Due to the drought and unusually warm weather conditions, toxic blooms of blue-green algae and other water-quality issues are occurring more frequently in the East Bay Regional Park District and elsewhere. We monitor our lakes and shorelines regularly, and post warnings and closures when appropriate. Here’s a current update of which lakes and shorelines are affected:
- Lake Temescal contains toxic algae and is closed for swimming.
- Quarry Lakes contains toxic algae and is closed for swimming.
- Lake Chabot contains toxic algae and is closed for swimming regardless, but dogs should not go in the water.
- Shinn Pond contains toxic algae and is closed for swimming regardless, but dogs should not go in the water.
- Crown Beach may contain the swimmer’s itch parasite. Swimmers should rinse and towel dry thoroughly after being in the water.
The Park District encourages visitors who wish to enjoy water activities to visit these other popular lakes, beaches, lagoons and pools: Lake Anza at Tilden Regional Park in Berkeley, Cull Canyon in Castro Valley, Contra Loma Lagoon in Antioch, Don Castro in Hayward, Del Valle Recreation Area in Livermore, and Roberts Pool at Roberts Regional Recreation Area in Oakland.
About Toxic Blue-Green Algae:
Blue-green algae are natural organisms that are present in most lakes. Certain conditions – low water levels, limited water circulation, increased heat and light, among other factors – can cause the algae to bloom and, in some cases, release toxins. The most common toxins in the algae are Anatoxin-A, a neurotoxin, and Microcystin, which affects the liver. Scientists do not know what causes the algae to become toxic.
The Park District had never before seen toxic algae blooms in its lakes but in 2014 recorded three, most likely due to the drought. The first and third toxic blooms were in Lake Temescal in Oakland, both blooms resulted in its closure for a total of about nine weeks over the summer and fall, and a second bloom was discovered in September in Lake Chabot and still remains.
Exposure to toxic algae, either through ingestion or skin contact, can cause rashes, skin and eye irritation, allergic reactions, gastrointestinal problems or, at high doses, serious illness or death, according to the California Department of Public Health. Several dog deaths around the state have been attributed to toxic algae poisoning in the past two years.
Blooms usually run their course and dissipate in a week or two, but rain storms and cold temperatures can speed up the process. At Lake Temescal, the Park District used an organic chemical called Pak 27 to control the algae. The chemical is safe for water used for drinking, swimming and fishing, and does not harm other aquatic life. The District has not used the chemical at Lake Chabot because due to the lake’s large size. The water in Lake Chabot is under the jurisdiction of the East Bay Municipal Utility District.
Swimming – by dogs or people – is not allowed at Lake Chabot. Several signs at the lake warn visitors to stay out of the water due to the algae, rinse skin with tap water after contact, and keep pets away from the water. Fish should be rinsed in tap water and the guts discarded.
Frequently asked questions:
What are blue green algae?
Blue green algae (or cyanobacteria) are a common native algal species often found in water or wet areas.
What is a blue green algae bloom?
When conditions are right, algae can rapidly build up or “bloom” on the surface of reservoirs, rivers, creeks, lagoons, lakes and ponds. The bloom can be green, blue green, white or brown, and may look like a floating layer of scum or paint and may have an unpleasant odor.
What causes blooms?
Warm, slow-moving waters that are rich in nutrients can cause algae growth. Blooms can occur at any time, but are most common in late summer or early fall.
How do I know if a bloom is toxic?
Only a few types of blue green algae are known to produce poisons. The presence of blue-green algae in a water body does not necessarily mean toxins are always present. However, identifying the presence of toxins is a difficult process and one that may involve many days to weeks before results are available. Therefore, it is prudent for recreational users to adhere to the following precautions with regard to blue-green algae blooms in East Bay Regional Park District water bodies.
Always look for the signs of an algae bloom BEFORE you enter the water or before you let your children or pets enter the water.
How dangerous is toxic algae?
If toxic algae touches your skin, or you accidentally inhale or swallow water containing the toxin during recreation, you could get a rash or an allergic reaction, or develop gastrointestinal problems. The long-term effects of these exposures are not well known, but children and pets are at greatest risk. Dogs can be exposed to particularly high levels of toxins by licking blue green algae off their fur after a swim.
What should I do if I see a bloom?
> Stay out of areas where the water has foam, scum, or mats of algae. Keep children and pets out of such areas at all times. If you or your pets swim or wade in water with algae, rinse off with fresh water as soon as possible.
> If no algal scums or mats are visible, you should still carefully watch young children and warn them not to swallow the water.
> Do not drink or cook with this water. Even if you boil or filter it, the toxins can persist.
> Do not let dogs swim in or drink from areas where you see foam, scum, or mats.
> Get medical treatment right away if you think that you or your pet might have been poisoned by blue green algae toxins.
> If you accidentally swallow water from an algae bloom and experience one or more of the following symptoms: stomach cramps, vomiting, diarrhea, and fever, you should contact your physician or seek medical treatment.
What about fishing and other activities?
Eating fish caught during a heavy bloom can pose a health risk. Always remove the guts and liver, and rinse fillets in tap water before eating the fish. Other activities near the water such as camping, picnicking, biking and hiking are safe.
Find more information at the California Department of Heath Public Health’s website.