Temperature has a major role in pond stratification. Temperature differences causes density differences. Density differences results in two layers being formed within a pond. Oxygen Dissolved oxygen refers to oxygen gas that is dissolved in water. Fish need oxygen just like land animals do.
Fish absorb oxygen directly into their bloodstream using their gills.
Fish cannot live without oxygen. Oxygen depletion is the cause of many fish kills. Low oxygen stress is the cause of disease outbreaks. The amount of oxygen in water decreases as temperature and altitude increases. As temperatures increase, fish metabolism will increase so they consume more oxygen.