Marine Bacteriology and the Problem of Mineralization 55 



some means is devised to show the occurrence of the process in 

 situ. 



Turning from specific processes to the overall quantitative 

 aspects of mineralization, we again find that marine bacteriology 

 has provided little information of xalue. In the discussion of this 

 point I will substitute the term regeneration for mineralization 

 since it cannot be implied that complete mineralization of organic 

 matter takes place or is necessary. 



Regeneration and productivity are of course intimately re- 

 lated and in a steady state system, must be in balance. A great 

 deal of experimentation has been carried out in an effort to ar- 

 rive at a value for the productivity of the oceans, and although 

 the various estimates do not completely agree, a reasonable value 

 that is probably not in error by as much as a magnitude may be 

 assumed. A value of 150 gm of carbon assimilated annually per 

 square meter was chosen to calculate the budget mentioned ear- 

 lier which is intermediate between the estimates of Trask (25) 

 and Riley ( 18) on the one hand and that of Steeman-Nielsen (24) 

 on the other. Assuming that the standing crop of cellular matter 

 is reasonablv constant then the above value may also be taken 

 for the annual regeneration of carbon. The questions arise as 

 to where the regeneration takes place and to what extent bacterial 

 processes are involved. 



Based on the distribution of oxygen, phosphate and nitrate in 

 the Atlantic Ocean, Riley (19) estimated that 90 per cent of the 

 organic matter formed is utilized in the upper 200 meters of 

 water, most of the remainder being regenerated in the deep water 

 and sediments. In terms of rate, this represents the regeneration of 

 about 0.1 /'g carbon per liour per liter of water in the 

 upper 200 meters. Assuming that the organic carbon is 

 oxidized to COl-, the corresponding oxygen demand is 0.25 

 fxg per liter per hour. Using ZoBell's (31) estimate of 

 2 X 10~^ /'g oxygen consumed per cell per hour, a steady state 

 bacterial population of over 10'^ cells per liter would be required 

 if the bacteria were exclusively responsible for mineralization. 



This required quantity of bacteria is far out of line with cur- 

 rent estimates of average bacterial populations in the upper 200 



