plants depend on both toxic and coating effects, frequency of coating and 

 on the time of year [173]. 



Toxic effects of oil on larval stages of many marine organisms 

 show that larvae are 10 to 100 times more sensitive to oil than adults. 

 Typically, larvae may develop abnormally, leading to death several weeks 

 after exposure. Such malformed individuals are usually more susceptible 

 to predation, and unsuccessful in competition for food. Larvae tend to 

 be more sensitive than eggs [173]. 



Bivalves, including oysters, clams, cockles and mussels are moderately 

 oil resistant. The ability to close and seal their shells apparently 

 provides protection. However, this closed condition cannot be maintained 

 indefinitely. In fact, cockles tend to "gape" making them more susceptible, 

 Light crude oils and some petroleum products may be able to penetrate the 

 minute shell openings through which mussels secrete the byssus threads 

 that attach them to rocks [173]. 



Coating : Organisms most endangered by coating are those unable to 

 leave the area where weathered oil is emulsified, dispersed in the water 

 column, settled to the bottom, or coats the shore. This immediately 

 excludes most finishes and other mobile pelagic organisms, which can detect 

 low concentrations of oil in seawater and usually avoid higher concentra- 

 tions. However, some fish larvae (such as herrings) may not be able to 

 avoid oil and lobsters are known to be attracted. Birds and marine 

 mammals present different problems since they may not recognize an oil 

 slick until coating is inevitable or has already occurred [174]. Whether 

 or not an organism can move away from oil deposited on the ocean bottom 

 plays a large role in determining whether or not it survives the 

 exposure. 



In many filter-feeding organisms (such as clams, snails, barnacles, 

 and shrimps) the feeding and respiratory organs are closely coupled. 

 Therefore, interference with one almost inevitably affects the other. 

 Many shellfishes filter water through their gills and strain out every- 

 thing. Indigestible material is formed with mucous and ejected. As 

 long as the amount of oil is small, the organisms is usually able 

 to surround the oil with mucous and eject it. A heavier emulsion will 

 probably suffocate the organism [174]. Subtidal benthic species are 

 somewhat protected from coating because oil does not occur as a film on 

 subtidal substrates except in the worst local spill situations [5]. 



Warm-blooded marine organisms must maintain their body temperatures 

 within a narrow range, often at a higher level than the surrounding water. 

 This requires an efficient insulating layer surrounding the body. Whales, 

 seals and walruses use a thick layer of blubber for insulation which is 

 little affected by a coating of oil. Fur seals and sea otters combine 

 fat layers with a thick fur coat as insulation. A coat of oil can 

 significantly change the fur's insulating properties perhaps causing the 



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