NATURAL SLICKS IN THE PACIFIC AND ANTARCTIC OCEANS 



Natural slicks are glassy patches or streaks upon the 

 surface of the ocean that give it a heterogeneous aspect insofar 

 as the reflection of light is concerned. Prior to departure 

 on Operation HIGHJUMP, it was decided to observe the distri- 

 bution of these features. They have apparently received 

 little previous attention, for there is little information about 

 natural slicks in oceanographic literature. 



It is known that the natural slicks are commonly referred 

 to by fishermen and mariners as streaks where the wind is 

 not striking the sea surface. Also, sailboats frequently avoid 

 these areas of supposed calm. Yet, a few simple observations, 

 such as watching the slicks drifting slowly with the current, 

 show that the theory that they are produced by the wind is 

 untenable. They are discussed in the biological section of 

 this report in the belief that they are thin films of natural 

 oil from organisms, especially diatoms; thus in a sense they 

 are presumably a biological phenomenon. The fact that 

 diatoms synthesize droplets of oil in their cells to provide 

 a food reserve and also to assist them in keeping afloat is 

 well known (Sverdrup, Johnson, and Fleming;4 Cupp-* 1 ). 

 Upon their destruction, it is probable that these droplets of 

 oil rise to the surface and that they then tend to spread into 

 a monomolecular layer, thus producing slicks. Of course 

 other marine animals may also contribute oil to form natural 

 slicks but they are probably quantitatively unimportant as 

 compared to diatoms. In any case, much of their oil results 

 from grazing upon the diatoms. 



If slicks are films of natural oils, one would expect them 

 to be the most prominently developed in regions of high 

 organic production, as in coastal waters and near islands 

 where upwelling occurs. With this in mind, daily observations 

 were made during Operation HIGHJUMP and such a distribution 

 was found actually to exist. 



Upon the departure of the ships from California on 2 De- 

 cember 1946, it was noted that slicks were developed rather 

 prominently in the green coastal waters but that when the blue 

 oceanic waters were reached the slicks had disappeared 

 altogether. When the ships passed the Marquesas Islands, 

 the only landfall en route to the antarctic, a slight develop- 

 ment of slicks was noted. Although as a general rule slicks 

 were not noted in oceanic water, on 15 December in the 

 South Pacific (latitude 30°48'S, longitude 152°24'W), with 

 smooth sea conditions prevailing, some slicks were found 

 that were just faintly discernible. 



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