Geographic Location 



Trophic Nature of the Lake 



Amounf , composition und distribution of 



pUnH and onirrMU. Abo 



ratot of circuUtion. 



'Productivity' 



Figure 7. A diagram showing the contributions toward lake productivity 

 by some interesting factors, both inside and outside of a body of water After 

 a diagram by D. S. Rawson. (By courtesy of the American Association for 

 the Advancement of Science. ) 



volved. For example, 'primary nutritive materials' depend on many 

 specific factors which are interrelated with and are governed by 

 'topography/ 'drainage area,' and the 'inflow of allocthonous mater- 

 ials.' The availability to plants of the 'primary nutrient materials,' 

 such as nitrogen, phosphorus, and various salts, would be, in part, 

 determined by 'oxygen concentration and utilization,' as well as by 

 the 'seasonal cycle of circulation and stagnation.' 'Depth' and 'wind' 

 together, or wind alone, directly affect turbidity ('transparency'), 



[35] 



