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The detailed gas-chromatographic and mass-spectral analyses of the
samples collected at each site indicated a lack of significant petroleum
hydrocarbons throughout the study at Sites 1, 4, 9, and 10 (Tables 10,
13, 18, 19). Site 2 showed some evidence of weathered hydrocarbons in
1978 and a significant input of fresh petroleum hydrocarbons in July
1980 (Table 11). Site 3 had significant concentrations of weathered
petroleum origin throughout the study (Table 12). Sites 5 and 6 showed
an alteration of the hydrocarbon mixture with time that indicated the
occurrence of biodegradation (Tables 14, 15). Samples at Sites 7 and 8
continued to show the presence of a relatively unweathered hydrocarbon
mixture up to two years following the AMOCO CADIZ spill (Tables 16, 17).
It appears that undegraded hydrocarbons were seeping into the surface
sediments at Site 8 and it is postulated that either shifts in the
sediment were repeatedly exposing hydrocarbons that had been protected
from microbial degradation and/or that some oil continued to be washed
ashore from the sunken AMOCO CADIZ vessel. Site 11 showed clear
evidence of heavy oiling from the TANIO spill which persisted for a year
following the spill (Table 20) . The offshore sites sampled in November
1979 in the Bay of Morlaix failed to show the presence of AMOCO CADIZ
oil.
TABLE 10. Hydrocarbon concentration ng/g.
SITE 1
C-# 12-78 3-79 8-79 11-79 3-80 7-80 6-81
14