FISHERY BULLETIN: VOL. 72, NO. 3 



appears to be universally lacking is the difficult 

 research leading to an understanding of chronic 

 and sublethal effects of oil at the biological com- 

 munity level. The following discussion outlines 

 these complexities and points out how they make 

 most generalizations invalid and the extrapola- 

 tion of most data dangerous. 



DESCRIPTION OF OIL 



Crude oil is a complex mixture of many different 

 specific hydrocarbons and a variety of compounds 

 containing sulfur, oxygen, nitrogen, and some 

 trace metals. Hydrocarbons make up the bulk of 

 crude oil and can roughly be placed into one of 

 three classes: paraffinic, naphthenic, and aromat- 

 ic. From one area to another, crude oils vary in 

 their composition and in density, volatility, and 

 solubility. Their relative toxicity will vary (Ott- 

 way, 1971) but is roughly proportional to their 

 aromatic content. 



Paraffinic (or aliphatic) hydrocarbons are 

 straight or branched carbon chains and are satu- 

 rated (thus no carbon-carbon double bonds) with 

 hydrogen or other groups. These hydrocarbons are 

 the least toxic, although they may have an 

 anesthetic or narcotic effect if concentrations are 

 great enough. 



Naphthenic compounds (cycloparaffins) contain 

 at least one ring structure that is saturated. With 

 this base, more rings or chains may be attached to 

 form a variety of complex molecules. 



Aromatic hydrocarbons also contain a ringed 

 structure, but the ring is unsaturated with hy- 

 drogen and contains carbon-carbon double bonds 

 (benzene ring). The simplest aromatic is benzene, 

 which is very toxic and relatively water soluble in 

 comparison to most hydrocarbons found in crude 

 oil. Benzene and other low-boiling aromatics are 

 the most toxic petroleum fractions. High-boiling 

 aromatics act as slower poisons than low-boiling 

 aromatics, but they are equally severe in their 

 effect. In addition, some are known to induce 

 cancer; 3,4-benzpyrene, 1,2-benzanthracene, and 

 some alkylbenzanthracenes have been isolated 

 from crude oil, and their carcinogenic effects on 

 animals and man have been demonstrated 

 (Blumer, 1970).^ 



^Blumer, M. 1970. Scientific aspects of the oil spill problem. 

 Presented at NATO Conference, Brussels, 6 Nov. 1970, 21 p., 

 Woods Hole Oceanogr. Inst., Woods Hole, Mass. 



Olefinic hydrocarbons (paraffinlike but unsatu- 

 rated and containing reactive carbon-carbon dou- 

 ble bonds) are not generally found in crude oils but 

 are plentiful in certain gasolines and other refined 

 products. The fate of olefins in the marine envi- 

 ronment is poorly understood, but this class of 

 compounds may be quite reactive under certain 

 conditions and may combine readily with hy- 

 drogen, oxygen, chlorine, sulfur, and other ele- 

 ments to produce toxic substances. Once incorpo- 

 rated into organisms, olefins may remain intact 

 for surprisingly long times (Blumer, 1967). The 

 full range of olefinic hydrocarbons probably inter- 

 feres with the reception of chemical messengers, 

 or odors, in the sea by certain marine organisms 

 (Blumer, 1970, see footnote 3). 



When crude oil is processed ("cracked"), olefins 

 and other compounds for gasoline and fuel oils 

 may be formed or separated. Fuel oils, commonly 

 involved in spills, are rated from 1 to 6. Those 

 rated 1 are the lightest, most volatile, and most 

 toxic and have the greatest aromatic concentra- 

 tions; those rated 6 are the least volatile, least 

 soluble, and least toxic and are asphaltic (tarlike). 



Hydrocarbons are not foreign to the marine en- 

 vironment; normal paraffins are synthesized by 

 most, if not all, living organisms. Blumer, Guil- 

 lard, and Chase (1971) characterized the natural 

 hydrocarbon content of 22 species of phytoplank- 

 ton and cited literature for zooplankton. There are 

 certain characteristic differences, however, be- 

 tween hydrocarbons native to organisms and the 

 hydrocarbons in petroleum, particularly in the rel- 

 ative distribution of the various hydrocarbons. 

 Crude oils and certain petroleum products are 

 complex mixtures that contain molecules of dif- 

 ferent sizes in ratios not found in any one species of 

 organism. Certain specific paraffins, and some 

 naphthenic and aromatic compounds, are rarely 

 found in organisms not exposed to oil pollution. 

 These characteristic differences have been the 

 basis for several scientific papers (Blumer, Souza, 

 and Sass, 1970; Ehrhardt, 1972; Clark and Finley, 

 1973; and others). 



FACTORS INFLUENCING 

 THE IMPACT OF OIL 



The impact of oil on the marine environment is 

 governed by several factors — physical, chemical, 

 and biological — in addition to the inherent com- 

 plexity of crude oil and refined products. The be- 

 havior, effects, and fate of an oil spill involve all of 



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