March 6, 2014 — Reducing the size of the Lake Erie "dead zone" to acceptable levels will require cutting nutrient pollution nearly in half in coming decades, at a time when climate change is expected to make such reductions more difficult.
That's one of the main conclusions of a comprehensive new study that documents recent trends in Lake Erie's health. It offers science-based guidance to policymakers seeking to reduce the size of toxic algae blooms and oxygen-starved regions called hypoxic zones, or dead zones-two related water-quality problems that have seen a resurgence in the lake since the mid-1990s.
The report from the multi-institution EcoFore-Lake Erie project states that a 46 percent reduction in the amount, or load, of phosphorus pollution would be needed to shrink Lake Erie's Central Basin hypoxic zone to a size last seen in the mid-1990s-a time that coincided with the recovery of several recreational and commercial fisheries in the lake's west and central basins.
Phosphorus is a nutrient used in crop fertilizers. Excess phosphorus washes off croplands during rainstorms and flows downstream in rivers that feed the Great Lakes. Once in the lakes, phosphorus can trigger algae blooms. When the algae die and sink to the lake bottom, oxygen-consuming bacteria feed on them and create hypoxic zones in the process. Many fish shun these oxygen-starved waters, which significantly reduce the amount of suitable habitat available to the fish.