by man-made wastes that destroy organic life because the 

 water at times is not in sufficient volume to digest, neutralize, 

 and dissipate these wastes. 



Along the sea shores near the mouths of rivers is a border 

 of water less salty than that of the ocean, a border of balance 

 between ocean water and fresh water flowing from the land. 

 This border of balance is a habitat for fish of special value to 

 Man oysters, clams, lobsters, shrimps, and small fish. 



This value arises not alone from the unique flavor of these 

 fish, but also from the fact that they have an exceptional 

 capacity to transform mineral iodine, copper, magnesium, 

 and other health-giving minerals into forms easily assimilated 

 by the human body. 



These health-giving fish foods can exist only in the borders 

 of balance between salty and fresh water. This is because, 

 on the one hand, although they could live in the more salty 

 water, their principal enemies cannot live in the less salty 

 water; and on the other hand, because they thrive prin- 

 cipally on the organic life of the alluvial, under-water pastures 

 of soil and organic particles that are brought down to the 

 ocean by the fresh-water rivers. 



When the regularity of flow of these larger fresh-water 

 streams is seriously disturbed, as it may be when the regu- 

 larity of feeder flow from their headwaters is disturbed, the 

 balance of salinity of the less salty border is likewise dis- 

 turbed, with the result that the fish life peculiar to this 

 border tends to disappear. 



Balance in detail may be again illustrated by another 

 aspect of the importance of this border of less salty water. 

 On alluvial soils lying in the estuaries of rivers valuable food 

 plants may be grown truck gardening. This is because 

 the pressure of the fresh water flowing into the ocean pushes 

 the salty water away from the shore and prevents the salt 

 that would destroy the vegetable crops from seeping into 

 the alluvial estuary soils. Where fresh-water flow has 

 diminished and the pressure become reduced, as at the 

 mouth of the Sacramento River, valuable garden areas have 

 been destroyed by the seeping in of ocean salt. 



16 



