Factors affecting the survival of bacteria in sea water.

During recent years, the use of marine outfalls for the disposal of sanitary and industrial wastes has increased greatly and information regarding the fate of bacteria in sea water has assumed public health significance. Unpolluted sea water does not contain large numbers of bacteria, and bacteria which enterthe oceans by way of land drainage and sewage outfalls die quickly. The numbers of bacteria in sea water are determined by those factors which influence growth and reproduction as well as by those that control survival and cause death. General aspects of the survival of bacteria in sea water were discussed by Ketchum (1953), Harvey (1957), and Wood (1958). The subject was considered in detail by ZoBell (1946), Greenberg (1956), and Orlob, (1956). Waksman and Hotchkiss (1937) suggested that the paucity of bacteria in sea water may be the result of any one or combination of various inter-related physicochemical and biological factors including: (a) the adsorption of bacteria and their sedimentation; (b) the destructive action of sunlight; (c) the lack of required nutrients; (d) the presence in sea water of toxic substances; (e) the presence of bacteriophages; (f) the utilization of bacteria as food by protozoa and other predators; and (g) the competitive and antagonistic effects of other microorganisms. These possibilities provide a convenient framework within which knowledge of the influence of various factors on the survival of bacteria in sea water can be reviewed.