Pond Boss Forums INTRO Questions & Observations Is there a right answer? - Pond Depth

Rrobin - Yes you are correct. unaerated deep water below the thermocline can have low or no DO, but not always. Depth of DO production or availability is dependent on how clear the water is thus allowing sunlight to penetrate so vegetation and phytoplankton can produce oxygen due to photosynthesis. Clear water with visibility of 7ft will allow oxygen production as deep as 14 to 18ft regardless of a thermocline. It is called the euphotic or photic zone; learn about it and how to measure it.

https://www.lakeaccess.org/ecology/lakeecologyprim9.html