Carter Lake is a 315 acre oxbow lake along the Missouri River between Nebraska and Iowa. Elevated phosphorus levels resulted in cyanobacteria (a.k.a.blue-green algae) blooms and subsequent microcystin algae toxin production. From 2005-2008, beach warnings were posted for 21 of the 80 weeks of peak summer recreation. A whole lake alum treatment was completed in May 2010, a success story jointly published by Nebraska and Iowa officials can be downloaded below.
The alum treatment resulted in the following changes:
- Total phosphorus declines of 72%
- Total nitrogen declines of 52%
- Algae toxins are virtually non detectable and beaches have not been closed since the treatment
- Water clarity has improved
- Newly stocked game fish have flourished
- The lake is proposed to be removed from USEPA’s Clean Water Act section 303(d) list for impaired waters due to algae toxin