Should partially full layers return tsr output?

I am trying to output tsr files for all the layers of certain segment so I can calculate a depth average. I am surprised to find that the top layer (layer 2) returns 0.0 for all water quality concentrations when the reported depth would predict that layer 2 should be partially full. I’ve been specifying layer about in the TSR ELEV card (i.e. “-2” for layer 2). Is this an expected result? Thanks, Dan Turner