333 



In the case of large spills, mass kills of planktonic larvae coming in contact with 

 oil at the surface would be expected. The depth to which toxicity would occurr 

 would depend upon the physical and chemical processes dispersing the oil, while 

 the concentrations of oil components necessary to be toxic would depend in part 

 upon the species involved, their developmental stage, and metabolic rates as in- 

 fluenced by temperature. Sunken oil from spills could render bottoms unin- 

 habitable for larval setting and probably would adversely affect ^ large pro- 

 portion of the adult animaLs producing planktonic larvae. 



Because many planktonic forms are short-lived and drifting organisms, in 

 the case of short-term local iwUution such as oil spills, new healthy populations 

 may be carried in from adjacent unaffected areas (MUeikovsky, 1970). Although 

 the new populations may not have the same composition as the old, recovery 

 time is apt to be short for plankton that complete their life cycle drifting in the 

 water mass. It may take several years, however, for the benthic populations 

 which provide the plankton that migrate daily from surface to bottom to be 

 re-established if the substrate is affected by a spill. 



Chronic oil pollution on zooplankton may have sublethal effects. Toxic hydro- 

 carbons may be concentrated by zooplankters (Mallet and Sordau, 19C4 ; Millet 

 and Lame. 196.") ; both cited in Mironov, 1968) and be passed up the food chain 

 in the same manner as are insecticides and heavy metals. Carcinogenic effects 

 from chronic pollution may occur in the plankton as already demonstrated in 

 benthic bryozoans (Powell et al.. 1970). Plankton populations and their im- 

 portance to the biological community may also be adversely affected by the 

 lowered production of planktonic larvae by the benthic adults. Adequate studies 

 on oil pollution and its effect on the reproductive capability of fish and inverte- 

 brates appear not to have been done. 



Shellfish, in addition to their significant contributions to the planktonic life 

 of marine ecosystems, are of special recreational and commercial' interest in 

 their adult form. That oil pollution is damaging to shellfisheries is becoming 

 well documented. Blumer, et al., (1970 p. 25), reports that the closure to taking 

 of shellfish — oysters, scallops, soft-shell clams and quahaugs — was maintained 

 into the second year following the West Falmouth spill. They note that the 

 presence or absence of an "oily smell" is no clue for presence of oil pollution 

 in shellfish or fish. 



Testimony by Dr. Clarence M. Tarzwell (U.S. Senate, 1971, p. 210) reported 

 a significant difference in sensitivity to oil between several si)ecies of mollu.-^cs 

 tested, with sca'lops being the most sensitive. Mortalities resulted from mechani- 

 cally dispersed oil as well as from crude oil floating on the surface of the 

 water. Oysters developed lesions in the vascular system at sublethal con- 

 centrations. 



The salmon resource is vulnerable to impact from oil pollution during most 

 life stages. Prior to hatching, the intact chorion, or outer covering, of salmon 

 eggs may present a barrier offering some protection against iwllutant hydro- 

 carbons. After hatching, however, the alevins become much more vulnerable 

 to invasion by dissolved substances passing through the relatively unprotected 

 wall of the attached yolk sac. Fat-.soluble hydrocarbons, such as the highly 

 toxic aromatics, could enter from the surrounding water to become concentrated 

 in the yolk and embryo at this time. That alevins, or .sac fry, are more sensitive 

 to some toxicants than eggs has been shown by Rice (1971) in experiments 

 with the effect of ammonia on rainbow trout. 



The food web of juvenile salmon during early life in estuarin^^ and nearshore 

 waters is critically dependent upon the environment and planktonic life of 

 these regions (Parsons and LeBrasseur, 1970). J. E. Bailey (Personal com- 

 munication by J. E. Bailey to D. Evans, 1071). studied and showed the dependency 

 of pink and chum salmon fry on food organisms of the nearshore and littoral 

 or intertidal regions of Southeast Alaska. A strong proportion of planktonic 

 forms of nearshore and littoral dependent organisms made up substantial amounts 

 of the food of these juvenile salmon. 



A significant cyclical estuarine photosynthetic production, characterized by 

 large increases in phytoplankton during the spring, occurs at the time of large 

 concentrations of fish in the estuarines (Copeland. 1971, p. 828). Biological 

 timing of an organism's life cycle with favorable conditions in the environment 

 is recognized in mnny animals (Andrewartha and Birch, 19r)4, p. 85, 525). 



Gunter (1961, p. 182) has pointed out the estuaries are nursery grounds and 

 refuges for young fishes. Even a temporary loss of phytoplankton and intertidal 

 and littoral invertebrate production due to an oil spill could have devastating 

 effects on other species if it occured at certain times and places. 



