How can Eutrophication be slowed?

Eutrophication is the process in which lakes receive nutrients (phosphorus and nitrogen) and sediment from the surrounding watershed and become more fertile and shallow.  Eutrophication can be slowed by reducing nutrient and sediment addition to the lake.  It is nearly impossible to turn a eutrophic lake back into an oligotrophic lake, but it is possible to turn back eutrophication somewhat.CulturalEutrophication

Reducing Nutrient Addition

Since phosphorus is the main cause of eutrophication in most Minnesota lakes, reducing phosphorus addition to the lake is the most effective way to slow eutrophication.  Phosphorus can enter a lake through poorly managed or failing septic systems, phosphorus detergents, phosphorus lawn fertilizers, agriculture, and animal feedlots.  To locate the source of eutrophication for a specific lake, complete a ground truthing study and a lakeshore inventory.  A ground truthing study involves inspecting the inlets to the lake and identifying any sources of phosphorus along them that is adding nutrients to the stream and then eventually the lake.  A lakeshore inventory involves driving a boat slowly around the whole shore of the lake, taking a photo of each parcel and evaluating land management practices.  The parcels on the lake can be summarized by percentages; for example, 60% of the parcels have proper shoreline vegetation buffers and 40% do not.  Educating lakeshore property owners on how to limit phosphorus addition to the lake is paramount.

Reducing Sediment Addition

When erosion occurs along a lakeshore or a stream bank of a lake inlet, that extra soil can get washed into the lake.  The extra soil particles cause cloudier water and eventually settle on the bottom of the lake making it mucky and less stable.  The soil also carries with it nutrients such as phosphorus and nitrogen which can cause algal blooms.  During a groundtruthing study and lakeshore inventory, note the areas where erosion is occurring and take steps to stabilize the area.  The most effective stabilization technique is a shoreline buffer of native plants; however, on very steep shores where plants wouldn’t establish riprap can be effective (more information on shorline buffers and restoration).