Over the long term, this build-up will make algae blooms more frequent and severe, unless some method for removing phosphorus and nitrogen is found. The bottom muds in Lake Winnebago and Little Lake Butte des Morts are already very fertile from a century of phosphorus and nitrogen accumulation dating back to the erosion caused by cutting down the great Pine and Hardwood Forests of Northeast Wisconsin, and the following agricultural and urban uses. Even if no new land run-off or discharges occurred, the existing sediments would fertilize algae. Storms, boat traffic, and bottom-feeding fish like carp all stir up the sediments and make nutrients more easily available for algae growth. The system will likely stay at least somewhat fertile because of this.
Some fertility is good, because it feeds Lake Winnebago's outstanding fisheries and wildlife.
More people are building homes and businesses along the waterfront. This eliminates all the shoreline plants which used to filter phosphorus and nitrogen pollution out of the water. In addition, too many shoreline property owners install heavily fertilized and chemically treated grass lawns right up to the water's edge. Non-point pollution is one of the most serious environmental problems facing Wisconsin, partly because control programs are under funded and unmandated. Watersheds like Lake Winnebago's and Green Bay's need much more attention.