amount of contaminant in each phase of the experiment (Tarshis, in prepara- 

 tion). The results from these experiments have supported the hypothesis that 

 transfer of aromatics through a simple aquatic food chain is another route 

 for oil contamination to reach waterfowl. 



Taken together, the results from the studies described suggest that, to 

 a degree, adult ducks ingesting oil with their food may be able to make 

 physiological compensations. There may be damage to organ systems, however, 

 that directly affects the ability of the bird (especially the young) to sur- 

 vive a second environmental challenge (Holmes, Gorsline, and Cronshaw 1979). 

 There is also some evidence that oil ingestion by adults affects egglaying 

 (Holmes, Cavanaugh, and Cronshaw 1978; Coon and Dieter, in preparation). 

 Studies are underway at the Patuxent Center to further define this reproduc- 

 tive effect. 



Incubator Studies 



Incubators were used as an aid to study the effects of microliter (pi) 

 quantities of crude and No. 2 fuel oils on developing avian embryos. A 

 technique was developed in which oil was externally applied in precise amounts 

 (ranging from 1 to 50 pi) to discrete areas of bird eggs (Szaro and Albers 

 1977, Albers 1977, 1978). The eggs were subsequently placed in an incubator 

 maintained at optimum temperature and humidity. Eggs were routinely candled 

 to monitor mortality and embryo development. Surviving embryos were ex- 

 amined at 18 days of age or permitted to hatch. External applications of 

 oil were found to increase mortality and incidence of defects and stunting 

 in mallard embryos (Eastin and Hoffman 1978; Hoffman 1978a, 1978b_, Hoffman 

 1979a). In addition, a dose:mortal ity relationship was shown. Eggs from 

 other species were collected from coastal areas and brought back to the 

 laboratory (Szaro and Albers 1977, Coon et al . 1979, White et al . 1979). 

 When these eggs were dosed with oil, as in the previous studies, the mortality 

 was not as great. One major difference between the two studies was that the 

 mallard eggs were synchronous in development, whereas field-collected eggs 

 were at various stages of embryo development. Laboratory studies were per- 

 formed to investigate the possibility that there is a differential sensi- 

 tivity to external oiling during development. The results were clearcut and 

 indicated high mortality at two distinct periods early in the development, 

 but that egg oiling after this critical time had little effect. 



It also was decided to examine in detail certain suspect trace metals 

 and those components chemically identified in the aromatic hydrocarbon 

 fraction of crude oil to try to further understand the toxicity to embryos. 

 The porphyrin forms of vanadium and nickel found in crude oil are much less 

 toxic to embryos than are some of the salts previously tested on birds and 

 mammals. These porphyrin forms did, however, produce some defects in 

 embryos (Hoffman 1979b_). And mercury, if present in sufficient quantity, 

 was toxic (Hoffman and Moore 1979a, 1979b). Of the aromatic fraction com- 

 ponents, the polycyclic aromatics including chrysene, benzo(a)-pyrene, and 

 dimethyl benzanthracene produced high mortality in embryos (Hoffman 1979^, 

 Hoffman and Gay, in preparation). The incubation experiments just described 



62 



