oil/Corexit mixture. These results indicate that: (1) Corexit 9527 is at 

 least as toxic to bird embryos as Prudhoe Bay crude oil, and (2) oil/Corexit 

 9527 mixtures are toxic to bird embryos but the degree of toxicity probably 

 depends on the mixing ratio. However, it is not known whether oil/dispersant 

 mixtures in the form of minute particles dispersed in water can be transfer- 

 red to bird eggs or whether these dispersed particles pose any threat to 

 adult birds. 



One of the two ongoing dispersant studies deals with the transferability 

 of chemically dispersed oil to bird eggs and the effects of dispersant and 

 chemically dispersed oil on bird breeding behavior. Breeding pairs of mallard 

 ducks are being exposed to Corexit 9527, Prudhoe Bay crude oil, a 10:1 crude 

 oil/Corexit mixture, or no contaminant. The test substances are applied to 

 the surface of water in water troughs located in each pen. The substances 

 are applied during the first week of incubation, remain on the water for 2 

 days, and then are removed for the remainder of the incubation period. Nests 

 from each experimental group are being monitored for nest and egg temperatures 

 as an indirect measure of incubation behavior. 



The other ongoing dispersant study concerns the effects of chronic in- 

 gestion of dispersants and crude oil/dispersant mixtures. Mallard ducklings 

 are being fed duck starter mash containing either 1.5 percent Prudhoe Bay 

 crude oil, 1.5 percent of a 10:1 water/Corexit 9527 mixture, 1.5 percent of 

 a 10:1 crude oil/Corexit mixture, or no contaminant. The ducklings will be 

 fed these diets from hatching until they are 18 weeks old. All birds then 

 will be placed on clean feed through the end of their first breeding season. 

 Information will be gathered to evaluate mortality, growth and development, 

 liver and kidney damage, dehydration, hormonal profile, and egg production. 



SUMMARY 



Chemical oil dispersants currently are being evaluated as a method of 

 oil spill control in the United States. Dispersants remove oil from the 

 water surface, prevent the formation of water-in-oil emulsions, reduce the 

 ability of oil to adhere to objects, and permit accelerated deterioration 

 of the oil. However, chemically dispersed oil also has a greater short-term 

 toxicity and a greater ability to penetrate sand and gravel beaches than does 

 nondispersed oil. In addition, chemical dispersants seldom work as well as 

 expected and, from a biologists 's viewpoint, they are an undesirable method 

 of oil spill control. Decisions on the use of dispersants should be made 

 carefully on a case by case basis. 



Corexit 9527 was found to be at least as toxic to mallard embryos as 

 Prudhoe Bay crude oil. The toxic effects of crude oil/Corexit 9527 mixtures 

 appear to increase as the amount of dispersant increases. Studies are under- 

 way to examine the transferability of chemically dispersed oil to bird eggs, 

 the effects of dispersant and chemically dispersed oil on bird breeding be- 

 havior, and the effects of ingested dispersant and crude oil/dispersant mix- 

 tures on avian physiology. 



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