54 



REDFIELD, KETCHUM AND RICHARDS 



[CHAP. 2 



in which AQn/At is the rate of change in quantity due to biological activity and 

 AQs/At is the rate at which oxygen is exchanged with the atmosphere across 

 the sea surface. AQo/At was obtained from hydrographic data by integrating 

 the quantity of dissolved oxygen underlying a square meter of sea surface to a 

 depth of 200 m (below which the changes in oxygen concentration were negli- 

 gible) at two periods separated by the interval At and taking the difference. 

 AQrJAI was obtained by a similar integration of the inorganic phosphorus 

 concentration, and multiplying the result by the oxidative ratio of phosphorus. 

 If concentrations are expressed in mg atoms, AQRJAt= —276 AP/At. The mean 

 rate of diffusion of oxygen across the sea surface, AQs/At, was obtained by 

 introducing these measurements into equation (3). 



The results of the study are illustrated in Fig. 9. During the winter period 

 oxygen entered the water at a greater rate than it was reduced by organic 

 activity. As a result the quantity of oxygen in the water column increased. 



+ 10 



o 



-10 

 -20 



- A0 /At 



+20 

 + 10 

 

 -10 

 -20 

 -30 

 -40 

 -50 



— ■ 



- A0 £ /At 



A0 R /At 



+ 50 



+40 



♦30 

 + 20 

 + 10 

 



-10 

 -20 



JASONDJFMAMJJA 



Fig. 9. Seasonal cycle in change in oxygen content of water of Gulf of Maine. AQo/At, 

 rate of change of oxygen content of water column ; AQujAt, rate of change attributed 

 to biological activity ; AQg/At, rate of change attributed to diffusion across sea 

 surface. Ordinates : rate of change in units of 10 4 ml per m 2 x months. Abscissa : time 

 in months. (Recalculated from data of Redfield, 1948, using oxidative ratio AOj 

 AP= -276.) 



This was possible because of the increased solubility which accompanied the 

 cooling of the water. In the spring, when the growth of phytoplankton is 

 intense, oxygen was produced more rapidly than it was reduced by organic 

 activity. Oxygen escaped to the atmosphere at a nearly equivalent rate during 



