52 Marine Microbiology 



major site of nitrification. The calculations of Gunnerson (12) 

 based on chemical analyses of water in Santa Monica Bay, not 

 only support the thesis that active nitrification is occurring in 

 the water but also provide a magnitude for the process in the 

 area stucUed. It must be admitted that the data on which the 

 calculations are based could be more extensive, and also that 

 the environment involved is not a normal marine area because of 

 the massive discharge of domestic sewage received. Nevertheless, 

 areas such as the Santa Monica Bav which are numerous all over 

 the world, deserve the attention of marine bacteriologists be- 

 cause the normal mineralization processes must be accentuated 

 therein. They provide in situ experimental situations amenable to 

 direct investigation by the microbiologist. The demonstration of 

 nitrifying organisms, either of the classical soil type or of distinct 

 new types, whose distribution decreases outward from the point 

 source of the substrate, the sewage outfall, in a manner consistent 

 with the distribution of ammonia and nitrate around the outfall, 

 would be, I believe, a contribution to marine microbiology in the 

 sense that Winogradsky would have approved. 



Returning to the problem of denitrification, mentioned ear- 

 her, available oceanographic data suggests that profitable micro- 

 biological work remains to be done. Some six years ago my col- 

 leagues and 1(6) attempted to draw up budgets for three major 

 nutrients in the oceans, nitrogen, phosphorus and silicon. Our 

 results are briefly summarized in Table I. Considering the un- 

 certainties in the data available, we were agreeably surprised 

 to find that a reasonable balance was obtained between the 

 phosphorous and silicon input from the land and the loss to the 

 marine sediments, as should be the situation if the oceans are 

 in a steady state condition. However, the same was not true for 

 the nitrogen calculation which showed an excess input of about 

 7 X 10' metric tons per year. To balance the budget, we had 

 to postulate denitrification as a mechanism for the escape of ni- 

 trogen from the sea. Assuming denitrification to be exclusively an 

 anaerobic process (see for example, Skerman and MacRae, 23), 

 one would think first of the sediments of high organic content, 

 such as those of tlie neritic basins and estuaries, as its site. How- 

 ever, calculations based on the decrease of nitrogen with depth 



