Harmful Algal Blooms
Freshwater algal blooms and cyanobacteria
Freshwater algae plays an important role in aquatic ecosystems. Most algae is harmless, but some species (notably blue-green algae, or cyanobacteria) can on occasion produce toxins known as harmful algal blooms, or HABs, that can be dangerous to people and animals.
Current HAB status in the Highland Lakes
To date, LCRA is not aware of any active toxic algal blooms in the Highland Lakes. If a toxic bloom is identified, LCRA will post locations on this webpage and will notify any applicable local jurisdictions.
Blue-green algae naturally occur in water bodies throughout the Colorado River basin. They thrive during the hot summer months, but typically die off as water temperatures begin to cool in October. It is impossible to tell whether blue-green algae is producing toxins by look, touch or smell, so scientific testing is required to determine if toxins are present.
It is difficult to predict precisely when HABs will occur, but freshwater HABs are usually triggered when environmental conditions include excess nutrients (nitrogen and phosphorus); warm water temperatures; calm, stagnant or low-flow conditions; and ample sunlight. HABs may only last a few hours or can persist for several weeks depending on weather conditions and characteristics of the waterbody.
Blue-green algae can make water appear as swirls of green paint, green pea soup or floating mats of scum, and is sometimes accompanied by a foul odor.
As part of LCRA’s water quality monitoring program, LCRA routinely monitors the Highland Lakes for blue-green algae. When a blue-green algae bloom is identified, LCRA conducts scientific testing to determine whether the bloom is emitting toxins.
Swimming in natural water bodies such as the Highland Lakes always carries risks. Unlike swimming pools, natural water bodies are not chlorinated or disinfected. People who enter the water do so at their own risk. Water quality conditions can change frequently, and can vary from one part of a lake to another.
The best way to protect you and your pets from algal toxins is to avoid all direct contact with algae and algae blooms.
Exposure to HABs
People and pets can be exposed to HAB toxins through direct skin contact from swimming and other recreational activities, ingesting water or food contaminated with HAB toxins, or inhaling airborne droplets that contain HAB toxins.
HAB toxins can cause skin and eye irritation or rashes. Severe reactions can occur when large amounts of water are ingested, and can range from diarrhea, cramps and vomiting to fainting, dizziness and numbness, or tingling in lips, fingers and toes. If you swallow water from a HAB or think you are experiencing symptoms related to exposure to an HAB, call your doctor or a poison control center. For more information, visit the Centers for Disease Control and Prevention HAB-Associated Illness webpage.
Dogs are especially susceptible to algae toxins because they often swallow water while swimming, playing, retrieving and grooming. Do not let dogs drink or play in areas with visible algal blooms, and never let them eat or lick algal scum off the water or their fur. Animals can experience symptoms within minutes of exposure, including drooling, vomiting, diarrhea, weakness, difficulty breathing, seizures, and even death. If your pet comes in contact with a HAB, rinse them with clean, fresh water and call a veterinarian immediately if symptoms occur.
Other exposure risks
- Aquatic and amphibious life and wildlife can suffer illness or death from HABs. Do not eat fish, shellfish or wild game from areas where there is a suspected HAB.
- Livestock also can be sickened or killed by ingesting toxins from HABs. Best preventative practices include fencing off access to surface water streams or impoundments during peak HAB seasons and providing alternative sources of fresh water.
Drinking water supplies
Utility operators are responsible for testing and treatment to remove HAB toxins to acceptable federal regulatory guideline limits for public water supply uses.
Help minimize growth and spread of HABs
Once a bloom appears, there are few options besides letting it run its natural course. Chemical treatment methods such as algaecides are not recommended during a bloom and can contribute to low dissolved oxygen levels and poor water quality, potentially making the bloom grow even more.
Algae thrive in warm environments with plenty of nutrients. To help reduce man-made sources of nutrients:
- Pick up and properly dispose of pet waste.
- Reduce the use of fertilizer on lawns. Most established lawns do not need additional phosphorus to be healthy.
- Do not dump lawn clippings, leaves or other yard waste into storm drains, creek beds, lakes or other waterways.
- Have your septic system inspected and pumped at least every three to five years to help ensure it operates properly.
- Use silt fences, containment barriers and other best management practices at residential and commercial construction sites to prevent runoff of nutrient-laden sediment.
- Plant and maintain vegetative buffer strips along shorelines of lakes, ponds and streams. Native plants are much more effective at filtering runoff than the typical grass species found on residential lawns.