33 



Both methods are necessary parts of a complete survey. 



Additional data were available from surf temperature 

 reports of the Los Angeles County Life Guard Station at Venice, 

 and from similar records of the U. S. Coast and Geodetic Survey 

 at Santa Monica Harbor. For adjacent offshore areas, tempera- 

 tures and salinities at various depths have been taken by the 

 Scripps Institution of Oceanography, but their stations in most 

 cases were located outside the area of the present investigation,, 

 The staff of the Los Angeles City Bureau of Sanitation also 

 has collected data in the bay which are tabulated in the reports 

 of that organization. 



Thermoclines and Gradients 



For the purposes of this report, thermoclines and gradients 

 have been separated on the basis of their characteristic 

 appearance in bathythermograms. In general, if a temperature 

 curve changes abruptly in slope below a nearly isothermal sur- 

 face layer, thus forming a sharp discontinuity or boundary, and 

 the difference in temperature is relatively large, it has been 

 termed a thermocline. A smooth or even an intermittent change, 

 but without a marked break at any depth has been termed a 

 thermal gradient. While this is a rough, qualitative distinction, 

 it is adequate for the purpose at hand. 



Thermoclines and gradients were best developed when the 

 surface waters were warmed in the spring and summer. They were 

 least prominent during the late fall and winter months when 

 surface temperatures were reduced. 



