Because we know so little about the movement 

 of deep currents, we cannot say to what extent 

 radioactive wastes deposited in the deep sea 

 might contaminate fish and plant life. Here, 

 a Japanese uses a Geiger counter to test 

 fish for radioactivity in a Tokyo market. 



about in the surface layers of the ocean. These algae, most of them 

 invisible to the naked eye, are the "grass" of the sea. They provide 

 the food for a host of small herbivorous, or plant-eating, plankton 

 animals which in turn provide food for small carnivorous creatures, 

 and eventually for fish and whales. At every stage of this food 

 chain - when one animal eats another — great amounts of organic 

 matter are lost, partly because animals are unable to assimilate all 

 they eat, and partly because much of their food is "wasted" through 

 respiration and excretion. So the fish we catch represent only a 

 small part of the original production of organic matter by photo- 

 synthesis. 



The quantity of plants or animals present in any place is always 

 changing as an animal eats a plant or one animal eats another. It is 

 only a momentary point of balance between the rates at which they 

 are produced and at which they are destroyed. So when we want to 

 compare the fertility of one part of the sea with another, we compare 

 their rates of production— either gross production (the rate of produc- 



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