Phos found to be the algae buildup culprit

Edmonton, Alberta — Water managers are on the wrong track concentrating on reducing nitrogen buildup in lakes to control eutrophication and the growth of algae, according to a University of Alberta biologist, who has found that the only method that has had proven success is reducing input of phosphorus. “Erroneous assumptions about ecosystem processes and lack of accounting for hysteresis during lake recovery have further confused management of eutrophication,” said David Schindler. “I conclude that long-term, whole-ecosystem experiments and case histories of lake recovery provide the only reliable evidence for policies to reduce eutrophication. The only method that has had proven success in reducing the eutrophication of lakes is reducing input of phosphorus.” And, Schindler insisted, it can be done at a fraction of the cost of controlling nitrogen. “There are no case histories or long-term ecosystem-scale experiments to support recent claims that to reduce eutrophication of lakes nitrogen must be controlled instead of or in addition to phosphorus. Before expensive policies to reduce nitrogen input are implemented, they require ecosystem-scale verification. The recent claim that the ‘phosphorus paradigm’ for recovering lakes from eutrophication has been eroded and has no basis. Instead, the case for phosphorus control has been strengthened by numerous case histories and large-scale experiments spanning several decades.” Schindler said nuisance blooms in Lake Winnipeg have nearly doubled since the mid-1990s as the result of a recent rapid increase in loading and concentration of phosphorus from rapidly increased livestock production and the use of synthetic fertilizer, along with smaller contributions from the city of Winnipeg and other development and spring floods greatly enhancing the phosphorus transfer contributions. He stressed that recovery of the lake will require reducing both agricultural and major urban sources of phosphorus and, if possible, the frequency and intensity of flooding in the Red River watershed. Flooding will be increasingly difficult to control if modeled predictions for increased precipitation under climate warming materialize. Even with targeted reductions in phosphorus inputs of 50 percent and measures to control flooding, recovery of the lake is expected to be slow because of phosphorus recycled from sediments and the climatic sensitivity of this shallow lake and the flooding of the Red River.