Anything on dissolved oxygen in rivers?

Dissolved O2 in rivers means the amount of O2 in terms of ml/mg per litre of water.

Lesser the temperature,lesser the salts dissloved,more the turbulence,greater is the DO2.Higher the temperature,more the salts dissolved,higher the CO2,more of decaying biota,lesser is the amount of DO2.

Fishes need at least 3mg/L of DO2 for its survival - which is always available in rivers,unless in certain localized areas where there is pollution/decomposition of organic matter.

The gas has almost no effect on algae,as very little of DO2 is required by them during night time.

Dumping of organic wastes/matter can seriously deplete DO2 especially in those places as decomposing bacteria will place a heavy demand on Oxygen. As one proceeds a little further,from the dumping ground/place, one can observe a slightly more amount of the gas.Further down,the availability of O2 will show appreciably good levels.

Suspended organic matter will bring down the level,whereas presence of algae will bring up the level,during day time.