147, 156, 170, 178, 184, 192, 198, 206, 212, 220, and 226. The 

 representative compounds were naphthalene, methyl naphthalene, HMB as an 

 interanal standard, dimethyl naphthalene, trimethyl naphthalene, 

 phenanthrene, dibenzothiophene, methyl phenanthrene, methyl 

 dibenzothiophene, dimethyl phenanthrene, dimethyl dibenzothiophene, 

 trimethyl phenanthrene, and trimethyl dibenzothiophene, respectively. 

 The dwell time per ion was 10 msec. Instrument response factors were 

 calculated by injecting known quantities of unsubstituted and C and C„ 

 substituted authentic aromatic hydrocarbons and determining the 

 integrated response for each compound. These values were used to 

 extrapolate for quantitation of isomers and C_ substituted compounds. 



For analysis of the polar fraction including microbial degradation 

 products, three samples were selected for analysis by the University of 

 New Orleans Center for Bio-organic Studies. The samples were: 1) flow 

 through, 6 week incubation from site 6; 2) flow through, 6 week 

 incubation from site 7; 3) agitated flask, 6 week incubation from site 

 7. Frozen samples were sent for analysis. At the Center for 

 Bio-organic Studies the samples were extracted with successive portions 

 of CH OH, CH OH/CH CI and CH CI . The extracts were fractionated using 

 silica gel and the f_ fraction was collected, methylated and analysed by 

 high resolution GC-MS . 



RESULTS AND DISCUSSION 



The enumeration of hydrocarbon utilizing microorganisms indicated 

 that numbers of hydrocarbon utilizers in the intertidal sediments 

 increased significantly in response to hydrocarbon inputs (Table 2). 

 Site 3, which is covered with seawater only at times of extreme high 

 tide, showed very high populations of hydrocarbon utilizing 

 microorganisms even three years after the AMOCO CADIZ spillage. Sites 5 

 and 6 (located within Aber Wrac'h) and Sites 7 and 8 (located near 

 Portsall) showed variable, but apparently elevated, numbers of 

 hydrocarbon utilizers for up to two years following the spill. It 

 appears that hydrocarbons contained within the mud sediments of Aber 

 Wrac'h continued to exert a selective pressure on the microbial 

 community that favored elevated populations of hydrocarbon utilizers for 

 a longer period of time than sites on high-energy sand beaches. Site 2 

 showed evidence that the TANIO spill impacted the lie Crande region. 

 This site did not show elevated numbers of hydrocarbon utilizers in 

 December 1978 or at later sampling times as a result of the AMOCO CADIZ 

 spill, but in July of 1980, several months after the wreck of the TANIO, 

 numbers of hydrocarbon utilizers were greatly elevated. A year later, 

 however, the numbers of hydrocarbon utilizers had returned to background 

 levels at this site. The unoiled control sites 9 and 10 and sites 1 and 

 4, which were impacted by the AMOCO CADIZ spill, did not show any 

 evidence of elevated hydrocarbon-utilizing populations during the 

 sampling period. Similarly, the offshore sites A-D in the Bay of 

 Morlaix did not appear to be elevated at the time of sampling in 

 November 1979. Sites 11 and 12 were added following the wreck of the 

 TANIO and showed obviously elevated populations of hydrocarbon utilizers 

 that persisted for over a year. 



