and currents, there is abundant opportunity to replenish the supply of 

 oxygen. Algae are commonly abundant at this time of year, and in the 

 presence of sunlight they aid materially in maintaining a high oxygen 

 content. During the winter months, low temperature retards the 

 process of deconposition, and there is less demand on the supply of 

 oxygen. However, the water is covered with a layer of ice which pre- 

 vents interchange of gases with the air. The ice is frequently covered 

 with a blanket of snow preventing free entrance of sunlight, and the 

 amount of both sunlight and phytoplankton are usually reduced in winter. 

 Hence photosynthesis is not as important a factor in maintaining the 

 supply of oxygen as in summer. It appeared possible, then, that the 

 water of Western Lake Erie might become very low in oxygen during the 

 winter. Accordingly, sa;r.ples were taken at four stations near the west 

 shore of the lake in February, 1930. A list of the stations, with 

 their location and other pertinent data are given below; 



Station A. Located 2 miles southeast of the shore at Stony Creek, and 

 roughly 1 mile from Stony Point. Depth, 6.1 meters. Samples taken at 

 surface and bottom on February $, Ice 8,5 inches thick, with little 

 snow on the ice. Sky cloudy. Water clear. 



Station B. Located 1 mile east of Monroe Light at the mouth of River 

 Raisin. This station is near Station 213 as shown in Table 36 Depth, 

 5.3 meters. Samples taken at surface and bottom on February 7. Ice 

 8 inches thick, with snow distributed in patches, covering perhaps 

 one half the surface. Sky cloudy. Water clear. 



Station C. Located in La Plaisance Bay, 2.5 miles southeast of pier 

 at Bolles Harbor. Depth, h»7 meters. Samples taken at surface and 

 bottom on February 5. The bottom sample for oxygen was lost later by 

 freezing. Ice 10 inches thick. Snowing heavily. Water clear. 



Station D. Located 3 miles roughly ESE of the shore at Lakeside, 

 Michigan. This station is about 3.75 miles from Toledo Harbor Light, 

 Depth, 5 meters. Samples taken at surface and bottom on February 7. 

 Ice lli inches thick. Snow distributed in patches. Sky cloudy. Water 

 turbid. 



The chemical data are shown in Table I18, 



Chemical conditions at the different stations were remarkably 

 uniform. The oxygen content was unexpectly high; it ranged from 10. Ij to 

 12.1 parts per million, and from 73 to 83 per cent of saturation. The 

 actual amount of oxygen present was thus greater than in any of the 

 summer samples taken in this region, and the lowest per cent of satur- 

 ation was not greatly lower than in many of the summer samples. There 

 was an excess of free carbon dioxide in every sample, but the excess 

 was small, and pH did not fall below 7,5, 



135 



