34 



on June 19, the temperature on the bottom was 52° and at the 

 surface,, 64 .,5°, a spread of 14.5°F. 



Salinity 



Except in the immediate vicinity of the boil, surface 

 salinities were normal on all days of increased plankton 

 growth around Orange County and Hyperion outfalls. Near 

 Whites Point p lower salinities during the winter months 

 are attributable to surface drainage following moderate 

 rainfall o Subsurface salinities were also normal, except 

 near Whites Point where isothermal layers and rain runoff 

 caused mild variations o 



Water Transparency 



There was no tmusnaal discoloration of the surface waters 

 near the three outfalls during the winter months, even though 

 the recovered plankton samples were rust or reddish-brown in 

 color. During May and June, a tinge of brown could be detected 

 when high plankton numbers were present. This discoloration 

 was slight and not visible to some observers. Surface trans- 

 parencies frequently gave a Secchi disc reading of 20 to 25 

 feet, and at Orange County, 30 to 35 feet. Such transparencies 

 were, of course, present outside the sewage field. Within 

 the field typical readings of 4 to 10 feet were obtained. 



Subsurface transparencies taken with the hydrophotometer 

 were typical, except at Orange County on December 19 and 20, 

 1955. On these two days, a distinct subsurface layer of low 

 light transmission occurred and is attributed to the concen- 

 tration of plankton (Figure 12). On the 19th, the layer 



