42 



REDFIELD, KETCHUM AND RICHARDS 



Table VI 



|f'HAP. 2 



Comparison of the Excess Oxygen Available in Deep Water of the Oceans 



(mg atoms /m 3 ) 



may be seen that with this allowance the deep water of the North Atlantic should 

 contain 81% of its original oxygen content and the Pacific about 44%. These 

 estimates approximate the magnitudes actually observed. 



These estimates only take account of the oxidation of organic matter which 

 is carried to depth with the movement of the water. Organic matter which 

 sinks from the euphotic zone to depth before decomposing creates an additional 

 demand on the oxygen supply. This effect is important at intermediate depths 

 and contributes to the formation of the oxygen minimum layer. In the Pacific 

 large areas exist at such depths where the oxygen is very nearly exhausted. 



The margin of safety against the development of anoxic conditions in the 

 deep ocean is not large. It depends on the limited quantities of nutrients 

 present in ocean water and the incomplete absorption of these elements from 

 the water during its circulation through the euphotic zone. 



D. Anoxic Conditions 



Where the accumulation of organic matter is great, the oxygen dissolved in 

 the water becomes completely exhausted, leading to a condition variously 

 designated as anaerobic, anaeric or anoxic. Under this condition, the oxidation 

 of organic matter continues by means of anaerobic bacterial processes in which 

 sulfate, nitrate, nitrite and carbon dioxide serve as hydrogen acceptors. The 

 reduced products of these substances accumulate in the water in addition to 

 the products of the oxidation of the organic matter. The result is to modify 

 the proportions of the components of the water in ways which differ from 

 those characteristic of regeneration in the presence of free oxygen. 



The principal reactions taking place in the presence and in the absence of 

 oxygen may be formally represented by the following equations, in which 



