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Harmful Algae Blooms in Clear Lake

Lake County– Public Health is urging boaters and recreational users to avoid direct contact with or use of waters containing blue-green algae (cyanobacteria) in Lake County.  The recommendation is based on the potential health risks from the algae, which is currently blooming at varying levels in all three arms of the Lake (Upper Arm, Oaks Arm, and Lower Arm).

Water monitoring is done by Big Valley Band of Pomo Indians and Elem Indian Colony.

Testing results from 8/7/18 - (“danger” level triggering warnings at 20 micrograms per liter µg/L):

Sulphur Bank Mercury Mine/SBMMEL01 with a result of 4800 µg/L - Danger Zone (Red):
Austin Park Beach/AP01 with a result of 230 µg/L - Danger Zone (Red);
Redbud Park Boat Launch/RED01 with a result of 24 µg/L - Danger Zone (Red);
Soda Bay Cove/CLV7 with a result of 13 µg/L - Warning Zone (Orange);
Cache Creek/SHADY01 with a result of 8.7 µg/L - Warning Zone (Orange);
ELEM Indian Colony/ELEM01 with a result of 3.7 µg/L - Caution Zone (Yellow):
Lakeside County Park/CP with a result of 2.9 µg/L - Caution Zone (Yellow);

HAB Map 081318

Blue-green algae can pose health risks, particularly to children and pets. We urge people to choose safe activities when visiting the Oaks Arm and parts of the Lower Arm of Clear Lake and wherever blooms are visible.  It is strongly recommended that people and their pets avoid contact with water and avoid swallowing lake water in an algae bloom area.

Recommendations from the Statewide Guidance on Cyanobacteria and Harmful Algal Blooms:

  • Take care that pets and livestock do not drink the water, swim through algae, scums or mats, or lick their fur after going in the water.  Rinse pets in clean water to remove algae from fur.
  • Avoid wading, swimming, jet or water skiing in water containing algae blooms, scums or mats.
  • Do not drink, cook or wash dishes with untreated surface water from these areas under any circumstances; common water purification techniques such as camping filters, tablets and boiling do not remove toxins.
  • People should not eat mussels or other bivalves collected from these areas.  Limit or avoid eating fish from these areas; if fish are consumed, remove the guts and liver, and rinse filets in clean drinking water.
  • Get medical treatment immediately if you think that you, your pet, or livestock might have been poisoned by blue-green algae toxins.  Be sure to alert the medical professional to the possible contact with blue-green algae.  Also, make sure to contact the local county public health department at (707) 263 - 1090.
Sulphur Banks Mercury Mine site is close to a private drinking water supply.  The Big Valley Band of Pomo Indians and Elem Indian Colony will be following up with these drinking water suppliers. The Redbud Park boat launch location is close to a drinking water supply. Sampling of drinking water at the site will occur on August 17, 2018.


What is the Problem?
Cyanotoxin are produced by bacteria called cyanobacteria.   They are an essential part of the environment that have existed for millions of year and produce oxygen.  Under certain conditions, they multiply excessively and form visible clumps that can appear as cut grass in the water or blue-green, white or brown foam, scum or mats that can float on the water’s surface and accumulate along the shoreline and boat ramp area.

On occasion, they produce toxins that can cause harmful effects in people and animals if exposed through ingestion, inhalation of aerosolized water or direct contact.  As environmental factors change, most harmful algae blooms resolve over time.   However, when cyanotoxin are known to be present, re-testing the water after it has cleared and allowing at least two weeks to pass after no toxins are found is recommended

What are the health effects?
When the toxins are ingested in large amounts they can cause:

  • Sharp, severe stomach problems like diarrhea and vomiting.
  • Liver damage that may take hours or days to show up in people or animals.
  • Numb limbs, tingling finger and toes or dizziness.

Possible health effects of animal exposure to a toxic bloom:

  • Weakness, staggering, difficulty breathing
  • Convulsions
  • Vomiting or diarrhea

Signs of a toxic bloom may include: a large number of dead fish, waterfowl or other animals, or sudden, unexplained sickness or death of a cat or dog that has been exposed. It is not possible to tell if cyanobacteria are toxic by looking at them. There is ongoing research on potential health effects of exposure to the toxins produced by some species of cyanobacteria. The California Department of Public Health evaluates any new findings and makes updates to guidance materials as necessary.

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Water Faucet
Urgent Health Advisory

Effective immediately, people on private water systems whose tap water comes from their own private intake into the lake, in the Oaks Arm and Lower Arm of Clear Lake should not drink the water.

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