What is Blue-Green Algae?
Blue-green algae, also known as cyanobacteria, are
primitive life forms closely related to bacteria. Blue-green algae can be found
in water bodies worldwide, including those throughout Washington State.
Blue-green algae contain photosynthetic pigments similar to those found in algae
and plants. They may appear as single cells or groups of cells. Colonies may
clump together on the water's surface to form a surface scum, which can cause
water quality problems in lakes.
Toxic Blue-Green Algae Blooms
most commonly occur in the warmer months, when light,
temperature and nutrients in the water are optimal for
growth, however blooms can occur at any time of year.
Nutrient rich water may support rapid growth of
cyanobacteria, turning the lake green or blue green in
just a few days. Many species float to the surface and
form a film or scum that can be several inches thick. It
may be mistaken for a paint spill. The bloom may
disappear after one to two weeks but if conditions are
right, another bloom can occur and quickly replace the
previous one and continue for several months.
Not all blooms are toxic but some blue green algae
produce nerve (neurotoxins), liver (hepatotoxins) as well as toxins that affect
the skin and gastrointestinal tract.
Toxic cyanobacterial blooms have been increasing in
Washington lakes over the last 25 years. Environmental factors leading to toxin
production are not well understood however it is more likely that toxins are in
harmful concentrations during blooms. Signs that a bloom is toxic may be large
numbers of dead fish, waterfowl, or other animals within or around a body of
water. Animals found dead may have algae around the mouth or on the feet and
legs, indicating possible ingestion of and contact with a toxic bloom.
Only laboratory tests can determine whether a blue-green algae bloom is toxic.
Who is at risk?
Blue green blooms can be a human health concern. Exposure to cyanobacteria
and cyanobacterial toxins can occur through swimming or drinking water where
cyanobacteria are present. You can also be exposed by breathing air that contains
cyanobacterial cells or toxins. Wind surfing, jet-skiing, boating, or watering lawns
are activities where this might occur. Children usually weigh less than
adults, so a smaller amount of the toxin may make them sick and the toxin may
affect a child's
liver or central nervous system more than it would an adults. Also, children may be at greater risk than adults because
they may not be aware of any health risks due to a cyanobacterial bloom and may swallow
water accidentally while swimming.
People fishing may be at risk. Microcystins can
accumulate in fish tissues, especially in the viscera (liver, kidneys, etc.). Concentrations
in the tissues would depend on the bloom severity where the fish was caught.
Animals are also sensitive to cyanobacterial toxins. Pets and wildlife are likely
to ingest algae when they drink water from a lake or pond with cyanobacteria. If toxins
are being produced at the time animals drink the water, the animals can become very ill
and even die.
Dogs can be exposed to toxins by licking cyanobacteria from their fur after
swimming. Donít let pets or livestock swim or drink in areas where there is a scum
or mat of algae on the water. If they do swim in such areas, rinse them off as soon
as you can.
Symptoms of exposure to toxins
Swimmers and water skiers may become ill after
contacting water containing toxic blue green algae. It is rare, but humans may
experience stomach pain, vomiting, diarrhea. People may develop an allergic
reaction such as skin rash, hives, itchy eyes and throat.
Long term exposure has been shown to promote liver
tumors in animals. Therefore, people and animals should not drink water from a
source with a blue green algae bloom. There have been confirmed pet and wildlife
deaths from exposure to toxic blue green algae in Washington lakes, but there
are no confirmed deaths of humans from algal toxins worldwide.
For pets, symptoms of exposure to blue green algae
toxins include loss of appetite, vomiting, weakness, seizures, difficulty
breathing and convulsions. Neurological symptoms, including salivation, can
appear within 15 to 20 minutes of exposure. If your animals show any of these
symptoms, seek veterinary advice. Be sure to tell your veterinarian that your
animal may have come into contact with cyanobacterial toxins.
Following are steps to take to limit your risk of
exposure to cyanobacteria:
- Avoid swimming, wading, wind surfing and water-skiing in waterbodies
where cyanobacterial blooms are present.
- Avoid drinking untreated surface water.
- Use caution when considering consumption of fish caught in a water body
where major cyanobacterial blooms occur. Before eating, remove the internal
organs, which may contain more of the algae/toxin.
- Keep pets and livestock out of waterbodies where cyanobacterial blooms
- Avoid areas of scum when boating
Volunteer for Lake Watch
Thurston County is looking for volunteers to help
"watch" local lakes for algae blooms. Volunteers
activities may include:
- Contacting us when you see an algae bloom.
- Taking samples and delivering them to our office in
- Posting warning signs.
- Distributing toxic algae alerts to your neighbors.
To become a Lake Watch Volunteer, you can either
print, fill out and send us the
sign up form or
you can enter your information and submit
the form electronically.
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