49-50 degrees but my probe doesn't go deep enough to check temps say at 20-24". I also wonder if you are on to something that the temps measured right at the top of the oak leaves with sunlight might be quite a bit warmer than the pond bottom right next to it...and only an inch or so deeper.
Also my pond bottom texture and sand composition is much different this year than last. I have enough soilfloc in my sediment now that when you touch the pond bottom with a stick it clunks like concrete. You can't even push a stick into the bottom, you have to pound or drill it in. I used to get a plume of silt when I scratched the bottom sand but now no plume. I don't know if that polymer concrete material heats up or not but it seems that the beds of oak/maple leaves are very popular. All of the ribbons are laying in 8-10" of water on leaf beds, none on dirt, so far none in the reeds nearby (sedge) none in the sticks
