Researchers at BYU examined the sediment content of Utah Lake and its connection to toxic cyanobacteria
Utah Lake is one of the largest freshwater lakes in the United States. Each summer, the body of water is used by thousands in the Utah Valley as a place of recreation to go boating and fishing.
However, due to unique circumstances, the lake has occasionally been shut down to protect people from dangerous toxins in the water, which come from what is commonly referred to as “algal blooms.” Recently, by examining the sediment in the lake, researchers at BYU looked at the causes of the cyanobacteria blooms and at new ways to possibly clean up the lake.
“Phosphorus is a nutrient that drives the algal blooms; it's a fertilizer,” said BYU geology professor and co-author of the paper Greg Carling. “There's a close connection with what's happening in the sediments and what's happening in the water column, so the nutrients like phosphorus that are stored in the sediments can easily be released and affect the overlying lake water.”
According to Carling, cyanobacteria, the bacteria that produces the harmful toxins, looks like algae: both manifest in greenish mats so it’s commonly referred to algal blooms. For the study, the researchers gathered measurements of cyanobacteria counts and were able to correlate that to areas where there’s higher phosphorus concentrations in the sediment.
“A lot of the phosphorus we see in the lake comes from the wastewater treatment plans,” Carling said. “Over decades, the phosphorus has accumulated in the sediments. Currently, there are treatment plants all along the east side of the lake which is one of the factors contributing to these blooms and the reason we see the higher concentrations in that area.”
To identify the potential influence of phosphorus on cyanobacteria, the team evaluated the abundance of total cyanobacteria and three dominant cyanobacteria species in relation to phosphorus concentration across the lake.
“Utah Lake has all the right ingredients to produce algae and cyanobacteria,” Carling said. “There are a variety of factors that contribute to creating the right environment for the algae and cyanobacteria to grow. For example, the lake is shallow which causes the water to heat up more quickly than a deeper lake and the sediments to get stirred up more easily by wind.”
Over a two-year span, the group measured phosphorus concentrations in three lake compartments: the sediment, pore water and water column. A total of 26 samples of all three compartments were collected from 15 sites across Utah Lake.
The study, which was published in PLOS One, a top-ranked science journal, suggests limiting the amount of nutrients coming out of the treatment plants would likely help but acknowledges it would take a long period of time to see a big change because of phosphorus stores in lake sediments. A stepwise approach for decreasing external nutrient inputs, while balancing costs of water treatment, is the best way to improve water quality.
The other authors of the study include BYU professors Zach Aanderud, Kevin Rey, Neil Hansen, Barry Bickmore, Stephen Nelson and BYU students Matthew Randall and Dylan Dastrup, as well as Theron Miller from the Wasatch Front Water Quality Council.