Chapter 53 



Suppression of Bacterial Growth by Sea Water* 



Galen E. Jones 

 INTRODUCTION 



T 



he populations of viable bacteria in the sea range from 10^ to 

 10® cells per ml ( 21, 22 ) , and are usually less than 10^ per ml of 

 open ocean water, particularly in high latitudes (4, 7 ) . However, 

 the natural organic matter in sea water will support considerably 

 larger populations, as is indicated by bacterial proliferation in 

 sea- water samples kept in clean containers for a few days (23). 

 These observations suggest that bacterial populations in the ocean 

 are limited by a factor or factors other than the energy source. 



There is abundant evidence that viable bacteria which enter 

 the oceans from land drainage and sewage outfalls are soon 

 drastically reduced in numbers (2, 3, 11). Pramer, Carlucci, and 

 Scarpino (13) attribute greater bactericidal significance to 

 physico-chemical than to biological factors in sea water. 



The dynamic nature of physical, chemical, and biological 

 balances in the sea was emphasized by the external metabolite 

 theory of Lucas ( 8 ) , who proposed that organisms may influence 

 the activities of other living things by producing essential micro- 

 nutrients, by removing inhibitory compounds, or by excreting 

 inhibitory substances. There are now numerous indications that 

 both stimulatoiy and inhibitory organic compounds are present 

 in sea water (1, 5, 6, 17, 18); see also reviews by Vallentyne (19), 

 Saunders (15), Provasoli et al. (14). 



The pui^pose of this investigation was to obtain direct evi- 

 dence for the eff^ect of sea water from different sources on the 

 growth of certain freshwater and marine bacteria. Previous in- 

 vestigators have studied mortality of pollution bacteria in sea 



Contribution from the Scripps Institution of Oceanography. 



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