Re: What organisms live in specific types of water?

     The pH of most inhabited water must approach neutral status for the 
body fluids of living cells to remain in that same state. So sea water in 
particular always provides a sort of mothering environment for life. Almost 
every form of life will therefore inhabit the ocean with a major exception of 
insects or flowering plants. These organisms never use sea water alone for a 
whole life-cycle. Unfortunately, you omit river water from your studies. Rivers 
are particularly important for humans but also many other Vertebrates, 
Arthropods and Plants which are able to adapt to slightly different pHs. Lakes 
often contain organisms which have evolved from river species because they 
colonised the habitat from a running water situation.
     Tap water, drinking water and pool water are all designed to kill certain 
organisms using chlorine, sulphur dioxide or other agents that cause the 
chemical nature of the water to prohibit life. I don't know whether your 
question is devoted to the few organisms which have adapted to these 
extreme conditions or you have interests in the communities of fresh and 
marine waters. To answer the former you will be able to discover much 
more advanced work on the subject among microbiological texts because 
bacteria and their lesser co-habitants, the viruses are almost the only living 
things that are able to mutate fast enough to colonise these quite new 
environments. One example only is the preference of Legionnaires Disease 
for air-conditioning units and the minute water droplets which they distribute. 
I hope this brief discussion gives you some simple or adequate ideas. The 
alternative for me would be to me immensely boring about every known 
beast to live in or on the fluid of life.