54 Marine Microbiology 



biochemist with his credo of comparative biochemistry and his 

 respect for the precision of nature in performing biosynthesis, 

 unless alternative ways out of the dilemma are presented, a 

 search for such a biochemical mechanism would make sense for 

 a marine microbiologist. 



Actually, we are not yet forced into an examination of the 

 heresies suggested above. Reasoning that metabolically released 

 nitrogen might have a different isotopic composition than atmos- 

 pheric nitrogen with which the ocean nitrogen is in equilibrium, 

 Richards and Benson (17) measured the N^V^^^ ratios of the 

 molecular nitrogen present in the anaerobic waters of the Cariaco 

 Trench and in the open ocean outside. The great difference in the 

 ratios led them to conclude that denitrification is an active 

 process in the Cariaco Trench. 



The significance of this outstanding contribution is several 

 fold. In the first place, it provides a tool whereby the marine 

 microbiologist, who should also be a chemical oceanographer of 

 sorts, can look for dentrification in situ. Secondly, it delineates a 

 type of area where the search for, and the description of, denitri- 

 fying bacteria would be meaningful for marine microbiology. It 

 should not be inferred that the findings of Richards and Benson 

 answers the dilemma posed by the nitrogen balance. Actually 

 it presents the marine microbiologist with a third chore, the 

 development of some method that will measure the in situ rate of 

 denitrification in environments like the Cariaco Trench. This is 

 the most difficult task of all, but only when it is accomplished 

 will marine microbiology know whether the books are balanced 

 or whether viewpoints that might currently be considered here- 

 sies must be brought into a state respectability. 



The mention of denitrification almost automatically brings 

 into focus the counterprocess of nitrogen fixation. To the extent 

 that this process occurs, the nitrogen budget of the oceans would 

 be thrown further out of balance. This in itself does not rule out 

 nitrogen fixation as being significant in the marine environment. 

 It does point out, however, that the demonstration of potential 

 nitrogen fixing organisms in the marine microflora has essentially 

 no significance to marine microbiology unless at the same time 



