biological impact in intertidal areas, shallow estuaries, and 

 wetlands. 



2) Dispersant-treated oil may penetrate deeper into sand and 

 gravel on beaches and cause more oil to be lodged below the beach 

 surface than would occur with untreated oil (Hayes and Gundlach 

 1978). 



3) Dispersants may not work as well as expected. Experiments have 

 shown that more dispersant is usually needed to satisfactorily dis- 

 perse the oil than the manufacturers suggest (Swedmark et al . 1973, 

 Linden 1975, Wells and Keizer 1975, Gill 1977, Dalla Venezia and 

 Fossato 1977, Smith and Holliday 1979). This reduced effectiveness 

 may be caused by bad weather, application problems, inappropriate 

 use of the dispersant, insufficient water turbulence to keep oil 

 particles from rising, or overly optimistic estimates of dispersant 

 effectiveness by the manufacturer. 



4) The use of chemical dispersants is basically unappealing to 

 wildlife biologists. Dealing with environmental contamination 

 by a toxic substance whose biological effects are only partially 

 understood is difficult. To deal with such a contaminant by apply- 

 ing large amounts of another toxic substance whose effects are 

 also only partially understood may appear to be a risky venture. 



It is clear that decisions on the use of dispersants should be made 

 carefully on a case-by-case basis. 



EFFECTS OF OIL DISPERSANTS ON BIRDS 



Little was known about the effects of oil dispersants or chemically 

 dispersed oil on birds until experiments were initiated at the Patuxent Wild- 

 life Research Center in 1978. I will briefly present the results of a re- 

 cently completed study of the effects of Corexit 9527 dispersant and oil/ 

 Corexit 9527 mixtures on egg hatchability. I also will describe two other 

 studies that are in progress. The egg hatchability study will be reported 

 in detail elsewhere (Albers, in preparation). 



In the egg hatchability study, artifically incubated eggs of the domes- 

 tic mallard {Anas platyrhynohos) were treated on the sixth day of incubation 

 with 1, 5, or 20 microliters (ul ) of Prudhoe Bay (Alaska) crude oil, Corexit 

 9527, a 5:1 oil/Corexit 9527 mixture, or a 30:1 oil/Corexit 9527 mixture. 

 All were applied to the surface of the egg with a microliter syringe. 

 Nothing was applied to the control eggs. All four substances caused a sig- 

 nificant (P< 0.01) reduction in egg hatchability at the 20 wl level. Corexit 

 9527 and the 5:1 oil/Corexit 9527 mixture also caused a significant reduction 

 in egg hatchability at the 5 u\ level. The 5:1 oil/Corexit 9527 mixture 

 caused the death of embryos earlier than did the Corexit 9527 and the 30:1 



69 



