Greenhouses and nurseries are the best places to find bright, lively wintertime flowers, however, there’s another bloom that fisheries biologists and others associated with the fishing industry in Texas would rather not have to lay eyes on. This bloom represents the spread of golden alga, a highly toxic, microscopic organism that can be lethal to all types of gill-breathers, most notably fish, but also some arthropods and amphibians.
Prymnesium parvum, which turns water a yellowish-copper color when it blooms, already has accounted for fish kills in five Texas river basins — the Canadian, Red, Brazos, Colorado and Rio Grande chains — and likely will affect others in the future.
Though the bloom, a substantial increase of the species, has killed many gilled organisms and seems to thrive in colder temperatures, no humans or other mammals have been affected by the alga.
According to TPWD reports, affected fish can recover from the early effects of the alga if they are able to swim to an area free of toxins.
Craig Bonds, the new TPWD inland fisheries division director who has spent time in several state locales as a biologist and director, previously has said golden alga’s worst effects have been noted mostly in Central and West Texas bodies of water.
“E.V. Spence (just west of Robert Lee) and some other lakes historically were good fisheries, but in the past decade they have been severely impacted by golden alga,” he said. “The lakes in the western part of the state have higher saline levels and the alga thrives in that type of environment.
“When the golden alga blooms, it creates a toxin in the water that causes fish gills to hemorrhage and they suffocate.”
Bonds has said that though golden alga has become a serious problem, it hasn’t affected wide portions of lakes it has moved into.
“The golden alga is really a brackish water-living alga,” he said. “It causes fish kills when the pH level is high and conditions are more conducive to its growth. It usually takes place in pockets and coves, not on a lakewide basis.”
Since 2001, golden alga blooms have caused more than 130 major fish kills and resulted in the loss of more than 34 million fish valued at more than $14 million. According to TPWD reports, Lake Whitney saw the largest one-day fish kill in recorded history, a 4.9 million kill in February 2005. More than 4 million fish also were killed as a result of golden alga on Lake Granbury in the winter of 2004 and spring of 2005.
One notable lake that has been hit repeatedly and seemingly rebounded every time is Possum Kingdom, a good striper fishery about 75 miles west of Fort Worth on the Brazos River. The lake had notable fish die-offs in 2001 and 2003 and had another subsequent kill of tens of thousands of fish. Whitney also was affected last year and had similar kills.
Reports show the heaviest hit to the statewide fishery occurred in 2001 at the Dundee State Fish Hatchery in the Red River Basin. The hatchery, the largest in the state, is one of two sites where TPWD produces stripers and hybrid stripers that are then stocked into lakes for anglers to catch. Stripers don’t reproduce in fresh water lakes that don’t have readily available rivers running into them like Lake Texoma, so TPWD grows fry, fingerlings and larger fish in a series of ponds.
Golden alga got into those shallow ponds and before it could be stopped or the fish moved, the organism had killed an entire year’s worth of striper production, more than 5 million fish.
It is not known whether golden alga is a native species or one that was accidentally brought to North America.
According to TPWD, Texas biologists were the first to document the occurrence of the alga in fresh water in the Western Hemisphere. Among other southern states that have been affected by golden alga are Alabama, Louisiana, Oklahoma and New Mexico.
Other states that have been impacted and are thousands of miles away include Hawaii, Maine, Washington and Wyoming.
Golden alga research efforts have been coordinated in different areas of the state to monitor, study and prevent large outbreaks. These include surveys, genetic studies, historic assessments and control mechanism studies.
Despite major fish kills and the loss of angling opportunities and revenues, the state is continuing its push to find out what makes golden alga tick and what it can do to protect a major Texas industry. Hopefully, the future won’t be bright for one particular menace.
For more information, visit TPWD’s golden alga resource page.