The present investigation is carried out using lake water from Bhiwandi city. Most of the biological organisms, micro-organisms present in the water require oxygen for their survival and growth. They utilize the oxygen present in the water. The biological processes decompose oxygen present in the water which may result in decrease in the level of oxygen to such extent which is necessary for normal growth of other aqua fauna. It is found that decline in dissolved oxygen concentration is one of the most important factor that directly affect the lifecycle of most of the aquatic animals. The results of oxygen utilized by the biological process which may not necessary for aquatic ecosystem, are then compared with the standard values prescribed by the standard bodies.