Algal productivity in 49 lake waters as determined by algal assays

Algal assays were conducted on waters from 49 American lakes to determine whether phosphorus, nitrogen, or some other nutrient was the limiting factor upon algal productivity.A comparison of the known trophic state of 23 American lakes and their bioassay response is presented. Phosphorus limited algal growth in 35 of the 49 lakes assayed. Nitrogen was limiting in eight lakes and constituents other than nitrogen and phosphorus were limiting in six lakes. The results of this study indicated phosphorus limitation decreased as the productivity of the lake waters increased.