I analyzed lake fertilization (with nitrogen and phosphorus) of Idaho's Sawtooth Valley Lakes. These lakes had deep chlorophyll maxima (DCM) existing at low light levels and accounting for 36-72% of the lakes' primary production. Epilimnetic fertilization of Redfish Lake mesocosms increased primary productivity and chlorophyll a, but decreased Secchi depths and light available in the meta- and hypolimnion. A simulation model showed that increased epilimnetic primary productivity from fertilization was large, outweighing the slight production decrease in deeper strata caused by self-shading.

Metalimnetic fertilization of Pettit Lake mesocosms was equal to or more effective than epilimnetic fertilization in increasing chlorophyll a, phytoplankton biovolume, and primary productivity, yet caused smaller changes in periphyton growth and water clarity.

Modeling and empirical evidence indicated, both presently and before dams existed in the migration corridor, that marine-derived nutrients were not of major importance to lake production, contributing only $\sim$3% of Redfish Lake's phosphorus load.