usually fell on or just below the maximum temperature 



gradient. The most turbid water was frequently found on 



the thermocline which moves up and down with internal waves. 



Long-period changes in the depth of turbidity maxima 

 followed closely the changes in the level of the thermocline 

 (which has a tidal cycle), but short-period changes could not 

 be explained in this manner. Turbidity was found to be caused 

 principally by concentrations of living plankton and detritus 

 or decayed plankton. 



RECOMMENDATIONS 



1. For continuous studies of several days' duration, 

 several hydrophotometers should be assembled in a string 

 and the data indicated by some type of multichannel recorder. 

 It would be desirable to use for this purpose either an inter- 

 polating contour recorder which would automatically print 

 turbidity isolines, or a digital system which would punch 



the information on computer tapes. 



2. Further turbidity studies should be conducted at the 

 NEL tower, and as before should be supported by temperature 

 and biological studies. 



3. Additional data should be obtained in other geographi- 

 cal areas for comparison with the data from Mission Beach, 



4. Acoustical-biological -turbidity relations should be 

 studied in more detail to determine the cause of patchiness 

 in the distribution of acoustic scatterers. Use should be 

 made of a high-frequency sea scanner that can be tilted to 

 delineate the size and shape of scattering patches. 



25 



