(WPF)

Water depth may divide the water column biologically. My general impression is that different species are found at different depths. These are at the deepest level. I am not skillfully enough to make accurate pronouncements, but that is my general impression. The largest group of organisms are close to the water surface--the deeper into the water column, the smaller the number. Water clarity is highest at middle depths (just below the biofilm level).

https://youtu.be/yz0d8nscN9A