A vital key to the management of lake and reservoir eutrophication has been the development of models linking water body nutrient concentrations to aspects of water quality that are considered by the public to be important and worth preserving. Perhaps the most commonly identified Quality Variable of Con- cern in aquatic ecosystems is the accumulation of nuisance levels of algal biomass, which are easily observed by the public. Moreover, the reduction of algal biomass to levels that are acceptable to the public has been a feature common to all successful eutrophication control efforts. As would be expected from Liebig's Law of the Minimum.