Climatic and Seasonal Changes 



Certain seasons are more critical than others in terms of the biological 

 activity of aquatic life. For most aquatic species, spring and summer are sea- 

 sons for mating and reproduction. Waterborne embryos and larval stages of 

 many aquatic species, both invertebrate and finfish, are more sensitive to oil 

 than the adult members of the species. Entire year classes of a particular 

 species could potentially be eliminated or severely decimated if a spill were 

 to occur when the young were within the affected area. From a physical stand- 

 point, winter and fall are critical seasons because strong winds usually pre- 

 dominate, which could move spilled oil into areas that might not otherwise 

 become contaminated. 



Indigenous Biota 



From a biologist's point of view, all aquatic species in or near an 

 oil spill area are of equal importance in terms of the extent and severity 

 of damage sustained. In this respect, species of commercial or recreational 

 importance are no more significant than other, smaller organisms that are 

 part of the complex and delicately balanced ecosystem. These smaller organisms 

 form the base of the aquatic food chain and play a vital role in maintaining 

 the integrity and balance of the entire ecosystem. 



TREATMENT METHODS USED TO CLEAN UP 



Since the major oil spill involving the Torrey Canyon in 1967, the U.S. 

 oil companies have made extensive use of chemicals to disperse an oil spill. 

 Use of these dispersants merely compounds the immediate impact of the spilled 

 oil. Although it is true that the second generation oil dispersants now 

 in use are less toxic as a whole, the fact remains that these dispersants 

 entrain, throughout the water column, oil that would otherwise have remained 

 on the surface. The oil is not changed chemically; it still retains its 

 inherent toxicity, which the chemicals disperse in all directions. 



Steam-cleaning of contaminated attached biological communities has an 

 equally devastating impact. The use of steam in previous cleanup efforts 

 has had a serious impact on mucelage-covered algae species, for example, 

 which have some natural protection against the adhesion of oil. Today, high- 

 pressure water is frequently used to clean contaminated rocky shores. This 

 has less of an impact on indigenous species and allows the natural forces 

 of currents, wind, and tidal action to remove adhering oil from contaminated 

 algae and other attached populations. 



Previous Exposure of Spill Area to Oil Pollution 



Biological populations that are under stress from repeated oil spills 

 within an area, which in terms of volume may be minor, will be affected more 

 than those species that have been exposed to only a single spill. The degree 

 of impact is a function of the timing and intensity of these repeated spills. 

 For instance, oiled hard surfaces will not be colonized so easily by attached 

 populations. Oily, contaminated sediments have residual toxicity to inverte- 

 brate larvae. In West Falmouth, for example, the highly contaminated sediments 



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