Assessing and addressing the re-eutrophication of Lake Erie: Central basin hypoxia

article Relieving phosphorus loading is a key management tool for controlling Lake Erie eutrophication. During the 1960s and 1970s, increased phosphorus inputs degraded water quality and reduced central basin hypolimnetic oxygen levels which, in turn, eliminated thermal habitat vital to cold-water organisms and contributed to the extirpation of important benthicmacroinvertebrate prey species for fishes. In responseto load reductions initiat- ed in 1972, Lake Erie responded quickly with reduced water-column phosphorus concentrations, phytoplankton biomass,and bottom-waterhypoxia(dissolved oxygenb2 mg/l). Since the mid-1990s,cyanobacteriabloomsin- creasedandextensivehypoxiaandbenthicalgaereturned.We synthesizerecentresearchleading toguidancefor addressing this re-eutrophication, with particular emphasis on central basin hypoxia. We document recent trends in key eutrophication-related properties, assess their likely ecological impacts, and develop load response curves to guide revised hypoxia-based loading targets called for in the 2012 Great Lakes Water Quality Agreement. Reducing central basin hypoxic area to levels observed in the early 1990s (ca. 2000 km 2