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AMOCO CADIZ POLLUTANTS IN ANAEROBIC SEDIMENTS:
FATE AND EFFECTS ON ANAEROBIC PROCESSES
112
by
1
David M. Ward , Michael R. Winfrey , Eric Beck and Paul Boehm
1) Department of Microbiology, Montana State University, Bozeman,
Montana 59717
2) Energy Resources Company, Inc., Cambridge, Massachusetts 02138
INTRODUCTION
It was estimated that much of the oil spilled after the wreck of
the AMOCO CADIZ impacted intertidal and subtidal sediments (Hann, et
al, 1978; Gundlach and Hayes, 1978). Considerable differences exist
between sediment and aquatic environments which could have dramatic
effects on the persistence of spilled oil and its effects on the native
biology of coastal environments. Recent investigations have shown that
intertidal and subtidal sediments are anaerobic except in the initial
few millimeters near the surface (S^rensen, et al, 1979; Revsbech, et
al, 1980a, b) . Since oxygen is known to be of extreme importance in
the microbial biodegradation of hydrocarbons (Atlas, 1981; Hambrick, et
al, 1980; DeLuane, et al, 1981; Ward and Brock, 1978) it is likely that
the persistence of hydrocarbons would be much greater in anoxic sediments.
This could create a source of relatively unweathered petroleum
for secondary pollution events. One of the major objectives of this
study was to investigate the extent of pollution by AMOCO CADIZ oil in
anaerobic coastal sediments. Evidence for weathering and potential
biodegradation of sediment hydrocarbons under aerobic and anaerobic
conditions was also obtained in chemical and microbiological studies.
Sediments are also important sites where extensive mineralization
of organic matter and recycling of nutrients occurs (Fenchel and J#rgensen,
1977). The effect of oil on sediment microorganisms and processes
has been examined in some studies (Walker, et al, 1975; Knowles
and Wishart, 1977) but only a few studies have examined the effects on
mineralization (Griffiths, et al, 1981, 1981 (in press)). Because of
the extreme thinness of the oxygenated zones of coastal sediments, anaerobic
processes are important in mineralization and nutrient recycling
(S^rensen, et al, 1979). The effects of oil on anaerobic processes
have not been studied . Many studies on sediment chemistry and microbiology
support the model for anaerobic microbial food chains in marine
sediments presented in Figure 1 (see Mah, et al, 1977; Fenchel and J^rgensen,
1977; Rheeburg and Heggie, 1977; Bryant, 1976). Within anaerobic
zones polymeric organic matter is fermented principally to H , CO
and acetic acid. Acetate and H„ are the main energy sources for specialized
anaerobic bacteria which terminate the food chain. The activity
of these terminal groups is thought to be important in influencing
fermenting bacteria to produce mainly acetate, H„ and CO (Bryant,
1976) . The importance of these energy sources in marine sediments has
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