A team of Texas Agricultural Experiment Station fishery scientists this week took water samples from Lake Whitney for a new round of experiments. They are hoping for a breakthrough before winter when the golden algae typically blooms and kills perhaps hundreds of thousands of fish in one occurrence.
"If you have repeated blooms in the lakes, of this magnitude, eventually you'll destroy those recreational fisheries, for sure," said Dr. Daniel Roelke, Experiment Station aquatic ecology scientist, who spearheaded his team's sampling. "And not only that, (if) these blooms get into the state hatcheries, anything that is currently being raised at that hatchery, dies. This is a big problem and greater attention needs to be focused on this problem."
Roelke is collaborating with Dr. James Grover from the University of Texas at Arlington, Dr. Brian Brooks from Baylor University and Dr. Richard Kiesling from the U.S. Geological Survey as a multi-agency team seeking answers for the problem.
Golden alga, Prymnesium parvum, was first reported in inland Texas waters along the Pecos River in 1985. After the initial find, no occurrence was documented until 2001, Roelke said.
That year, algae blooms caused massive fish deaths in the Dundee State Fish Hatchery, about 20 miles west of Wichita Falls, according to Texas Parks and Wildlife Department biologists. "Bloom" is the term biologists use to describe a huge increase in the number of these one-celled plants in a given area.
Each year since 2001, the golden hues in water and the telltale dead fish in numerous Texas lakes have puzzled water and fish experts, Roelke said. So far more than 25 lakes and rivers in five of the state's major river basins have been identified as having golden alga populations, according to the parks and wildlife department.
"Typically, in our Texas systems these blooms are wintertime phenomena. They last through the winter months and into the spring," Roelke said. "But the organism can be found in the water at all times of the year, and the lab work we've done shows that the conditions are optimal for growth in the summer time not winter when the blooms occur.
"This indicates that something other than the physical and chemical environment influences the timing of the blooms," Roelke added.
Already this season, several fish kills – including a late August kill of perhaps "hundreds of thousands" of fish in the Brazos River near Possum Kingdom Reservoir – are pointing to golden alga found in water samples, according to parks and wildlife agency logs.
A large kill of fish this early in the season is unusual but points to the difficulty of finding solutions to prevent the microscopic plant from blooming, Roelke said.
One thing seems certain: Golden alga can't take a lot of salt in the water, he said. Also, the organism grows poorly in completely freshwater systems, such as lakes in East Texas where annual rainfall rates are high.
"Our lakes located in Central and West Texas, however, tend to be salty because they receive little inflow due to rainfall," Roelke said. "The lack of rainfall is what causes these systems to become a little salty (brackish), which is optimal for growth of golden algae."
But scientists also want to examine other factors that may influence lake life in various seasons, Roelke said.
"Something must happen in the spring and in the summer that prevents it from growing," he said. "Are there some kind of grazers (micro-crustaceans) out there that are present in the spring and are able to tolerate the toxins that this golden alga produces then can consume it? Or is there perhaps some kind of a virus in the water that attacks the golden alga organism?"
The team already discovered that toxicity can be removed by adding nutrients such as nitrogen, phosphorus, vitamins and trace metals. Roelke said more study is needed about golden alga life cycles because applying a treatment to massive bodies of water is not possible.
"But perhaps some form of fertilization could be developed and applied only in coves of lakes where the alga has been concentrated prior to blooming," Roelke said. "To prevent it there, might also stop its spread throughout the water system."
His lab will examine water collected in Lake Whitney through early November, then return to the same lake in February for another five-week collection period.
"The experiments under way right now focus on factors that influence bloom formation," he said, noting that once researchers understand that, "Management strategies can be formulated to prevent these factors from coming into play."
The experiments in the spring will focus on bloom termination.
Other researchers are examining environmental factors such as the role storm level wind may play in "mixing" the water and encouraging a growth spurt from the alga which otherwise had settled for a "resting period" in the depths for the season.
To see more about the statewide collaborative effort and learn how to report fish kills, see http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/ga/ .
To learn more about Roekle's research, go to http://wfsc.tamu.edu/roelkelab/
Kathleen Phillips | EurekAlert!
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