Predicted effects of fertilizers upon the algae production in Fern Lake

1. With the object of predicting effects of different amounts of fertilizers, upon the rate of primary production in Fern Lake, a bioassay was carried out in a series of 14 twenty liters glass carboys. 2. The experiment revealed that the rate of gross production increased nearly proportionally with the amounts of fertilizers added and a maximum increase of 180 times the orginal rate of gross production was obtained. 3. When iron was included with the fertilizers colloidal substances were forined acting upon the transparency of the water. When it was excluded it became limiting on the rates of primary production. 4. It is demonstrated that due to reduced transparency the inclusion of 100 ppm iron would not increase the total primary rate of production of the lake any further. 5. Suggestions for the fertilization of Fern Lake are given