[whittaker] bottom DEPOSITS OF McKAY LAKE 153 



in the character of the plant life and consequently in the nature and 

 rate of deposition of the bottom deposits. Had a similar change in 

 sediment occurred in Fairy Lake the climatic factor would be strongly 

 upheld, but as noted above conditions in the two lakes are different. 



In spite of the meagre information obtained it would appear that 

 the chocolate red beds deposits are seasonal and that the pair of one 

 chocolate brown and one grey layer represent a year. The grey 

 layer represents the spring sedimentation when the waters which 

 ordinarily slip into the lake come down by many miniature torrents 

 bringing down considerable material from the marl beds above. A 

 bed of organic material has been formed in the summer and fall from 

 algae growth on the bottom as well as organic dust detritus such as 

 pine pollen and decomposed leaves. It must be remembered that 

 man has changed the character of the shoreline and in such a small 

 lake has been able to affect its sediments. In utilizing the under- 

 lying sands the marl has been removed so that now it occupies only 

 a fraction of its former area, so that now the lime content of the spring 

 deposit is almost negligible. By clearing away a large part of the 

 coniferous forest the organic content of the sediment has also been 

 lessened. Anyone who has seen the pollen covering upon one of our 

 northern Ontario lakes in June or July can realize what an important 

 contribution is made by it to bottom deposits. 



Influence of Bathymetric Range and Bottom Environment 

 Upon the Molluscan Fauna 



While the influence of the bottom and depth upon tha molluscan 

 fauna was not one of the primary objects of this investigation attention 

 was given to it in a quantitative way when possible. The best work 

 done of this nature on freshwater lake faunas is that of Dr. F. C. 

 Baker on Oneida Lake.^ In a very general way it may be said that 

 there is a certain zone of maximum productivity in shallow water a 

 short distance from shore, while in the deepest parts of the lake no 

 living molluscs were obtained at all. In general it may be said that 

 the fauna and flora occupied the same area. In McKay Lake no 

 plants live in water over ten to twelve feet deep, and no animals were 

 found beyond that limit except some insect larvae. The bottom as 

 noted previously may be divided into: 



W. C. Baker. The Productivity of Invertebrate Fish Food on the Bottom 

 of Oneida Lake, with special reference to Molluscs. Technical Publication No. 9 of 

 the New York State College of Forestry at Syracuse University, 1918. 



