THE OCEAN FEEDING-GROUNDS 97 



quantity of plankton, according to M. Nathansohn, 

 depends solely upon the dynamic equilibrium of two 

 antagonistic processes : the production of algae and 

 their destruction by physical and animal agencies. The 

 physical agencies are of various kinds : excessive or 

 defective salinity of the water, too high or too low a 

 temperature, &c. As for the animals, they may be 

 large or small, but all the small animals, and without 

 exception all fry or larvae, feed upon plankton, and we 

 may at once assert that those regions which are richest 

 in plankton, and especially in vegetable plankton, at the 

 moment of spawning, are also the richest in fish. 



It is not only the soluble salts which are absorbed 

 by vegetable plankton in order to fabricate living matter ; 

 the whole series of mineral substances are also required, 

 of which the most important are the inorganic azotic 

 compounds. These latter (nitrites, nitrates, and 

 ammonia) derive almost entirely from the putrefaction 

 of the albuminoid matters furnished by the animal 

 and vegetable series themselves during their life or 

 after their death. The process is extremely pretty. It 

 is carried out by the nitrifying bacteria. By the aid of 

 oxygen they transform the ammonia into nitric and 

 nitrous acid. But the azotic products, soluble in water 

 and incessantly washed into the sea, century after century, 

 by the rivers and the rains, would finally poison the 

 water and render life in the ocean impossible. Brandt, 

 whom I cite as quoted by Pruv6t, has demonstrated, by a 

 calculation based upon the alluvia of the Rhine, that the 

 total mass of oceanic waters must receive from the rivers 

 an annual contribution of azote which is not less than 

 i gramme per 33,000 cubic metres, or 3 grammes 

 per cubic metre in 100,000 years, or 30 grammes in a 

 million years. From this one can see that the ocean no 



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