effects of additional heavy oiling. This may be a result of an adapta- 

 tion of microorganisms to the presence of oil, or to a selection of oil 

 resistant populations. 



It is not surprising that hydrocarbons did not directly inhibit 

 sulfate reduction since this process appears to be active in oil forma- 

 tion waters (Bailey, et al., 1973; ZoBell, 1958). However, it was sur- 

 prising that compounds which inhibited acetate oxidation did not dir- 

 ectly inhibit sulfate reduction, as other investigations have pointed 

 to the importance of acetate as a substrate for sulfate reduction (Win- 

 frey and Ward, submitted; S<f>rensen et al, 1981; Banat and Nedwell, per- 

 sonal communication). 



The chemistry of hydrocarbons present in the various sediments one 

 year after the spill indicated the presence of oil highly altered by 

 evaporation and biodegradation. The levels observed in the environment 

 were also lower (0.1-1 mg/g) than the levels added in our experiments 

 to simulate heavy oiling (50-250 mg/g). It is possible that a tempor- 

 ary inhibition of acetate oxidation could have resulted from very heavy 

 oiling of relatively fresh oil. Such conditions could have existed at 

 all polluted sites immediately following the AMOCO CADIZ spill, al- 

 though rapid loss of volatile compounds probably occurred between 

 spillage and beaching of oil (Dowty, et al, 1981; Ward, et al, 1980). 

 Any inhibitory effect would then have been reduced as cleanup or trans- 

 port of hydrocarbons out of the sediments decreased hydrocarbon amount, 

 and as evaporation, dissolution and biodegradation altered the remain- 

 ing sediment hydrocarbons. By the time site comparison experiments 

 could be performed, recovery from any negative effects which might have 

 occurred had apparently taken place. The inhibitory effects on acetate 

 oxidation we observed may be significant in extremely cold regions 

 where slow rates of evaporation would occur. 



ACKNOWLEDGEMENTS 



We are indebted to the Centre Oceanologique de Bretagne at Brest 

 and the Station Biologique at Roscoff for providing laboratory space 

 and assistance. We also thank Bob Clark of the NOAA National Analyti- 

 cal Facility for supplying AMOCO CADIZ mousse, George Ward of Exxon 

 Corp. for supplying the light Arabian crude oil, and Dale Meland and 

 Melinda Tussler for technical assistance. 



This study was part of a joint effort undertaken by the Centre Na- 

 tional pour 1' Exploitation des Oceans (CNEXO) of the French Ministry of 

 Industry and the NOAA of the U.S. Department of Commerce to study the 

 ecological consequences of the AMOCO CADIZ oil spill. It was financed 

 by funds given to NOAA (contract NA 79RAC00013) by the Amoco Transport 

 Company and by the NOAA Outer Continental Shelf Environmental Assess- 

 ment Program, through an interagency agreement with the Bureau of Land 

 Management. 



186 



