EVANS and RICE: EFFECTS OF OIL ON ECOSYSTEMS 



found that the nine different crude oils were not 

 degraded as rapidly as purified mineral oil. 

 Glaeser and Vance's studies were with microor- 

 ganisms from the surface water of the Chukchi 

 where small numbers of bacteria may have been 

 present. Furthermore, the observations of 

 Straughan (1971), who noted the apparent lack of 

 biological damage by the Santa Barbara blowout, 

 may apply here. She discussed the possibility that 

 the fauna had an unusually high tolerance for oil, 

 probably because of adaptation from chronic low- 

 level oil exposures from local natural seepages. 

 The observations of ZoBell and Agosti (1972) on 

 the oxidation rates of oil at — 1°C may be an exam- 

 ple of similar adaptive response by the North 

 Slope bacteria collected near natural seeps. These 

 oxidation rates and other adaptive responses 

 might not occur from organisms that have not 

 been preacclimated to chronic low-level exposures 

 of oil and may explain why Glaeser and Vance 

 obtained reports of negligible oxidation rates at 

 0°C from microorganisms from surface water of 

 the Chukchi Sea. Robertson et al. (1973) esti- 

 mated hydrocarbon-oxidizing bacteria popula- 

 tions were in the order of 1/ml in Cook Inlet and 

 Port Valdez, but less in the Arctic Ocean. Num- 

 bers decreased with salinity in Cook Inlet and 

 with depth in Port Valdez. 



ZoBell (1963) reported that oil is readily ad- 

 sorbed by clay and silt and suggests that although 

 adsorption of oil by solids renders the oil more 

 susceptible to autobial and microbial oxidation, 

 almost no bacterial decomposition occurs after 

 burial in the bottom sediments, probably because 

 the environment is anaerobic. Blumer and Sass 

 (1972) found that some paraffmic hydrocarbons 

 remained in bottom sediments 2 yr after the West 

 Falmouth oil spill and aromatic hydrocarbons 

 were prominent, which suggests that these more 

 toxic compounds are utilized by bacteria to a 

 minimum degree. 



Oil in Sediments 



The effect of oil in sediments is poorly under- 

 stood, although several authors have quantitated 

 oil concentrations and noted its persistence. Scar- 

 ratt and Zitko (1972) observed little diminution of 

 bunker C oil concentration from soft sediments 26 

 mo after the wreck of the tanker Arrow. The oil 

 reached maximum concentrations in coarse sedi- 

 ments 1 yr after the spill, but the concentrations 

 reduced thereafter. Chemical degradation can 



occur but is normally restricted to the surface 

 layer of the bottom penetrated by ultraviolet light. 

 Blumer and Sass ( 1972) noted that "The preserva- 

 tion of hydrocarbons in marine sediments for 

 geologically long time spans is one of the accepted 

 key facts in current thought on petroleum forma- 

 tion." However, in spite of the stability of hy- 

 drocarbons in marine sediments, there are charac- 

 teristic differences between the hydrocarbons in 

 polluted and unpolluted areas. Tissier and Oudin 

 (1973) found that hydrocarbons in polluted sedi- 

 ments differed from those of unpolluted sediments 

 by having lower percentages of heavy compo- 

 nents, by not having an odd carbon dominance in 

 the n-alkanes, and by having polycyclic aromatic 

 hydrocarbons with alkyl chains. 



Oil residues were observed on sandy beaches by 

 ZoBell (1963) and in marshes and in sediments of 

 the deepest area (15.3 m) near the West Falmouth 

 spill by Blumer, Sass, Souza, Sanders, Grassle, 

 and Hampson (1970).^ About 2 wk after fuel oil 

 was spilled at Resolute Bay, Northwest Territory, 

 in August 1970, casual sampling revealed that oil 

 penetrated into beach material to a depth of about 

 3 inches (7.6 cm) (Barber, 1971). Oil may be buried 

 and stay intact for a considerable time, even at the 

 higher temperature of the California coast 

 (ZoBell, 1963). During laboratory experiments, 

 Johnston (1970) determined oil decay rates in 

 sand columns contaminated with various concen- 

 trations of oil. Ten percent of the oil was oxidized 

 over a period of several months; the remaining 

 90% decayed much slower. 



The West Falmouth spill provided a unique op- 

 portunity for a study of the immediate and long- 

 term effects of an oil spill on an area where the 

 previously existing environmental base was well 

 known (Blumer, Sanders, Grassle, and Hampson, 

 1971). One effect of the oil was to reduce the cohe- 

 sion of bottom sediments of tidal marshes and the 

 estuary by killing the benthic plants and animals 

 (Blumer, Sass, Souza, Sanders, Grassle, and 

 Hampson, 1970, see footnote 4). The resulting ero- 

 sion spread hydrocarbons to new areas, where the 

 process was repeated. Because of the stability and 

 persistence of the hydrocarbons in marine bottom 

 sediments, Blumer, Souza, and Sass (1970) noted 

 that hydrocarbons may be returned to the bio- 

 sphere by organisms living and feeding in the sed- 

 iments. This redistribution of hydrocarbons can be 



■'Blumer. M., J. Sass, G. Souza, H. Sanders, F. Grassle, and G. 

 Hampson. 1970. The West Falmouth oil spill. Unpubl. manuscr. 

 Woods Hole Oceanogr. Inst., Ref. No. 70-44, 32 p. 



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