Algae in the Highland Lakes

Algae provide food, oxygen and habitat for aquatic life. There are many types of algae found in the Highland Lakes. One type, called cyanobacteria (or blue-green algae), can at times produce toxins dangerous to people and pets. People and pets should avoid algae in the Highland Lakes to minimize the risk of coming in contact with cyanobacteria.

Examples of cyanobacteria
Testing for toxins
Tips to stay safe
Health risks of cyanobacteria

Algae vs cyanobacteria

Cyanobacteria is one of the earliest forms of life. It is commonly called “blue-green algae” but is technically a type of bacteria. Cyanobacteria can begin producing toxins, called cyanotoxins, at any time, and the toxins cannot be detected by sight, smell or touch — only scientific testing can confirm their presence.

What to look for

Cyanobacteria in the Highland Lakes appear most commonly as floating mats resembling moss or scum. Cyanobacteria is most common in hot summer months when water is warm, nutrient-rich and stagnant. The photos below show common forms of cyanobacteria in the Highland Lakes.

People and pets should avoid any form of algae, because it is difficult to distinguish between potentially harmful cyanobacteria and other types of harmless algae.

Testing for toxins

LCRA regularly monitors water samples for cyanotoxins in lakes Buchanan, Inks, LBJ, Marble Falls, Travis, Bastrop and Fayette. The testing has not detected cyanotoxins in water samples at levels that would be harmful to humans or pets. However in past years, there have been toxins found in the algae itself that could be harmful if any cyanobacteria was ingested. Because cyanobacteria can begin producing toxins at any time, people and pets should avoid algae and floating cyanobacteria mats.

The City of Austin monitors algae in Lake Austin, Lady Bird Lake and Lake Walter E. Long.

Stay safe

Natural bodies of water such as the Highland Lakes are not chlorinated or disinfected, and there is always a risk of contact with bacteria or other toxins in the lakes. Water quality conditions can change frequently and can vary from one part of a lake to another. LCRA recommends lake visitors:

• Avoid direct contact with algae and cyanobacteria mats. See examples of cyanobacteria.
• Keep pets from drinking lake water or licking their fur after swimming.
• Provide clean drinking water for pets near the lake.

Health risks

People and pets can be exposed to cyanotoxins through direct skin contact or ingesting water or food contaminated with the toxins. People and pets should avoid contact with algae and cyanobacteria floating mats in the Highland Lakes.

Pets: Dogs are especially at risk through ingestion. Symptoms can appear within minutes and include vomiting, seizures, and in severe cases, death. Rinse pets after lake contact and see a vet immediately if they become ill. If you believe your dog may have come in contact with toxic algae in the Highland Lakes, please report it to LCRA through Contact LCRA.

People: Skin/eye irritation, rashes, and if large amounts of water contaminated with toxins are ingested, nausea, vomiting, dizziness or numbness. If you think you are experiencing symptoms related to exposure to cyanotoxins, call your doctor or a poison control center immediately.

Reduce algae growth and cyanobacteria mats

Once algae or cyanobacteria mats appear, there are few options besides letting it run its natural course.

Algae growth and cyanobacteria blooms are often caused by excessive nutrients in the water. Ways to reduce nutrients in the water:

• Pick up pet waste and limit fertilizer use.
• Keep yard waste out of waterways.
• Maintain native plant buffers along shorelines.
• Inspect septic systems every 3–5 years.
• Use silt fences, containment barriers and other best management practices at residential and commercial construction sites to prevent runoff.

See information on managing nuisance aquatic vegetation.