This photo is one of the first I took with an N5100. I was surprised by the level of detail in the reflection; it was much less bright in person, at least as far as I recalled. The camera was set to store JPG, so it would have run the ADL algorithm. Is that why the reflection is so vivid?
No. Active D-Lighting would have helped retain a little more detail in the bright highlights on the tree bark everywhere in the picture, but it wouldn't have affected the bulk of the reflection, which hovers around the midtones.
The unexpected effect can probably be put down to the difference between your eye seeing changes in the reflection averaged over time as the surface of the water moves and the camera's 1/60s shutter speed. A fraction of a second earlier or later, and you probably would have seen more distortion and scattering, giving something a little more like, say, Monet's Water Lilies series. A longer shutter speed would probably have given you something considerably less sharp and distinct.
In any case, getting used to the difference between ordinary visual perception and the several different "realities" the camera can provide depending on aperture, shutter speed and overall exposure is one of the keys to successful photography. It's always a bit of an experimental crapshoot unless you're in control of everything in a studio, but knowing what will change and why will help you plan your pictures. And give you an idea when squinting, winking and blinking to look for those changes might be a good idea.