Golden Alga in Texas

Archived News Release

Sept. 10, 2001

State Taking Steps To Combat Golden Algae

Austin, TEXAS — Like the common cold, golden algae appears to be a bug that isn't going away and, unfortunately, science has yet to find a cure. The good news is that there could be some “chicken soup” remedies to at least treat some of the symptoms while researchers explore ways to combat the naturally occurring toxin that caused significant fish kills along the Brazos River watershed this year.

Golden algae (Prymnesium parvum) were identified for the first time in Texas during a fish kill on the Pecos River in the 1980s. The brackish water toxin is believed to be responsible for fish kills in several other Texas river basins, including the Colorado, Red and Brazos. The latest outbreak — which according to state officials caused economic and ecological damage from fish kills on three north central Texas reservoirs and at a state fish hatchery — has put the toxin in the public spotlight. Although the fish kills have ended, efforts are being taken to address the potential for future outbreaks.

“It appears that we're seeing impacts from this organism in a wider area around the state and we have no reason to believe it's going away," said David Sager, Texas Parks and Wildlife's freshwater conservation branch chief. "There are no control mechanisms and not enough is known to determine if we can develop one. But, we're taking steps to address the problem.”

A committee of scientists led by TPW is putting together research projects to address management and potential control options for this alga based on discussions during a recent public workshop at Possum Kingdom Reservoir. Researchers are hoping to determine among other issues how and why golden algae occur, the potential distribution of the alga in Texas and the ecological and economic impacts from outbreaks. Fisheries biologists are currently exploring ways to control the toxin in hatcheries.

Golden algae are estuarine-based (saltwater-tolerant) organisms, according to Sager, and have been responsible for fish kills in Denmark, Great Britain, Israel, South Africa and Scotland. “This isn't all that unusual in nature, but having this alga this far inland and this widespread is a problem.”

Sager said that Texas is the only known place where the alga has affected inland waters, creating a different set of problems for freshwater fisheries managers and public stakeholders on affected water bodies. “We've found golden algae in waters where there's a salinity content, like in West Texas, but what we're seeing now is that this organism can move into fresher environs than it has in Europe or elsewhere,” he said. Red tide (Gymnodinium breve) algal blooms occur periodically along the Texas coast but affect the fishery for a relatively short time and then disappear. Golden algae aren't going away, and can cause significant damage when they bloom, Sager said.

Golden algae may exist in small quantities year-round throughout the Brazos River watershed from Throckmorton to the Lake Whitney area, according to TPW studies. Gary Saul, TPW hatcheries chief, says the toxin has been found in hatchery ponds even after the water has been drained. “What we've learned is that even when we drain a pond, there's a resting period where the algae will remain in the mud, and when we add water back, we still have the algae,” he said. “We have to determine when and how to treat the ponds to effectively control this organism, and it's all experimental right now.”

The pond culture industry in Israel has found aggressive treatment with ammonia can reduce a golden alga toxic bloom, allowing restocking of the culture ponds, said Dave Sager, TPW freshwater conservation branch chief. While the treatment might be effective for farm ponds and hatcheries, it would not be cost-effective or practical for large water bodies. “In addition to the cost and problems with treating such large reservoirs, the concentrations of ammonia required would have adverse impacts on other organisms in the aquatic ecosystems,” Sager noted. “The cure could be as bad as the problem.”

Large concentrations of golden algae (blooms) cause water discoloration ranging from yellow to coppery-brown and can often be toxic to fish, said Sager. The toxins affect the fish's gill-breathing system, limiting their ability to take in oxygen and, as with red tide, death occurs from asphyxiation.

Red tide can cause respiratory difficulty in humans, but, according to the Texas Department of Health, anecdotal evidence has shown no human health risks associated with golden algae. Livestock have been observed drinking from rivers during active golden algae blooms without apparent harm.

This year, golden algae affected fisheries at Possum Kingdom Reservoir, Lake Granbury and Lake Whitney, with a loss of 600,000 fish valued at $650,000, according to TPW Kills and Spills Team estimates. Additionally, the toxic algae wiped out TPW's yearly production of striped bass when it got into the Dundee Hatchery's water source. Fisheries managers had to obtain striped bass from other states to replenish stocks lost to golden algae.

TPW is working to avoid a repeat next year, said Saul. “We're conducting tests right now to protect the fry when we put them in our grow-out ponds. We need to be able to treat the water in the ponds and either kill the algae or hopefully render the toxin harmless.”

Saul said he expects the Dundee State Fish Hatchery to be back in full production next year, and protocols are being developed to minimize the risk of losing production to a golden algae outbreak. “We'll also have Possum Kingdom (State Fish Hatchery) back in operation next year. It was closed this year for renovations, but because all our hatcheries are running at capacity, we don't have many options if the algae can't be controlled," he explained. "One alternative — if we're not able to keep the fry alive in our ponds until they become fingerlings — is to stock the fry directly into lakes. We end up stocking more fish that way, but survival isn't as great as when you put in fingerlings."

"Unlike in the hatchery ponds, at present there are no cost-effective or efficient methods for control in a watershed," Sager said. "We will try to assess the fisheries and restock or manage those lakes to try and overcome the impacts. Hopefully, the future research will develop new control and management options."

As a result of the public workshop, researchers will seek assistance from their red tide counterparts on the Harmful Algal Bloom Committee, which was originally formed to discuss red tide algal blooms and other marine toxic algae. The Harmful Algal Bloom Committee is a component of the legislatively formed interagency Toxic Substances Coordinating Committee and could be helpful in bringing other state, federal and academic participants to the table, said Sager.

"This issue is important to our constituents around Possum Kingdom Reservoir and to the overall health of the affected resources," said Larry McKinney, TPW senior director for aquatic resources. "The workshop was a positive first step in finding solutions to this problem."

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Take Action
  • Report Kills - If you see a fish kill or suspect golden alga, contact TPWD's 24-hour communications centers at 512-389-4848 (Austin).
  • Get the Facts - TPWD has collaborated with the Texas Commission on Environmental Quality and other entities to produce a golden alga information card. Download a PDF from the TCEQ website or request a free hard copy from TPWD at