There is a lot going on in the world today and the recurrent appearance of harmful algal blooms (HABs) is simply just another issue Wisconsin waterway stakeholders are not fully prepared to take on. The State of Wisconsin is blessed that it does not receive much drinking water from reservoirs (other than Lake Michigan). Plain states such as Kansas, are dealing with critical HAB issues now.
What is HAB again? Harmful Algal blooms are a not really algae at all. HABs are actually a photosynthetic type of bacteria closely resembling the visual aspects of other types of algae but only exist under the right environmental conditions. These bacteria are know as cyanobacteria (often referred to as blue-green algae). The exact chemistry has yet to be pinpointed but there are certain trends that over time have shown to favor the presence or growth trigger for HABs.
Wisconsin Department of Health Services maintains a good informational source on HABs. The WDNR also has a page here, specifically directed towards lakes.
Why is this a problem. HABs > cyanobacterial > blue-green algae or whatever term you chose to use can have exposure risks to various age groups and furthermore household pets. There is more accurate and detailed information on the links provided above, but prolonged exposure is a health risk, more to young and old, but there is no need to subject anyone to these issues if everyone does there part to keep their lakes healthy. The ever recurrent theme is tied to pursuit and maintaining of a healthy lake environment.
Many of the HAB triggers are consistent with less than ideal lake or stream conditions tied to signs of eutrophication, which will be the topic of future discussion. For right now think of it as an overabundance of available nutrients typically associated with excess phosphorus. Phosphorus is known to be a trigger for standard algae blooms, and excess aquatic biomass accumulation, both of which lead to unnecessary premature aging of lakes.
Lake aging is a natural process, but sedimentation and excess bio-accumulation speed up the process. Combating both these issues starts with responsible lake and watershed management. Working in the watershed to reduce annual loading to the lake and looking inside the lake to observe recurrent shoreline erosion and migration that might be hidden. Shoreline erosion is a silent producer of sediment and degrades habitat. Therefore working to combat these issues through responsible lake and watershed management will assist in HAB management as well. Do not make the mistake of thinking HABs are limited to lakes and reservoirs only. Streams can exhibit HAB like symptoms as well which can also end up in a lake system.