Blue-green algae blooms not detected in BRA reservoirs

Blue-green algae blooms not detected in BRA reservoirs


Concerns over the potential for a toxic algae bloom are spreading throughout the country.

Blue-green algae is believed to behind the deaths of several dogs throughout the United States, including several from the Austin area.

Here is what you need to know about blue-green algae in the Brazos River basin:

Blue-green algae can exist in all freshwater, said Jenna Olson, Brazos River Authority Environmental Programs Coordinator. Though blue-green algae is common to find in freshwater bodies, green algae is the dominant algae in the reservoirs located within the Brazos River basin.

Though blue-green algae are believed to be tied to the deaths of several pets, not all blue-green algae is toxic.

“In fact, some is consumed as dietary health supplements such as Spirolina. Even the toxic varieties typically have to be in a high concentration to cause toxicity problems,” Olson said.

There are more than 2,600 species of blue-green algae, or cyanbacteria. More than 50 of those species have shown to produce toxins that can be harmful to vertebrates.

Blue-green algal blooms, which become toxic, have not ever been detected in any of the BRA owned and operated reservoirs.

Common toxin-producing species that form blooms include members of the genera Microcystis, Dolichospermum (formerly known as Anabaena), Sphaerospermopsis, Planktothrix (Oscillatoria), Cylindrospermopsis, Aphanizomenon, Cuspidothrix, Chrysosporum, Plectonema (Lyngbya), Gloeotrichia, and Nodularia.

Toxic blooms have been linked to hotter weather.

“Abundant sunshine fueling photosynthesis supports algal blooms as well,” Olson said. “Higher water temperatures are optimal for blue-green algal growth and blue-greens generally do not persist through the winter months due to low water temperatures.”

If you’re on a water body, you will be able to tell there is an algal bloom; however, you wouldn’t be able to tell which type of algae it is unless you look at it under a microscope. Experts advise that if you see water with a “pea-soup” color and consistency, avoid it.

“Non-flowing water is a better habitat for supporting an algal bloom,” Olson said.

If you’re out on a BRA reservoir and notice water that appears green and thick, don’t swim or let your pet go into the area. If you are concerned, please contact the BRA at (254) 761-3100 with the location.

The BRA regularly tests for pH, specific conductance, dissolved oxygen, chloride, sulfate, E. coli levels and much more.

For more, see the table below.



Specific Conductance

Specific conductance is a measure of the waterbody’s ability to conduct electricity and indicates the approximate levels of dissolved salts, such as chloride, sulfate and sodium in the stream.


Most aquatic life is adapted to live within a narrow pH range. Different organisms can live at and adjust to differing pH ranges, but all fish die if pH is below four (the acidity of orange juice) or above 12 (the pH of ammonia).

Dissolved Oxygen


Organisms that live in the water need oxygen to live. Where DO is low, organisms may not have sufficient oxygen to survive.


Turbidity is a measure of the water clarity or light transmitting properties. Increases in turbidity are caused by suspended and colloidal matter such as clay, silt, finely divided organic and inorganic matter, plankton and other microscopic organisms.


Chloride is an essential element for maintaining normal physiological functions in all organisms. Elevated chloride concentrations can disrupt osmotic pressure, water balance and acid/base balances in aquatic organisms which can adversely affect survival, growth and/or reproduction.


Effects of high sulfate levels in the environment have not been fully documented. However, sulfate contamination may contribute to the decline of native plants by altering chemical conditions in the sediment.

Total Dissolved

Solids  (TDS)

High total dissolved solids may affect the aesthetic quality of the water, interfere with washing clothes and corrode plumbing fixtures. High total dissolved solids in the environment can also affect the permeability of ions in aquatic organisms.

Total Suspended

Solids (TSS)

Suspended solids increase turbidity which reduces light penetration and decreases the production of oxygen by plants. They can also clog fish gills. Eventually, the suspended solids settle to the bottom of the stream or lake, creating sediment. Excessive sediment in the water column can also reduce growth of algae and can transport other contaminants such as nutrients and bacteria.  Habitat for aquatic organisms can also be reduced.


  • Escherichia coli (E. coli)

Although certain species of bacteria may not themselves be harmful to human beings, their presence is an indicator of recent fecal matter contamination and that other pathogens dangerous to human beings may be present.


Elevated levels of ammonia in the environment can adversely affect fish and invertebrate reproductive capacity and reduce the growth of young.


  • Total Kjeldahl Nitrogen
  • Nitrite Nitrogen
  • Total Phosphorus
  • Ortho-phosphate phosphorus


Nutrients increase plant and algae growth. When plants and algae die, the bacteria that decompose them use oxygen. This reduces the dissolved oxygen in the water. High levels of nitrates and nitrites can produce nitrite toxicity, or “brown blood disease,” in fish. This disease reduces the ability of blood to transport oxygen throughout the body.

Chlorophyll a

High levels of nutrients in relatively stable waters can cause algae blooms, decrease water clarity and cause swings in dissolved oxygen and pH due to photosynthesis. This is most commonly measured using chlorophyll a concentrationsAlgal blooms can result in elevated chlorophyll a concentrations indicating an increase in nutrients that increase growth and reproduction in algal species.