Using a computer, we may now calculate N. The 

 number of organisms per unit volume of water can be cal- 

 culated by dividing N by the volume of the light beams. 

 Figure 9 illustrates the theoretical curves (100-percent 

 cell number) derived from the foregoing computations. In 

 this treatment the assumption has been made that Gymnodinium 

 flavum was the only light absorber, whereas this organism 

 comprised about 65 percent of total microconstituents. 

 Therefore, the curve for 65 percent of the theoretical 100- 

 percent cell number is also shown for comparison with the 

 plotted Gymnodinium flavum transparency data (fig. 9A). 



Figure 9. Theoretical relationship between light attenuation and number of microentities 

 as determined by a mathematical model for predicting population densities by light 

 attenuation. A. Gymnodinium flavum, Operation I, B. Gymnodinium flavum, Operation II, 

 C. Total microconstituents. Operation I, D. Total microconstituents. Operation II. 



24 



