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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.
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).
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