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.

Return to Water School to learn more about water!




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.

If you have questions about a post or would like additional information, please contact us or call 888-922-6272.

mission minerals quality direct re-use PAM emergency use costs tributary releases salinity lake levels subsidence district electricity water code hydropower insurance watershed recreation drought spring pollutants riparian TCEQ potable corps of engineers impound lawn septic system camping hydrilla water supply system biosolids gage water use parasite calcium gate gas river lakes water planning permit authority golden algae inland acre-feet precipitation mitigation soil main stem environmental farming streamflow storage industrial fertilizer municipal bay wetland granbury filter turbidity riverine golden algea volume water sanitation supply algae taste canoe watercourse fishing hydrology contaminants governance bed and banks aerobic industry environment drilling basin agricultural jobs mainstem invasive plants evaporation estuary brackish E. coli conservation sewage marsh wetlands legislation channel use acre-foot monitor corps cfs sediment electric companies bottled water map subsidence smell meta tag hydrologic cycle inundated surface water medicine water treatment drinking water flood pool xeriscape pharmaceuticals dissolved solids planning ground water measure water quality aquifer depth allens creek reservoir solids limestone agriculture Board habitat boating salt reservoirs hunting gulf canoeing subwatershed landscaping water clarity dam wastewater employment fork appropriation fish kill effluent USGS mgd rights contract classification consumption sludge reservoir groundwater lake well wildlife water rights flood flood control lake kayak spillway possum kingdom rain E coli chlorine septic oxygen treatment indirect re-use chlorides water plants beneficial use speaker organic stream water cycle runoff clarity anaerobic maps infection streamflow lake level dock climate