oil spill include physical contamination of habitats, changes in growth,physiology and behavior of organisms and species, toxicity and increased mortality in plants andanimals and destruction or modification of entire communities of organisms. Effects from an oilspill are more than ecological. The oil spill fouling of recreational areas, industrial facilities,ports, wetlands and wildlife has economic impact; degrading or destroying scenic, natural areashas a negative impact on the quality of life in the region. Negative effects of oil pollution include:2-12