Algae in the Highland Lakes
Freshwater algae and cyanobacteria
Freshwater algae play an important role in aquatic ecosystems. Most algae are harmless, but some species (notably cyanobacteria, also called blue-green algae) can on occasion produce toxins that can be dangerous to animals and people. These events are known as harmful algal blooms, or HABs, when they occur suspended in the water column. When these events occur as algal mats, they are referred to as harmful algal proliferations, or HAPs.
Current harmful algae status in the Highland Lakes
In late February 2021, LCRA detected cyanotoxin in algal material along the shoreline on the east side of Hudson Bend in Lake Travis. This toxin is suspected to be the cause of several dogs getting ill and dying after playing in the lake in this area.LCRA is continuing to conduct tests on water and algae throughout the Highland Lakes. We recommend treating all algae as if it could be toxic, and to avoid contact with all algae in any of the Highland Lakes.
Here are updates on LCRA testing:
Blue-green algae or cyanobacteria naturally occur in water bodies throughout Texas, including those in the lower Colorado River basin. Algae can occur year-round, but they thrive during the hot summer months. It is impossible to tell whether blue-green algae are 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 or if blue-green algae will produce toxins, but toxin production in general is usually triggered when environmental conditions include excess nutrients (nitrogen and phosphorus); warm water temperatures; calm, stagnant or low-flow conditions; and ample sunlight. Harmful algae may only last a few hours or can persist for several weeks depending on weather conditions and characteristics of the waterbody.
The name blue-green algae can be somewhat misleading in the identification of cyanobacteria. Blue-green algae are most commonly blue/green, dark green, brown and black. They can make water appear as swirls of green paint, green pea soup or floating mats of what may look like moss or scum. Blue-green algae can also be intermixed with other algae that do not produce toxins (i.e., green algae and diatoms).
As part of LCRA’s water quality monitoring program, LCRA routinely monitors the Highland Lakes for harmful algae. When harmful algae are detected, LCRA conducts scientific testing to determine whether the algae are producing toxins.
Exposure to harmful algae
People and pets can be exposed to harmful algae toxins through direct skin contact from swimming and other recreational activities or ingesting water or food contaminated with harmful algae toxins.
Harmful algae 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 think you are experiencing symptoms related to exposure to harmful algae, 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 are often in shallow 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.
Drinking water supplies
Utility operators are responsible for testing and treatment to remove harmful algae toxins to acceptable federal regulatory guideline limits for public water supply uses.
Minimizing risk of exposure
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 and their pets 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.
- Avoid areas with algae or areas that are stagnant.
- If possible, keep your dog leashed near shorelines.
- Don’t let dogs consume lake water, algal material or other shoreline debris.
- Don’t let dogs lick their fur or paws after getting out of the water.
- Rinse your dog after contact with lake water.
- If your dog becomes sick after swimming, take your dog to a veterinarian immediately.
Help minimize growth and spread of harmful algae
Once harmful algae appears, there are few options besides letting it run its natural course. Chemical treatment methods such as algaecides are not recommended during a bloom or proliferation and can contribute to low dissolved oxygen levels and poor water quality, potentially making the harmful algae grow even more.
Algae thrive in shallow water 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.