CHAPTER 9 

 AQUATIC CLIAIAX COMMUNITIES 



FRESH WATER COMMUNITIES 



Introduction. Only those aquatic communities that are similar in 

 general character to the climaxes on land are considered as water 

 climaxes. These are the stable and relatively permanent communi- 

 ties that show some degree of biotic development; their constituents 

 exercise a large control over the habitat and over community com- 

 position. 



There are two or three types of climaxes in water, namely, fresh- 

 water climaxes that characterize very large fresh-water lakes and slug- 

 gish streams, and marine communities which are probably climax and 

 characterize the ocean. In addition, there are alkaline and very salty 

 lakes in arid areas of internal drainage, which contain life and in 

 which climaxes probably occur. Generally speaking, the communities 

 included in this discussion are on silt (terrigenous) , as opposed to 

 humus, bottoms. The rai)id accumulation of humus in small fresh- 

 water lakes and ponds assigns all small bodies of still fresh water to 

 the seres of terrestrial climaxes; some shore waters of the sea are 

 similar in character. 



HYDROCLIMATES 



The major communities on land are dependent on a complex of 

 physical factors called climate. It is not unusual to refer to the com- 

 binations of various physical and chemical conditions in the sea and 

 fresh water as hydroclimates (Wasmund, 1934), and such a procedure 

 is not difficult to justify, since it concerns physical conditions and is 

 not without earlier precedent (Huntsman, 1920). Animals live in 

 water at all depths, both on the bottom and suspended in the medium. 

 This distribution stands in contrast to terrestrial climates, in which 

 only the lower atmosphere is in contact with most organisms. Be- 

 cause of physical properties and by virtue of the contained inhabitants, 

 water and water climates exhibit some of the properties of soil and soil 

 conditions. Accordingly, any attempt to analyze marine and fresh- 



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