Figure 11 shows the vertical distribution of dissolved oxygen with depth 

 between stations 5 and 27 (32° W . and 4° N . along the 78° E . meridian) . The 

 most striking feature of this profile is the large mass of low oxygen water in the 

 north which came in from the Arabian Sea and, to a lesser extent, from the Red 

 Sea. To the south of the profile, this water pushed the high oxygen water upwards, 

 Mixture of the two is clearly shown . The disturbed condition between 10° and 

 18° S . is also shown as in the salinity profile for the same stations . 



In Figures 20,21, and 22, the vertical distribution of dissolved oxygen at 

 selected stations along this south -north section is shown. The effect of the large 

 body of low oxygen water is evident from the highly irregular form of the curve. 



Figure 17 shows the vertical distribution of dissolved oxygen between stations 

 27 and 30. In the zone of turbulence, oxygen values were average, but below 

 this depth values decreased rapidly. At station 28, the lowest values were observ- 

 ed. The lowest, 0.39 ml/I, occurred at 250 meters depth. Below a depth of 

 from between 1000 and 1200 meters, where the 1 .00 ml/I isopleth is shown in this 

 profile, oxygen values increased steadily toward the bottom of the casts. 



In Figure 22 B, C, and D, the vertical distribution of dissolved oxygen is 

 shown for stations 27, 28, and 30. The very low oxygen values observed at 

 station 28 again stand out in the peculiarly shaped curve. Station 30 shows an 

 entirely different type of oxygen curve as values decrease very rapidly below 

 the zone of turbulence In the layer between 100 and 200 meters, and then re- 

 main almost without change from this depth to the bottom. 



F . Percentage of Saturation of Dissolved Oxygen 



Supplementing a knowledge of the actual values of dissolved oxygen in 

 oceanic waters, it is of interest to know just how much oxygen is dissolved in 

 comparison with the amount the water could hold under standard pressure at the 

 temperature observed. Percentages of saturation less than maximum (100%) invite 

 questions as to why the water is not saturated, and these questions are not always 

 easy to answer. Temperature is involved because cold water will hold more dis- 

 solved gas than warm water. Currents which bring water of low or high oxygen 

 from other regions often account for high or low saturation percentages. Abun- 

 dance or scarcity of phytoplankton or a superabundance of oxygen consuming 

 plankton are factors to be taken into consideration. When favorable conditions 

 prevail such as calm, clear weather, bright sunshine, and abundant phytoplankton, 

 supersaturation In the upper waters may result. With a transparent, snowless Ice 

 cover, percentages of supersaturation as high as 300% have been noted In Inland 

 lakes . 



Figures 6, 12, and 18, show vertical distribution of percentage of saturation 



39 



