|MadSci Network: General Biology|
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.
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