Page 103 - Environmental Control in Petroleum Engineering

90 Environmental Control in Petroleum Engineering

Continued hydrocarbon exposure also lowers the growth rate of animals
(National Research Council, 1985).
Exposure to hydrocarbons can adversely affect the development of
organisms in some species at concentrations below 1 mg/1. Some
species (annelids, gastropods, and copepods) show no long-lasting
damage, while other species (corals, bivalves, and some crustaceans)
can suffer long-term damage at an oiled site (National Research
Council, 1985).
The impact of hydrocarbon exposure also depends on whether the
hydrocarbon is dissolved or dispersed as suspended droplets. For
shrimp, the toxicity of dispersed crude oil was found to decrease with
decreasing amounts of total aromatic hydrocarbons (benzene, alkyl-
benzenes, and naphthalenes). For sand lance fish, however, the impact
could not be tied directly to the concentration of aromatics in the
water. Instead, it was postulated that the oil droplets attached to
their eggs and cut off their oxygen supply (American Petroleum
Institute, 1985a).
One concern with crude oil spills is their potential impact on the
behavior of migratory salmon. Because salmon identify their home
water by smell, there was concern over whether their sense of smell
would be affected by passing beneath a spill so that they could not
recognize their home water. Studies have shown that as long as the
fish pass back into uncontaminated water, their homing ability is not
affected (American Petroleum Institute, 1985b; American Petroleum
Institute, 1986a; American Petroleum Institute, 1987a).
The effects of spilled crude oil on the reproductive success of
Pacific herring (Culpea harengus pallasi) have also been studied
(American Petroleum Institute, 1985a). No effect in fertilization rates
or total percentage of eggs successfully hatched were observed. How-
ever, exposure to oil significantly increased the frequency of abnormal
larvae. These abnormalities included spinal deformities, swollen peri-
cardial regions, and yolk sac compartmentalization. The amount of oil
droplets adhering to the eggs apparently controlled the frequency of
abnormal larvae rather than the total oil concentration in the water. It
was not certain whether this increase of abnormal larvae resulted from
the toxic compounds of the oil passing to the eggs or from oxygen
deprivation from the oil droplets covering the egg.
The most common impact of crude oil on birds is by direct contact,
Oil coats their feathers, causing them to lose their water-repellance