Environmental Engineering Reference
In-Depth Information
Figure 4.2 Oil Spill Influences on Seabirds
Decreased
population size;
altered population
structure
No response
Initial oiling
Direct mortality
Indirect mortality
Secondary
release of oil
Food supply
reduced; foraging
behavior altered
OIL SPILL
Lowered
reproductive
success
Emigration
Cleanup
activities
Physiological
stress
Reduced habitat
occupancy and
use
Habitat quality
reduced
Source: NRC 1985, 121.
dissolved in petroleum and are released during extraction, contributing to the total load of hydro-
carbon input to the seas (3). Some, such as polycyclic aromatic hydrocarbons (PAH) are known
human carcinogens, and others are highly toxic to marine organisms. According to the National
Research Council, “the more turbulent the release (i.e., if it is during a storm or from a blowout
or pipeline under pressure), the higher the relative concentrations of the more toxic PAH, and the
higher the impacts to water column organisms” (NRC 2003, 140).
No spill of petroleum is benign (NRC 2003, 4). Oil can kill marine organisms, reduce their
fitness through sublethal effects, and disrupt the structure and function of marine communities
and ecosystems (120). The effect of petroleum releases into the natural environment is a complex
function of the rate of release, the nature of the released petroleum, the proportions of toxic com-
pounds it may contain, and characteristics of the local ecosystem exposed to it (4). For example,
the complex effects of oil spills on seabirds are illustrated in Figure 4.2. Similar pathways for the
impact of oil spills would be evident for marine mammals, fishes, mollusks, and other benthic
organisms. After an oil spill, birds, mammals, and reptiles are primarily impacted by direct exposure
to floating oil, ingestion of contaminated prey, or depletion of food resources (139).
Much of what is known about the fate and effect of spilled oil has been derived from a very
few well-studied spills. Although there is now good evidence for the toxic effects of oil pollution
on individual organisms and species composition of affected communities, little is known about
the effects of either acute or chronic oil pollution on entire populations or on the functions of
communities or ecosystems (NRC 2003, 4). For example, we do not know the upper boundary for
the potential length of a long-term effect of oil pollution, which is likely to be at least the length
of a generation of affected organisms and may be much longer (119). Spill clean-up activities are
also harmful to some organisms and ecosystems.
Sublethal effects from hydrocarbon exposure occur at concentrations several orders of magnitude
lower than those that induce acute toxic effects (Vandermeulen and Capuzzo 1983). Impairment of
feeding mechanisms, growth rates, development rates, energetics, reproductive output, recruitment
 
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