what are the situations wherein oxygen depletion occurs?

Answer 1

Well fire depletes oxygen, so if you have a closed space w/ a fire, the fire will deplete all the oxygen.

Also, if you have an enclosed space w/ organisms that use oxygen, they could use it all up until the all die.

Answer 2

Typically in a lake during the summer if there are too many nutrients in the water. Temperate lakes are stratified in the summer, meaning the top waters don't mix with the bottom waters because the temperatures are different. This starts in the spring and lasts until late fall. This means that the bottom water is isolated from the atmosphere during the entire summer and cannot get any new oxygen. It only has what was dissolved in the water in the spring. Normally this is not a problem. But if there are too many nutrients (usually phosphates) bacterial growth can be high and the bacteria consume the oxygen until there is none left. Since the bottom does not receive enough light for plants and algae to grwo and photosynthesize the oxygen stays depleted until the layers mix in late fall.

The problem is that the organisms that typically live on the bottom - insect larvae, worms, and cold water fish like lake trout, need the oxygen and cannot survive the period of deoxygenation.

Answer 3

The above answer was found in wikipedia. You can find some excellent articles in there to help answer your question. All see the multitude of sources I uncovered by typing "oxygen depletion" in my search boxes:

http://search.yahoo.com/search?p=+oxygen+depletion&prssweb=Search&ei=UTF-8&fr=ytff1-&x=wrt
http://www.google.com/search?hl=en&q=oxygen+depletion&btnG=Google+Search