In reading this information it is important to remember that these methods would only treat the symptoms of the lake’s problems and the treatments are only short term in duration.  As long as the excessive nutrient load is feeding the basin these methods would have to be repeated and still not solve the problem.  The only known real solution is to reduce the nutrient load entering the streams of the basin.

Another important fact to keep in mind is what we do here affects everywhere downstream of us.  The dead zone in the Gulf of Mexico at the mouth of the Mississippi is the example that directly pertains to us.  The Red Cedar Basin contributes to that problem.  This dead zone is more than 8,500 square miles in size (about the size of New Jersey).  The Department of Agriculture is addressing this problem and has created the Mississippi River Basin Initiative (budgeting $320M over the next 4 years) to work on reducing nutrient loads.  The Focus Areas in Wisconsin are the Sugar, Upper Rock, and Pecatonica River Basins.  Information on this program can be found at Mississippi River Basin Initiative.

DNR Lake Management staff has prepared these initial responses to our inquiries about alternatives to lessen the accumulation of algae in portions of lakes.  When contemplating efforts to lessen the algae densities in individual bays or channels it is important to recognize that while potentially addressing public health and welfare concerns, the effort does not improve the overall water quality of the lake.  For that to happen, reductions in the sources of phosphorus are needed.

1.  Permanently draining the lake (eliminate the dam) - Likely eliminates the algae problem but also eliminates most of the public use associated with a lake.  Worth considering for small flowages that rapidly fill up with sediments anyway but usually not supported by the public for large lakes with established public usage.

2.  Vertical Mixing Devices (such as Solar Bees) - Installation of sufficient devices to adequately mix the water column in large scale applications would be very expensive and could create navigational hazards.  In addition, the ability of such mixing to improve water quality in the absence of reductions in nutrient inputs has not been scientifically documented.  DNR has indicated a willingness to consider funding the science associated with researching this technology if another funding source was used for equipment purchase, installation and operation.

3.  Aeration - Aeration is used as a lake management technique to provide mixing in lakes during the summer stratification period to prevent anoxic release of phosphorus and during winter to prevent winterkill in shallow lakes.  Summer stratification has not been documented as contributing to the algae problems at Tainter or Menomin.  Winter aeration could be considered if serious fish kills become a regular occurrence in particularly sensitive areas.  This would not affect the summer algae situation.

4.  Lateral mixers to break up scum layers – Long term operation of outboard motors at a fixed location has been documented to release serious levels of petroleum and other deleterious substances into the water and would not be approved.  Electric mixers have been used in association with a pump in one place in WI to laterally disperse surface accumulations.  The goal was to make an area of historic high accumulations look more like the rest of the lake.  Care is needed to accurately project operating cost and logistics.  Consideration should be given to the possibility of moving the problem down the shore.

5.  Dredging - Dredging is used most often to improve navigation in areas where excessive sedimentation has occurred.  Dredging may help improve flow through Wolske Bay but costs may be prohibitive.  Dredging as an algae control mechanism would only work where the sediment was considered a major source of phosphorus for the lake.  Information collected to date indicates that sediments are not a significant source of phosphorus to Tainter and Menomin Lakes.

6.  Chemical treatment (alum - aluminum sulfate, lime - calcium carbonate, copper sulfate, others)  

Alum is used to control the release of phosphorus from the sediments of lakes that undergo periods of anoxia during the summer months, releasing a large amount of phosphorus into the water column and stimulating summer algae blooms.  Information collected to date indicates that sediments are not a significant source of phosphorus to Tainter and Menomin Lakes.  The use of alum to treat phosphorus flowing into the lake is feasible for flowing waters with high phosphorus concentrations and relatively low flow.  To date this has been used primarily in wastewater treatment plants and stormwater collection systems.  Treatment of rivers the size of the Red Cedar and Hay Rivers would be extremely expensive.  Other problems include turning the rivers white near the point of alum application and accumulation of settled alum in the river channel and lake.

Lime, or calcium carbonate, is similarly unsuited for large scale applications and can have unintended effects on aquatic plants, fish and aquatic life due to the volume of material needed to bind up available phosphorus.

Copper sulfate can control algae but is toxic to non-target aquatic organisms at dosages necessary to control algae and will accumulate in the sediment.  Moreover, treating blue-green algae directly with herbicides releases toxins into the water and could worsen the risk to human health.

7.  Barley Straw - Barley straw has some reported effectiveness in small ponds.  The effectiveness of large scale applications has not been proven.

8.  Surface skimming/vacuuming.  To our knowledge, this has only been used as a means of to supplying the market for algal dietary supplements, which cannot make use of the toxic forms of blue green algae causing a problem in Wisconsin.  Moreover, this technique has not been employed as a large-scale lake management technique.  A proposal to use booms to direct windblown algae scums to a collection point is being considered in the Madison Lakes to protect beaches and other public use shorelines.  A mechanism for collecting and removing the scum has not yet been identified.  Wastewater treatment technology has recently advanced in the use of microfiltration and centrifugation. While these technologies might be applicable to separating algae from water in a skimming / vacuuming operation, the associated costs would likely be high and the logistics of disposing of the separated solids would need to be addressed.

9.  Harvesting for Biofuel - See # 8 for issues associated with harvesting. To our knowledge, research on algae as biofuels has been limited to tightly controlled conditions as opposed to fluctuating natural populations of mixed algal species.

10.  Converting bays to wetlands – Similar to #1, this option permanently removes public uses (boating, fishing etc) from public waterways and may eliminate important spring fish spawning habitat.  It could move the algae problem to a different location with no impact on the overall algae conditions in the lake or the level of odor.  Many created wetlands turn out disappointing because they do not yield the assortment of functional values associated with natural wetlands and get overtaken by invasive species.  Likely would be expensive and could take special legislation.