DISCUSSION 



The ocean in the area where these studies were conducted 

 may be described as consisting of two water masses^ one 

 above the thermocline and one below. The thermocline 

 serves as a water-mass boundary. The turbidity structure 

 of the water depends on the turbidity of the two water masses 

 and their movements. 



It may be seen that on some days, such as 19-20 July 

 196 (fig. 10), the water mass above the thermocline is 

 relatively clear whereas the water below the thermocline 

 is turbid. On other days, such as 2-3 and 4-5 August 1960 

 (figs. 11 and 12), a turbidity layer occurs in or near the 

 water-mass boundary. There is a tendency for the turbidity 

 to appear in patches. Possibly interaction of the water 

 masses at the thermocline provides conditions that at the 

 moment are favorable for living organisms. On the other 

 hand, the organisms that make the water turbid commonly 

 have a particular density. Seeking a level at which their 

 buoyancy becomes neutral, they may float on the density 

 boundary of the thermocline, as appears to be the case in 

 figures 11 and 12. 



The vertical fluctuations of the turbidity can be accounted 

 for to a large extent by the presence of internal waves. These 

 waves contribute to the "patchy" pattern that occurs near the 

 thermocline. In view of the "patchiness, " a geographic curve 

 of single observations may be misleading. 



SUMMARY AND CONCLUSIONS 



The studies described in this report were conducted to 

 investigate the widely observed differences in the transpar- 

 ency of ocean water. Light transparency was measured by 

 means of a hydrophotometer. The data were recorded in 

 such a way as to relate turbidity to time, temperature, and 

 biological aspects. 



Vertical runs through the water column were made with 

 the hydrophotometer every half-hour. These were conducted 

 during four extended periods, one about 10 hours long and 

 three of 27 to 29 hours in duration. It was found that certain 

 relations existed between temperature structure, internal 

 waves, and turbidity. The level of higher turbidity gradients 



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