When that cold front moved through did you have any rain? This would be an important factor. It sounds like you didn't, but sudden changes in temperature can create a turnover effect. Usually in the fall, cooling surface temperatures from cool rains, cold nights or high winds make a pond "top heavy" for lack of a better term and you have a sudden mixing of the stratified layers of a pond. This mixing brings organic matter and anoxic water from the bottom up into the water column and you can see some mortality. I'm not aware of a turnover that would occur this early, but that cold front was unbelievable! Our air temperatures in Lincoln dropped 24 degrees in 50 minutes.
