According to data published by the American 

 Petroleum Institute ( 1 949 ) , the first trace of color 

 that may be observed as a surface film on the sea 

 is formed by 100 gallons of oil spread over 1 

 square mile. Films of much darker colors may 

 indicate 1,332 gallons of oil per square mile. Ex- 

 periments conducted by the Committee" on the 

 Prevention of Pollution of the Seas (1953) showed 

 that 15 tons of oil covered an area of 8 square 

 miles. In 8 days, it had drifted about 20 miles 

 from the point of discharge. The same committee 

 (1953) indicated another source of oil pollution 

 that should not be neglected. It has been found that 

 unburned fuel oil escaping through the funnels of 

 oil-burning ships may comprise 1 to 2 percent of 

 the total oil consumed and it may be deposited on 

 the sea surface. British investigators attributed the 

 disappearance of eel grass (Zostera) to minute 

 quantities of oil. Oil weakens the plant and makes 

 it susceptible to attacks of a parasitic protozoan 

 (Labyrinthula) . Observations made several years 

 ago at Woods Hole showed that young Zostera 

 that began to reappear in local bays after several 

 years of absence were already infected by this 

 microorganism even though they appeared to be 

 healthy. 



Adsorption of Oil by Sand, Clay, Silt, and 

 Other Suspended Particles 



Oil of surface films is easily adsorbed on clay 

 particles and other suspended materials, forming 

 large and relatively heavy aggregates that sink to 

 the bottom. The surface of the water may appear 

 free from pollution, until the sediment is stirred by 

 wave action and the released oil floats up again. 



During World War II, a product known as 

 "carbonized sand" was manufactured for the U.S. 

 Navy and used for the primary purpose of rapidly 

 removing oil spilled or leaked from ships. Carbon- 

 ized sand was used principally as a rapid method 

 to prevent and stop fires. Sand and oil aggregates, 

 being much heavier than sea water, sank very 

 rapidly and remained on the bottom. Experimental 

 work has shown that the toxic effect of oils is not 

 diminished by this method (Chipman and Galts- 

 off, 1949). Since the end of World War II, a num- 

 ber of preparations to be used as solvents, emulsi- 

 fiers, and dispersing agents of oil slicks in harbor 

 v/aters appeared in New Zealand, Western Europe, 

 and the United States. These preparations are be- 

 ing offered under various trade names and their 

 chemical composition is not always stated. It is 

 often claimed that such compounds remove oil 

 slicks more efficiently than mopping with straw or 



coarse canvas fabric (skrim), a method exten- 

 sively used in Auckland Harbor (Chitty, 1948). 

 It is, however, generally recognized that various 

 detergents and emulsifiers are toxic to aquatic life 

 and therefore compound the danger of oil pollu- 

 tion. Mechanical means such as preventing the 

 spread of a slick by surroimding it with floating 

 barriers (plastic booms), spreading sawdust and 

 removing an oil aggregate by scooping or raking, 

 and erecting grass or straw barriers along the 

 beaches are probably more effective at present 

 than the chemical methods of dispersing or dis- 

 solving oil. Even anchoring oil by combining it 

 with relatively heavy carbonized sand seems to be 

 preferable to chemical methods. 



Toxicity of Crude Oil and Petroleum Products 



Oil may injure aquatic life by direct contact 

 with the organism, by poisoning with various water 

 soluble substances that may be leached from oil, 

 or by emulsions of oil which may smear the gills or 

 be swallowed with water and food. A heavy oil 

 film on the water surface may interfere with the 

 exchange of gases and respiration. 



A number of observations have been recorded 

 of the concentrations of oil in sea water which are 

 deleterious to various species. Experimental data, 

 however, are scarce and consequently the toxicol- 

 ogy of oil to marine organisms is not well under- 

 stood. 



Nelson (1925) observed marine mollusks (Mya 

 arenaria) being destroyed by oil on tidal flats of 

 Staten Island, N.Y. The Pacific coast sea urchin, 

 Strongylocentrotus purpuratus, dies in about 1 

 hour in a 0.1 percent emulsion of diesel oil. After 

 20 to 40 minutes in this concentration the animals 

 fail to cling to the bottom and may be washed 

 away (North, et al, 1964). 



Crude oil absorbed by carbonized sand does not 

 lose its toxicity. This has been shown by laboratory 

 experiments conducted at Woods Hole (Chipman 

 and Galtsoff , 1 949 ) . The amount of oil used was 

 limited to the quantity held in the sand, hence no 

 free oil was present in the water. The oil-sand 

 aggregates were placed in containers filled with sea 

 water but never came into contact with the test 

 animals. Four species were bioassayed: the very 

 hardy toadfish {Opsanus tau) in the yolk sac 

 stage, the moderately tolerant barnacle (Balanus 

 balanoides), and oyster (Crassostrea virginica), 

 and the extremely sensitive hydrozoan, (Tubularia 

 croced). 



The survival of toadfish embryos was indirectly 

 proportional to the concentration of oil in water. 



72 



