Bioassay of Water from a Concretion-Forming Marl Lake

Using a pure, bacteria-free culture of Nostoc muscorum as a bioassay test organism, it was found that the water of Bass Lake, Livingston Co., Michigan, had a severe phosphate deficiency and less severe deficiencies of K, Fe, Mn, and Mg. Emission spectrographic analyses showed that the concretions had Ca as the principal constituent, Mg as the major impurity, and Fe, Si, Mn, Al, and Sr as minor impurities. When boiled, the lake water formed a white precipitate of CaC03, which could be prevented by the addition of a very small amount of KtHPOd. It is suggested that concretion formation in marl lakes is associated with extreme phosphate deficiency.