286 E. Steemann Nielsen 



surface water from the Sargasso Sea varies from 0-12 to 0-51 ml O2 consumed per 1. 

 There is no reason to beUeve that the content of organic matter in the surface water 

 of this rather uniform sea should vary much from place to place. It is more Hkely 

 that the amount of antibiotics present in the water at the time it is collected varies 

 somewhat from place to place. The time of the day for the collection may be rather 

 important, too. Near sunset the concentration of antibiotics is possibly higher than 

 near sunrise. 



It is at present impossible to state if non-autotrophic organisms independent of 

 light secrete antibiotics. This is by no means unbeUevable. Some observations on the 

 Galathea expedition support this possibility. A verification is, however, needed. 



Krogh (1934) — as he explained it himself — offered a vague suggestion that the 

 animal hfe at great depths in the oceans depends on bacteria. At that time he knew 

 the concentration of soluble organic matter in ocean water. He knew, too, that this 

 organic matter normally was not decomposed by bacteria. He did not, however, 

 know that a material part of this organic matter is easily decomposed if solid surfaces 

 are present. At the sea bottom such soHd surfaces are present. A rather considerable 

 decomposition of this organic matter is apparently going on here constantly. Most 

 of the " old " organic matter diluted in sea water is most likely ultimately decomposed 

 at the sea bottom. The bacteria living on this matter present most Hkely a very 

 important, although not the only food source for the bottom animals at very great 

 depths. 



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