saturated. This is in marked contrast to the findings of the 

 Australians at Mawson (Bunt, 1960) where saturated or supersaturated 

 (as high as 171%) water was a common occurrence. Their stations were 

 located in more northerly latitudes, were in considerably shallower 

 water, and nearer shore. This may account for the difference in 

 values. An examination of saturation of dissolved oxygen at other 

 oceanographic stations (Table 8) in open waters of McMurdo Sound 

 slightly farther north of the icehole station, reveals similar un- 

 saturated water. The 26 January 1960 station values for oxygen 

 saturation agree very closely with those obtained on 10 January 1961 

 at the icehole. Surface values for stations in the Ross Sea to the 

 north of McMurdo Sound in much deeper water also show unsaturated 

 water. Off the Ross Ice Shelf in the Little America area, the waters 

 were supersaturated at the surface (up to 133%). 



Variations in dissolved oxygen at the icehole station probably 

 were caused by seasonal changes in the phytoplankton crop and from 

 the introduction of foreign water by currents. During the latter 

 part of November, McMurdo Sound's open waters develop a bloom of 

 diatoms which makes the water taste fishy and, when concentrated in 

 a plankton haul,- smell like a newly opened can of raw oysters. This 

 was not true at Wilkes Station in East Antarctica at a latitude near 

 that of the Australian base at Mawson. As mentioned before (Tressler, 

 1960), this difference in the productivity of the two areas is be- 

 lieved to be due to the differences in the type of rock structure at 

 the two places. At Wilkes Station, granitic rocks in the main appar- 

 ently give off less nutrient material than the volcanic rocks at 

 McMurdo. This was pointed out by Lisitsyn in his report on Russian 

 oceanographic observations off East Antarctica (Lisitsyn, 1959). 

 Why such a plentiful crop of phytoplankton as that produced at McMurdo 

 should not cause supersaturation in the upper layers is a question. 

 Strong current action in the northern half of McMurdo Sound may dis- 

 sipate the amount of oxygen in the water and some may be lost to the 

 atmosphere by wave action, high waves being the common state in this 

 body of water. Also it is possible that larger micro-organisms may 

 be in sufficient abundance to use up the oxygen. Whales are numerous 

 in McMurdo Sound indicating the presence of abundant food. The 

 Euphausidae or Krill are seen in large numbers on the undersides of 

 upturned ice blocks. In the ice-covered water at the icehole station, 

 currents alone probably could cause variations in the dissolved oxygen 

 content. The rise noted in the last station (7 March 1961) came a day 

 or so before a 2-day storm. 



F. Conductivity and pH 



Although these two parameters were not measured regularly, on one 

 occasion each, determinations were made at different sampling depths. 



56 



