You are correct, there is a specific example. I won't offer up the name for online safety reasons. I'm not affiliated with any organization and this is a passion project.

The lake in question, like the one mentioned in Florida, is mostly spring fed. The rock type is much more dense. It is classified as oligotrophic despite its boundaries having been deforested, used for agriculture for over a century, and summer home development. I find that bizarre and am attempting to gain a broader scope of understanding of the systems before possibly spending next winter counting diatoms from core samples.

Furthermore, I suspect the vast majority of bathymetric map data was collected via measuring a rope with a weight at it's end. Such a methodology would overlook the characteristic I've been referring to.

Lastly, I hypothesize lake bottoms which share this characteristic maintain other anomalies to limnology models.