ZoBell — 1 10 — Marine Microbiology 



the bottom of Walvis Bay on the South African Coast depleted the oxygen 

 from the overlying water, and at times has been lethal to the fauna and 

 flora. Mears (1943) relates that in certain polluted harbors (notably 

 Calloa, Peru) so much H2S is produced that metalhc surfaces and surfaces 

 coated with lead-base paints are blackened by the formation of metallic 

 sulfides, giving rise to the phenomenon known in nautical parlance as the 

 "Calloa Painter." 



From his investigations on the "stinking putrefaction" in the Little 

 Kiel, Germany, during summer, Baier (1935) concluded, that while the 

 production of appreciable quantities of H2S corresponded with periods 

 during which there was much organic matter undergoing decomposition, 

 the H2S was derived primarily from the bacterial reduction of sulfate and 

 only to a slight extent from proteins. Most if not all of the H2S was gen- 

 erated in the bottom mud. 



Autotrophic bacteria may be instrumental in the oxidation of H2S, 

 methane, carbon monoxide, and hydrogen at the mud-water interface or 

 in the overlying water, provided that there is an adequate supply of dis- 

 solved oxygen. 



Effect on organic content of bottom deposits : — Bacteria influence the 

 quality and quantity of organic matter, both during the time that it is 

 settling to the bottom and after it has been deposited and buried. The 

 organic compounds which are most susceptible to attack, such as simple 

 proteins and carbohydrates, are utilized first, leaving the more refractory 

 compounds such as lignins, complex proteins, chitins, lipids, polyuronides, 

 and other complexes known collectively as humus. This occurs in marine 

 bottom deposits (Waksman, 1933 ; Trask, 1939) as well as in lakes (Waks- 

 MAN, 1941a). 



Illustrative data are provided by Waksman and Hotchkiss (1937) 

 who found the biochemical oxygen demand (B.O.D.) of mud from differ- 

 ent depths as follows: 



The B.O.D. is the amount of oxygen consumed by bacteria in oxidizing 

 organic matter in a given period of time. Thus the B.O.D. is partly a 

 measure of the quantity of organic matter and partly a measure of its 

 biological oxidizability. 



Anderson (1940) determined the organic content of a large number of 

 marine muds and also their B.O.D. In general, the largest organic con- 

 tent, as well as the highest 15-day B.O.D. per gram of organic carbon, was 

 found in the topmost sections of the cores, although many unexplainable 

 irregularities are reported. As a rule, the surface layers of mud contain 

 the most organic matter, and that which is present is more readily decom- 

 posed by bacteria than the organic matter at greater depths in the cores. 

 In representative experiments conducted by Anderson (1940), the 

 B.O.D. of samples was 1.39 ml. during the first 5 days, 0.27 ml. during the 

 second five days, and 0.24 ml. during the third 5 days, thereby showing 

 a progressive decrease in the oxidizability of the organic matter. 



Detailed analyses of cores from the southern California region by 

 MoBERG et al. (1937) showed that the highest organic content is at the 



