Though phosphorus has long been referenced as one factor that causes the harmful algal blooms on Utah Lake, researchers at Brigham Young University have found a link between the levels of the nutrient in the lake and the algal blooms the lake has become infamous for in recent years.
Over a two-year period, the research team measured phosphorus concentrations in lake sediment, pore water and the water column.
After this initial study was complete, the research found that the phosphorus concentrations are higher on the east side of Utah Lake, which is where treated wastewater from Utah County cities is discharged into the lake. Wastewater isn’t treated for phosphorus, meaning the discharge puts higher concentrations of phosphorus into the lake, according to Greg Carling, a BYU geology professor and co-author of the published paper on the research.
“I would say this was the first study to quantitatively look at phosphorus chemistry across the lake,” Carling said. “People have been talking about it, but nobody has actually gone in and measured phosphorus in sediment and pore water across the lake.”
The phosphorus basically acts like a fertilizer for the cyanobacteria, which is what produces the toxins that frequently shut down portions of the lake. While these blooms occur all over the lake, they occur more commonly on the east side where levels of phosphorus are higher.
“What we found from that study is there likely is a link between legacy phosphorus that had accumulated over decades and the location of harmful blooms,” Carling said.
While the study doesn’t prove that phosphorus is the only factor related to harmful blooms on the lake, Carling said it does confirm that phosphorus is related to harmful algal blooms.
One surprising part of the study, Carling said, was that they found much of the phosphorus in the sediment was “mobile” meaning it could easily transfer to the water column.
Because of the levels of phosphorus in the system, though, Carling said even if wastewater plants started treating for phosphorus immediately, it would likely take years before you would see a drop in phosphorus levels in Utah Lake.
“Even if you immediately start to clean up the water column, it’s possible that we still get phosphorus coming up from the sediments, and that could take years or decades to be completely removed,” Carling said. “So it’s not like something we could just put in hundreds of millions of dollars, clean up the treatment plants and see an immediate improvement. It’s going to be something of a longer process.”
Exactly how long it would take is unknown, though it is a question that’s being asked by experts on a state-level science panel Carling sits on. Studies on other lakes show it could take anywhere from 10 to 30 years.
“That’s the whole point of the science panel,” Carling said. “They want to know what’s the target amount of phosphorus we can put in the lake to achieve better water quality?”
Even with a target goal for phosphorus achieved, it’s still likely there would continue to be algal blooms on Utah Lake.
Many factors go into the blooms, such as water temperature, weather and nutrients. There are people who argue that there is enough naturally-occurring phosphorus in the lake that there will still be algal blooms even if no human-contributed phosphorus is put in the lake. Other factors like increased temperatures due to global warming could also exacerbate algal blooms regardless of phosphorus levels, Carling said.
“There are lots of things that go into creating harmful algal blooms, Carling said. “Nutrients are just one thing that can readily be controlled.”
But, Carling said, no matter what is done to restore Utah Lake, it will never be a clear, blue lake like Lake Tahoe.
There is ongoing research at BYU to see what historic levels of phosphorus in the lake were, Carling said, by gathering a sediment core. Finding that type of historical information about the lake is one of the most important parts of understanding how to restore Utah Lake to its optimal condition, Carling said.
While it won’t happen overnight, Carling said he’s optimistic about the possibility of improving the lake.
“I think we can come up with solutions that will improve the lake,” Carling said. “...It’s a resilient lake. It’s pretty good at processing the nutrients we put into it and cleaning itself up. I think if we’re willing to do simple things, like remove some of the input, the lake will take care of itself. I don’t think we need anything too extreme like dredging the lake.”