Marine Bacteriology and the Problem of Mineralization 57 



used by the phytoplankton and if respiration of marine nitrifiers 

 proceeded at tlie previously assumed rate of 2 X 10~^ /xg O2 per 

 cell per hour, then a standing crop of nitrifiers of more than 10^ 

 cells per liter is required. As previously mentioned, standard 

 enrichment procedures as borrowed from soil microbiology usu- 

 ally fail to detect any nitrifiers at all in the ocean waters. 



The existing lack of information about nitrification allows 

 ample room for speculation. One can postulate inadequate tech- 

 niques or nitrifiers of an undetected nature; one can postulate 

 that the bulk of the nitrogen is only ammonified before reuse; 

 or one can even postulate that a significant portion of the nitrogen 

 is not mineralized at all but is reused by the plankton in the 

 fonii of soluble organic nitrogen. It would be possible to sup- 

 port all of the postulates above by reference to results of labora- 

 tory investigations (see for example papers by Watson (27), 

 Guillard (11), and Pintner and Provasoli (16), this symposium) 

 but a quantitative assessment of their significance is not possible. 

 It is obvious, however, that we are not yet privileged to assume 

 for the oceans the same cycle of nitrogen as in soil. 



In light of the material presented, it seems fair to say that 

 few of the oceanographically intelligible questions that might be 

 asked of a marine microbiologist about mineralization seem 

 answerable at this time. Thus, perhaps, it was not so presumptu- 

 ous to pose the question that opened this paper. Unlike Wino- 

 gradsky, however, I have no methodology to present that is com- 

 pletely adequate to remedy the situation. It is my feeling that 

 in situ studies are necessary. For such studies more than the lab- 

 oratory techniques of bacteriology are needed: knowledge of 

 oceanography, sedimentology, chemistry and biochemistiy must 

 also be applied. 



It is much simpler to deal with marine sediments than with 

 sea water. This is perhaps why most of the contributions to the 

 mineralization session of this symposium were concerned with 

 microbial acti\ity in sedimentary material. There are several rea- 

 sons wh\^ this should be so, among the most important being that 

 in general, once deposited, sediments sta\' put. Applying the 

 steady state generalization to a sediment, one has onlv to measure 

 the change of some parameter with depth in a sediment to have 



