Table 4. -Estimation of dissolved oxygen supersaturation from photosynthesis using 

 nutrient utilizations. 



1. Estimated initial PO4 concentration =1.01 /L/g-at/1 



2. Estimated initial NO3 concentration = 6.0 /:/g-at/l 



3. Estimated initial O2 concentration = 7.95 ml/1 



4. Estimated PO4 utilization = 1.01 - 0.59 Mg-at/1 = 0.42 jug-at/1 



5. Estimated NO3 utilization = 6.0 - 0.3 /ig-at/l = 5.7 Mg-at/l 



6. O2 added based on PO4 utilization = 0.42 Mg-at/1 x 27 = 115.92 /ig-at/l = 1.29 ml/1 



7. O2 added based on NO3 utilization = 5.7A(g-at/l x 17.2 = 98.04 Mg-at/1 = 1.09 ml/1 



7.95 + 1.29 



8. Supersaturation based on PO4 utilization ■ 



7.95 



xl00= 116% 



7.95 + 1.09 



9. Supersaturation based on NOo utilization x 100 = 113% 



^ •* 7.95 



*A0;AN:AP = 276:16:1 



nutrient concentrations were based on values 

 from WEBSEC-71 samples taken at the oxygen 

 maximum. The ratios of change of oxygen and 

 nutrients determined by Redfield, Ketchum and 

 Richards (1963) were used. The estimated values 

 of oxygen saturation, 116% (PO4) and 113% 

 (NO3) (table 4) fit closely the observed saturation 

 values (120%) at 15 meters from WEBSEC-71. 

 The small difference between the estimated and 

 observed values are probably due to errors in the 

 assumptions. However, it is evident that photo- 

 synthesis can cause considerable oxygen satura- 

 tions of these waters. 



There is the possibility that the high supersat- 

 uration values are from earlier photosynthetic ac- 

 tivity rather than fiom present activity. Sverdrup 

 (1929) found high oxygen supersaturations in the 

 eastern Arctic and attributed them to ice cover 

 preventing photosynthetically produced oxygen 

 from escaping to the atmosphere. This 

 mechanism is probably important in the early 

 summer when a thin ice cover may be present. 

 The highly photosynthetically oxygenated water 

 would then sink to deeper depths with the oneset 



of heavy icemelt (which forms a dilute surface 

 layer). The poor mixing in the area would help in 

 maintaining the subsurface oxygen maximum. 

 The formation of the summer pycnocline would 

 also help to maintain the layer. The observed 

 maximum values during WEBSEC-71 were usu- 

 ally at or below the strong pycnocline. Since 

 stability reduces vertical eddy diffusion and hy- 

 drostatic pressure (though small) increases ox- 

 ygen solubility, the condition of the observed high 

 values of saturation being below the pycnocline 

 favors the retention of oxygen. 



Other mechanisms were studied to determine if 

 they might account for the observed supersatura- 

 tions. Mixing of any of the water masses present in 

 equal parts would give saturation values only up 

 to 101%. In situ warming even up to 3°C could not 

 cause saturations greater than 106%. The ob- 

 served saturations are not entirely due to sea-air 

 interchange because the surface water should 

 equilibrate with the atmosphere quickly. Also, 

 the observed supersaturations are associated with 

 higher salinity water ( >27°/oo) than found at the 

 surface. 



14 



