DO levels also fluctuate seasonally and over a 24 hour period. The amount of DO also varies with water temperature and altitude. In general, various sources of competition for dissolved oxygen mean that some animals will not be able to survive in the aquatic system due to low dissolved oxygen. Smith, Robert Leo. As stated above, DO is one measure that fluctuates with temperature.
Most aquatic organisms depend upon certain temperatures in order to sustain their life functions.
Temperature also effects the process of photosynthesis and the sensitivity of certain organisms to toxic waste, parasites, and diseases. The degree of acidity or alkalinity, or pH, of water reflects the carbon dioxide content as well as the presence of organic acids and pollution. At higher levels, water is more alkaline and at lower levels, water is more acidic. The higher the pH of stream water, the richer natural waters generally are in carbonates, bicarbonates and associated salts. Such streams support more abundant aquatic life and larger fish populations than streams with acid waters, generally low in nutrients.