Lake Erie Nutrients
In Lake Erie, excessive growth of cyanobacteria, or blue-green algae, poses significant threats to the ecosystem and human health. Algae can grow rapidly, usually triggered by an excess of phosphorus and nitrogen. This rapid overgrowth is called an algal bloom, which can be harmful if ingested or touched. Sometimes dense blooms of algae form mats or scums at the lake surface. When the algae die and sink to the bottom of the lake, oxygen is consumed as the algae decompose. To prevent harmful and nuisance algal blooms and formation of low oxygen “dead zones” in the lake, the U.S. and Canada are working in partnership with states in the Lake Erie watershed and the province of Ontario to reduce the amount of phosphorus entering Lake Erie.
![Map of Lake Erie and surrounding creeks, rivers, basins](/system/files/styles/large/private/images/2023-10/lake-erie-map.png?itok=F9OVZL84)
About Annex 4
The Great Lakes Water Quality Agreement Nutrients Annex (Annex 4) is a commitment between the U.S. and Canada to manage nutrients in the Great Lakes.
![Wetland aerial image in Region 5](/system/files/styles/large/private/images/2023-10/dap-image-wetland.jpg?itok=f7zD6snl)
Domestic Action Plans
Domestic Action Plans are the “road map” for phosphorus control efforts undertaken by states, provinces, and both federal governments.
![White rising bar chart on blue background with copy space. Business economic and money investment concept. Goal and success theme. 3D illustration rendering graphic design.](/system/files/styles/large/private/images/2024-03/chart.jpg?itok=MVUF6Oiu)
Status and Progress
The U.S. and Canada are tracking progress under the Domestic Action Plans to achieve water quality goals.
Visit EPA’s website for more information on Harmful Algal Blooms in Water Bodies | US EPA