Water School

Has golden algae been found in the Brazos River basin?

Yes, golden algae is present in parts of the basin year round. However, the great majority of the time it is at such a level that it has not caused a threat to fish in a few years. 

Golden alga, or Prymnesium parvum, a naturally occurring alga that can have a devastating effect on fish, persists in small amounts throughout the year in the Brazos River basin, according to the Texas Parks and Wildlife Department

Texas is the only known place known to date that deals with golden alga inland, David Sager said in a news release. Sager previously served as Texas Parks and Wildlife Departments-freshwater conservation branch chief. Typically, golden alga affects coastal waters primarily and not freshwater. 

Golden algae is an organism that lives in surface water year-round. It is harmless to other organisms when not in bloom. However, when a bloom is triggered, the alga gives off a toxin that limits oxygen and causes the destruction of red blood cells, killing fish within its vicinity. Humans and other animals are not affected by the toxin. Since 2006, the algae has killed over 31 million fish in Texas alone. Golden algae is different from other alga types because of its persistence in the places it infects, Sager said in the news release.

“There are no hard and fast rules with golden algae," said Tiffany Malzahn, Brazos River Authority environmental and compliance manager. "Every time we think it's figured out, it does something different. It is really good at defying prediction. Most commonly, numbers in the report greater than 10,000 cells/millimeter cause concern that enough algal cells are present to cause toxic events that will impact aquatic life at the reservoir."

Common signs of golden alga are water discoloration and the sudden appearance of numerous dead fish. Toxin-affected water ranges in color from coppery-brown to yellow.   Though a great deal of study has been done in Texas since the large fish kills of 2006, researchers at TPWD have found that some treatments have been effective for ponds and small reservoirs. However, at this time, there is no means of controlling golden alga in large reservoirs and rivers. 

When a report of dead fish is confirmed in the Brazos River basin's rivers or reservoirs, TPWD's Kills and Spills Team, assisted by the BRA's team of environmentalists, travel to the scene of the die-off to investigate the cause and document the case.

Golden alga is not known to cause harm to humans. However, it is best practice to never swim near, pick up or consume dead fish. 

To report golden alga sightings or fish kills, please contact your local game warden or call the TPWD's 24-hour communications center at 512-389-4848.

To learn more about the science and history of golden alga, click here.

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The information provided on this site is intended as background on water within the Brazos River basin. There should be no expectation that this information is all encompassing, complete or in any way examines every aspect of this very complex natural resource.

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