Contact and General Information
If you think you are experiencing symptoms related
to exposure to blue-green algae (e.g., stomach cramps, diarrhea, vomiting, headache,
fever, muscle weakness, difficulty breathing), contact your doctor or the Wisconsin Poison Center (800-222-1222) right away.
If your pet displays symptoms such as seizures, vomiting,
or diarrhea after contact with surface water, contact your veterinarian right away.
To report a case with potential health effects caused by blue-green algae, visit
the Department of Health Services [exit DNR], or contact the Bureau of Environmental
and Occupational Health at 608-266-1120.
Swimming advisory levels have been developed by the United States Environmental Protection Agency [exit DNR]
for the toxins microcystin (8 µg/L) and cylindrospermopsin (15 µg/L)
and may be used by local health departments as the basis for issuing advisories or closing public beaches.
Most local health departments in Wisconsin do not have the capacity to monitor blue-green algae toxins at public beaches, so treat any accumulation of blue-green algae with caution. When in doubt, stay out!
For more information about contacting your local health department,
check the Department of Health Services
Web site [exit DNR].
If you are (or your local community is) interested in collecting samples for analysis,
please contact the Wisconsin State Laboratory of Hygiene at (800)442-4618.
The Wisconsin Department of Natural Resources is not currently conducting any routine
monitoring for blue-green algae or blue-green algal toxins.
What are blue-green algae?
Blue-green algae, also known as Cyanobacteria, are a group of photosynthetic bacteria
that many people refer to as "pond scum." Blue-green algae are most often blue-green
in color, but can also be blue, green, reddish-purple, or brown. Blue-green algae
generally grow in lakes, ponds, and slow-moving streams when the water is warm and
enriched with nutrients like phosphorus or nitrogen.
When environmental conditions are just right, blue-green algae can grow very quickly
in number. Most species are buoyant and will float to the surface, where they form
scum layers or floating mats. When this happens, we call this a "blue-green algae
bloom." In Wisconsin, blue-green algae blooms generally occur between mid-June and
late September, although in rare instances, blooms have been observed in winter,
even under the ice.
Many different species of blue-green algae occur in Wisconsin waters, but the most
commonly detected include Anabaena sp., Aphanizomenon sp., Microcystis
sp., and Planktothrix sp. It is not always the same species that blooms
in a given waterbody, and the dominant species present can change over the course
of the season.
How do blue-green algae differ from true algae?
Blue-green algae, like true algae, make up a portion of the phytoplankton in many
water bodies. However, blue-green algae are generally not eaten by other aquatic
organisms, and thus are not an important part of the food chain. True algae (e.g.,
green algae) are very important to the food chain. They are known as "primary producers",
a name given to living organisms that can convert sunlight and inorganic chemicals
into usable energy for other living organisms. Most algae are microscopic and serve
as the main supply of "high energy" food for larger organisms like zooplankton,
which in turn are eaten by small fish. Small fish are then eaten by larger fish,
and both small and large fish are eaten by mammals, raptors, and people.
Green algae, shown here [PDF], can also bloom at nuisance levels and may be mistaken for blue-green algae.
What are the concerns associated with blue-green algae?
Concerns associated with blue-green algae include discolored water, reduced light
penetration, taste and odor problems, dissolved oxygen depletions during die-off,
and toxin production. Discolored water is an aesthetic issue, but when blue-green
algae reach bloom densities, they can actually reduce light penetration, which can
adversely affect other aquatic organisms both directly (e.g., other phytoplankton
and aquatic plants) and indirectly (e.g., zooplankton and fish that depend on phytoplankton
and plants). Blue-green algae blooms can be quite smelly, and though it is recommended
that people never drink raw water, blue-green algae have been known to affect the
taste of drinking water that comes from surface waters experiencing a bloom. Here
in Wisconsin, most of the state relies on groundwater, rather than surface water,
for drinking water. When a blue-green algae bloom dies off, the blue-green algae
cells sink and are broken down by microbes. This breakdown process requires oxygen
and can create a biological oxygen demand. Increases in biological oxygen demand
result in decreases in oxygen concentration in the water, and this can adversely
affect fish and other aquatic life, and can even result in fish kills.
Blue-green algal toxins are naturally produced chemical compounds that sometimes
are produced inside the cells of certain species of blue-green algae. These chemicals
are not produced all of the time and there is no easy way to tell when blue-green
algae are producing them and when they are not. When the cells are broken open,
the toxins may be released. Sometimes this occurs when the cells die off naturally
and they break open as they sink and decay in a lake or pond. Cells may also be
broken open when the water is treated with chemicals meant to kill algae, and when
cells are swallowed and mixed with digestive acids in the stomachs of people or
animals. The only way to be sure if the toxins are present is to have water samples
analyzed in a laboratory using sophisticated equipment.
Are blue-green algae blooms a new problem?
No. Fossil evidence suggests that blue-green algae have been around for millions
of years. Scientists have recorded blue-green algae blooms dating back to the 12th
century and they have documented the toxic effects to livestock for more than 100
years. However, it is possible that the frequency and duration of blooms are increasing
in some Wisconsin waters as a result of increased nutrient concentrations. Nutrients,
particularly phosphorus and nitrogen, can be carried into water bodies as a result
of many human activities, including agriculture, discharge of untreated sewage,
and use of phosphorus-based fertilizers and detergents.
What is Cylindro and how is it different?
Cylindrospermopsis raciborskii, also referred to as "Cylindro," is a blue-green
algal species that is not native to Wisconsin. Recent reviews of archived samples
by DNR scientists have shown that Cylindro has been present in some southern Wisconsin
lakes dating back to the early 1980s. It is likely that migratory waterfowl brought
this algae to Wisconsin and other Midwestern states. In lakes where Cylindro has
been detected, blooms typically occur any time between late July and late September.
Cylindro is different from many other blue-green algae in that it does not typically
float to the surface to form scums. Thus, it can be difficult to see a bloom of
this species. Cylindro is capable of producing more than one toxin, including cylindrospermopsin,
which can affect the liver. However, to date, cylindrospermopsin has not been detected
in any Wisconsin waters.
Why do blooms sometimes appear overnight?
Even if you can't see blue-green algae floating on the surface of the water, that
doesn't mean they aren't there. Blue-green algae can be suspended at various depths
in the water, and their location depends on a number of factors. The most important
of these are light and nutrients (phosphorus and nitrogen). Many species of blue-green
algae have evolved to be able to control their buoyancy as the availability of light
and nutrients change with the time of day and local weather conditions. At night,
when there is no light, cells are unable to adjust their buoyancy and often float
to the surface, forming a surface scum. So this scum can literally appear overnight
and may linger until wind and waves scatter the cells throughout the water body.
Should I get treat a blue-green algae bloom with a chemical to get rid of it?
No. Treatment of a surface water that is experiencing a blue-green algae bloom with
an herbicide or algaecide may kill the blue-green algae, but any toxin(s) contained
in the cells will be released at once, resulting in a slug of toxin(s) in the water.
So while the bloom may no longer be visible, toxin(s) may be present for some period
of time following treatment. It is best to stay out of a water experiencing a bloom
and wait for the bloom to dissipate on its own.
What can be done to reduce the frequency and intensity of blue-green algae blooms?
There are no quick or easy remedies for the control of blue-green algae once they
appear in a lake or pond. Reducing the amount of nutrients that wash into our lakes
and ponds will eventually reduce the frequency and intensity of blue-green algae
blooms, but it may take a long time and a lot of community involvement to effectively
change the nutrient concentrations in a water body. This is because there may still
be large amounts of nutrients in the sediment at the bottom that may continue to
serve as food for the blue-green algae.
Regulatory agencies like the Wisconsin Departments of Natural Resources and Agriculture,
Trade, and Consumer Protection are working with communities around the state to
reduce stormwater runoff, and to encourage agricultural practices that reduce soil
erosion while maintaining high crop yields. Locally, landowners and interested citizens
can help minimize the problems associated with algal blooms by working together
with partners in their watershed to reduce the amount of nutrients that reach nearby
lakes, streams, and ponds. You can help reduce nutrient concentrations by promoting
the following practices in your community:
- Use lawn fertilizers only where truly needed
- Prevent yard debris (e.g., leaves, grass clippings, etc.) from washing into storm
- Support local ordinances that require silt curtains for residential and commercial
- Plant and maintain vegetative buffer strips along shorelines of lakes, ponds and
streams. Note: Native plants are much more effective at filtering runoff than the
typical grass species found on residential lawns.
Has the Wisconsin Department of Natural Resources conducted any monitoring for blue-green
The WI DNR conducted a two-year study to investigate the frequency, severity, and
duration of blue-green algae blooms, including information on which species of blue-green
algae are present over the course of the summer. We also looked for the presence
and concentrations of specific toxins: anatoxin-a (a neurotoxin), microcystin-LR
(a hepatotoxin), and cylindrospermopsin (a cytotoxin). Samples were (for the most
part) collected from five lakes in each of five regions, five times over the course
of each summer (2004 and 2005). Samples were also collected from eight ponds in
the south central region of the State. It is important to note that we chose to
sample sites where blue-green algae blooms had occurred in the past or where they
could potentially occur, based on nutrient concentrations. Therefore, this was not
a random sample of lakes and ponds meant to represent all lakes and ponds in Wisconsin.
Also, unlike the beach monitoring study for bacteria , this study was not designed
to provide real-time information on the presence of blue-green algae or blue-green
algal toxins, and only a limited number of surface waters could be monitored in
each region of the state. However, when DNR received information from the State
Laboratory of Hygiene on the presence of high counts of blue-green algae or on the
presence of blue-green algal toxins, this information was shared with the local
public health agency. Only the Department of Health and Family Services or the local
public health agency has the authority to close a beach.
The total number of samples collected in the statewide monitoring study was 187
in 2004, and 194 in 2005. Blue-green algae were present in 74% of all samples collected
in both 2004 and 2005 (again, samples were collected from sites where we believed
the potential for blooms was high). Blooms occurred in all regions of the state,
with the biggest "hot spots" in the west central and south central regions. Species
of blue-green algae most commonly detected included Anabaena sp., Aphanizomenon
sp., Microcystis sp., and Planktothrix sp. Alerts were sent out
to local public health agencies when concentrations of blue-green algae likely exceeded
the World Health Organization (WHO) guideline of 100,000 cells/mL. This concentration
represents a "moderate risk to human health." The total number of alerts sent out
was 33 in 2004 and 42 in 2005.
A subset of the total number of samples collected was analyzed for toxins at the
end of each summer (45 samples in 2004, and 34 samples in 2005). Microcystin-LR
(a hepatotoxin) was the toxin detected most frequently and in the highest concentrations.
This toxin was detected in the northern, south central, and west central regions
of the state. The toxin anatoxin-a (a neurotoxin) was detected in samples collected
in the northern and south central regions, and its presence was associated with
a dog death in 2004. The toxin cylindrospermopsin was never detected.