With light penetration of 32" and a pretty dense phytoplankton community (bloom) I think noticeable DO fluctuation would occur depending on amount of sunlight the surface receives. Remember the water column circulation you have will move the surface DO production due to phytoplankton photosynthesis throughout the water column. This will keep the surface DO lower compared to non-aerated pond. At least this is my explanation. Also in July the water was warmer at 65-70F compared to Sept of 49-54F and maybe the phytoplankton produced more oxygen in warmer water? Temperature and lack of sunlight may have acted together? Only a guess.

Last edited by Bill Cody; 10/08/18 07:35 PM.

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