INFORMATION REGARDING BLUE-GREEN ALGAE
Submitted by Gina LaLiberte
Research Scientist - Bureau of Science Services
Wisconsin Department of Natural Resources
A lot of lakes have algae, even in northern Wisconsin. Blue-green algae are in every lake and river in the state, but they don't become a problem until high nutrients (phosphorus and nitrogen) enable them to grow to nuisance levels. Lake George is eutrophic, which means it has high nutrient levels that can support the growth of algae blooms or aquatic plants or both). The upside to this, especially for the lake homeowners who like fishing, is that eutrophic lakes can support larger fish populations.
If you use common sense precautions, you can safely enjoy recreation on Lake George and any other lake.
- Choose locations without noticeably green water for swimming, because wind can concentrate blue-green algal blooms into near-shore areas. Do not swim in water that looks like "pea soup", green or blue paint, or that has a scum layer or puffy blobs floating on the surface.
- Do not boat, water ski, etc. over what looks like "pea soup", green or blue paint, or that has scum layer or puffy blobs floating on the surface (people can be exposed through inhalation).
- Do not let children play with scum layers, even from shore.
- Always offer fresh, clean water for pets to drink. Do not let pets swim in, or drink, waters experiencing blue-green algae blooms or noticeably green water.
- Always take a shower after coming into contact with any surface water (whether or not a blue-green algae bloom appears to be present, surface waters may contain other species of potentially harmful bacteria and viruses).
- Pets should be washed off immediately after swimming, before they groom.
- Always avoid swallowing untreated surface water - it may contain pathogens other than blue-green algae which could make you ill.
The Wisconsin Department Health Services as provided the following guidelines concerning fish consumption:
- Algal toxins have not shown to accumulate to acutely toxic levels in the fillet.
- Clean fish thoroughly and discard the viscera and guts, where toxins may accumulate
- Illness due to chronic exposure seems unlikely when eating North American fish
- Wash hands after handling fish caught during an algal bloom.
It's important to keep in mind that blue-green algal blooms are easily moved around in lakes by wind and currents, and thus conditions can change from hour to hour. This makes monitoring extremely challenging. The one good thing about blue-green algae is that unlike pathogens such as E.coli, you can see blue-green algae in the water and use the above precautions to protect yourself when water is noticeably green and especially when water is an opaque green similar to pea soup, or if algae are concentrated at the surface in a scum.
The main risk for illness is from ingesting blue-green algae by swallowing water of inhaling water droplets (such as while water skiing or tubing). Some people may also experience dermal irritation such as rashes from skin exposure to blue-green algae. For a good rule of thumb, if you can wade knee-deep into water (without disturbing the sediment) and cannot see your feet because the water is green and/or opaque, you should stay out. Algae cell densities are high enough that if the algae are producing toxins, you could become ill from swallowing water or inhaling water droplets, or have irritation from skin exposure. Small children and animals should always be kept away from water in these conditions. Blue-green algae can't always produce toxins and even if they can, they don't produce toxins all the time. However, you can't tell if they are producing toxins just by looking at a blom, so avoiding contact with high levels of algae is the best way to stay safe.
There's more information about blue-green algal blooms at http://dnr.wi.gov/lakes/bluegreenalgae/ (including a link to our YouTube video) and http://www.dns.wisconsin.gov/eh/bluegreenalgae/. The DHS has a pet fact sheet on their website. You can also report illnesses potentially related to blue-green algae exposure at the DHS website. If you would like to know what to look for when identifying blue-green algae, please see my Wisconsin Lakes Partnership Convention presentation here: http://www.uwsp.edu/cnr-ap/UWEXLakes/Documents/programs/convention/2014/LaLiberte-HarmfulAlgalBloomsinWIwaters.pdf.