Table 9 reports the effect of these oil and aromatic additions on 

 sulfate reduction rates in lie Grande surface sediments. At the unoiled 

 control site, all oil additions decreased the rate of sulfate reduction 

 although not significantly below the control (p ^ 0.16). The greatest 

 inhibition was observed for toluene and benzene additions (p = 0.10 and 

 0.09 respectively). At the oiled site, rates under all conditions were 

 not significantly different from the control rate. The effect of the 

 oil, benzene, and toluene additions on methanogenesis (results not 

 shown) were variable. None of the additions resulted in a rate of 

 methanogenesis that was significantly different than the rate without 

 additions . 



TABLE 9. Effect of Hydrocarbons on Sulfate Reduction in Marsh Sedi- 



- a 

 ments 



Sediment samples were collected in April, 1980. 



Rates are the mean of 3 replicates and expressed as |jmoles S0,-S/ml/d. 



14 

 The effect of the oil and aromatic additions on [2- C] -acetate 



oxidation to CO in He Grande is shown in Table 10. At both the 

 oiled and unoiled site, the amount of C0„ produced in 2 h was signi- 

 ficantly reduced (p S 0.01) with all of the additions. In general, the 

 magnitude of inhibition was greater at the control site (76-97%) than 

 at the oiled site (51-93%). In both sites inhibition was greatest with 

 the unweathered oil and decreased with the extent of weathering of the 

 oils . 



181 



