Schindler DW, Hecky RE, Findlay DL, Stainton MP, Parker BR, Paterson MJ, Beaty KG, Lyng M, Kasian SEM
whole ecosystem, lakes, nitrogen limitation, freshwater, cyanobacteria blooms, Experimental Lakes, Nutrient limitation, phosphorus, mesocosm, Ontario, Canada, >50m3
Lake 227, a small lake in the Precambrian Shield at the ExperimentalLakes Area (ELA), has been fertilized for 37 years with constantannual inputs of phosphorus and decreasing inputs of nitrogen totest the theory that controlling nitrogen inputs can control eutrophication.For the final 16 years (1990–2005), the lake wasfertilized with phosphorus alone. Reducing nitrogen inputs increasinglyfavored nitrogen-fixing cyanobacteria as a response bythe phytoplankton community to extreme seasonal nitrogen limitation.Nitrogen fixation was sufficient to allow biomass to continueto be produced in proportion to phosphorus, and the lakeremained highly eutrophic, despite showing indications of extremenitrogen limitation seasonally. To reduce eutrophication, the focusof management must be on decreasing inputs of phosphorus