Oxygen Stratification - Lake Ecosystem
In most lakes, oxygen stratification nearly parallels that of temperature during the summer season. The amount of oxygen is greatest on the surface, gradually decreasing with depth. The surface layer has the maximum oxygen content due to two main reasons. First, being well lighted, maximum photosynthetic oxygen is produced here.
Secondly, being in intimate contact with the atmosphere, it permits free diffusion of oxygen into it from the air. The oxygen content beneath the surface water decreases as both these oxygen sources disappear. At the bottom the oxygen content decreases further due to utilisation of oxygen by decomposers occurring here.