The nitrogen and phosphorus dependence of algal biomass in lakes: An empirical and theoretical analysis1

An analysis of mean growing season concentrations of chlorophyll, total phosphorus (TP), and total nitrogen (TN) in 228 north latitude lakes confirms previous observations that chlorophyll yield is dependent both on the phosphorus concentration and on the TN:TP ratio. Of two modified chlorophyll models which depend explicitly on both nitrogen and phosphorus developed and tested, one, a multiple regression model, appears to greatly reduce the error of chlorophyll prediction in lakes. A theoretical framework is presented which provides an explanation for the observed effects of N:P ratios.