would be able to make on productivity of this lake from a considera- 

 tion of other limnological features. The pH is low (6.0-6.4). The free 

 carbon dioxide is 1.25 ppm near the surface, although at the bottom 

 it is high, 10.5 ppm. The conductivity is low, the mineral content al- 

 most non-existent. It is reported that the water from Crystal Lake 

 can be used safely in storage batteries. Repeated tow samples from 

 this lake ( July- August ) yielded scarcely a single plankter, and there 

 was a negligible amount of attached filamentous algae in the shallow 

 water zone. On the bottom, at 10-15 meters, however, there is a car- 

 pet of the aquatic moss Drepanocladtis fiuitans and a meager algal 

 flora of 15 species (including desmids). The stratum of vegetation 

 accounts for the rise in chlorophyll content, shown by Kozminski 

 (I.e.), in a layer where there is also an increase in the amount of 

 available carbon dioxide. 



PHYSICAL-CHEMICAL FACTORS 



The quantity and quality of the algal flora is affected by many 

 edaphic factors, and in turn these plants produce effects in the phys- 

 ical-chemical factors in the medium. These effects may directly or in- 

 directly influence the biota of the environment, sometimes very dras- 

 tically. Algae alter the oxygen and carbon dioxide content of the 

 water, cause the pH to fluctuate, contribute to the nature of bottom 

 sediments, and in other ways initiate series of cause-effect inter- 

 actions. It is recognized that these changes are involved in what may 

 be called algal ecology. This is an iU-defined term and broad in its 

 application because it must cover such a complex of interacting fac- 

 tors and processes of nature. Since life itself is the product of these 

 processes and the responses that protoplasm makes to them, it is not 

 possible to regard any one ecological factor as more important than 

 another. Carbon dioxide and oxygen might be selected arbitrarily for 

 primary consideration. 



Carbon Dioxide 



Carbon dioxide and carbon dioxide tension ( Burr, 1941 ) are criti- 

 cally important and only those bodies of water abundantly supplied 

 with this gas, free or at least available, can support a luxuriant 

 growth of algae. The quantity of carbon dioxide is regulated by 

 a number of factors, many of which, in turn, are related to climatic 

 conditions and geological events of the remote past. The temperature 

 of the water at different times of the year and in different strata, the 

 amount of carbon dioxide released by respiration, the chemical 

 nature of the bottom and the overturn of organic matter by bacteria, 



[38] 



