Lake Management Techniques: Algaecides
By David Ernes – Lake Management Committee
In an upcoming series of articles, the Lake Management Committee will be presenting a brief overview of the mitigation options we are investigating for our lake. The purpose of these options is to reduce the frequency and intensity of harmful algal blooms (HAB). The techniques can be summarized as being mechanical, biological or chemical in nature.
Algaecides are one example of a chemical option. While they kill the algae population, they are not retained in the water column. Instead they either sink to the bottom and become mixed with the sediment or breakdown to a form that is no longer effective. As such they must be applied at a frequency that is determined based on the characteristics of each lake (e.g. nutrient sources). It is important to realize that the effectiveness and longevity observed for one lake is unlikely to be predictive for another lake, like ours.
The two most common types of Algaecides used for HAB’s are based on either copper sulfate or hydrogen peroxide. The former has been used for years and is highly effective at killing cyanobacteria. While most people have heard that copper can be toxic to fish, plants and other species, this side effect largely depends on the form of copper used and its dosage. There has been a lot of discussion lately related to the use of a new copper-based product, LakeGuard Blue, which was used successfully at Chippewa Lake. They reported no adverse effects. Since the product allows the copper to stay suspended in the water column for up to 24 hours, a lower dose can be effective.
The RRA Board, as well as members of the LMC and EAC, recently attended a Zoom call with representatives from Chippewa Lake. We also hosted a representative from BlueGreen Water Technologies, the manufacturers of the product, at our lake. Both spoke highly of the product, and its efficacy. However, there is no guarantee that we would see the same success or longevity. The supplier also advocates testing to be used in conjunction with the product for the best outcome.
The second product, often referred as SPC, or PAK 27, breaks down in contact with water forming hydrogen peroxide. The released peroxide destroys cyanobacteria and has the added effect of also breaking down the toxins that can be released when they die. SPC does not accumulate, rather it further breaks down to water and oxygen. The disadvantages are a higher cost, and the fact that it is not as effective as copper on HAB. BlueGreen has a product, LakeGuard OXY, with the same suspension properties as the Blue product and is currently being evaluated in Florida.
Overall, these products are suitable for their intended application. However, as stated above, they are not a long term solution and have some disadvantages. In fact, where copper was used on a lake over a number of years, they saw the need for increasingly higher doses to achieve the same desired effects. And the longer it is used, the greater the chance for the buildup to cause negative effects.
These are just two of the options being investigated. Their advantages and disadvantages will be compared with the others. Then, in conjunction with the results of the Nutrient Budget, and the advice of experts, we will work to develop both short and long term plans for our lake.
Be Lake Responsible