Algae blooms, fueled by excess nutrients in the environment, have become a frequent summer occurrence in local lakes, potentially creating unsafe conditions for swimmers and other water users. At Lake Iroquois, a team of researchers from the University of Vermont is studying how one of these nutrients – phosphorus – gets into the lake, and their investigation could one day aid in control and mitigation efforts.
Algae blooms can introduce toxins into the water that can be dangerous to people and pets, according to the Vermont Department of Health website. “High phosphorus concentrations are believed to be a primary source of nutrients that have contributed to very significant growth of algae and plant species, which are detrimental to utilization of the Lake Iroquois for recreational activities,” said UVM Civil and Environmental Engineering graduate student Matthew Trueheart.
He added that both the lake’s location relatively near campus and cooperation from nearby residents help to make the research here possible.
“We are excited they are doing this work in Lake Iroquois,” said Lake Iroquois Association secretary Jamie Caroll, noting that the researchers met with LIA officers regarding the study. “More information about the lake will enable LIA and others to focus limited resources in the areas that will show the greatest benefit to the ecosystem.”
The researchers’ goal is to find out if groundwater is an important source of phosphorus in Lake Iroquois, Trueheart explained, as part of a larger effort to find ways to limit phosphorus making its way into the lake.
Trueheart, working with a team including UVM Civil and Environmental Engineering Professor George Pinder and undergraduate student Sam Marano, has been making trips out into the water from Lake Iroquois’s boat launch this summer. They are gathering groundwater samples from several places on the lake’s bottom to determine their phosphorus content, and collecting groundwater flow rate data at multiple locations.
Putting the flow data together with the phosphorus measurements will allow the researchers to figure out the rate at which phosphorus is getting into the lake, Trueheart explained.
Studying how groundwater-derived phosphorus reaches the lake is important, Trueheart noted, because although groundwater can be a substantial source of phosphorus, its journey into the lake can be complex and difficult to trace, making excess phosphorus difficult to manage; sometimes phosphorus makes its way to the lake from far away or over the span of decades.
“This lag time can complicate remediation efforts,” Trueheart said, and sometimes, even after restoration work has occurred, phosphorus will continue to enter the lake for years. Making sense of phosphorus’s winding path to the lake may help researchers determine how to halt its entry.
LIA newsletters from 2015 and 2016 discuss ongoing algae monitoring efforts at the lake, and “lay monitors” track nutrient levels, according to the LIA website; educational resources on the site discuss the dangers of “phosphorus enrichment,” reflecting the importance of monitoring and controlling phosphorus and other nutrients in Lake Iroquois.
The project also has larger implications, noted Trueheart. “We would like to apply what we learn about measuring phosphorus input through groundwater from this project to areas of the Lake Champlain basin that are hard-hit by algae blooms,” he said. “These blooms are fueled by excess phosphorus, so it is important to know how much of this phosphorus is coming from groundwater versus other sources.” The study’s results may then yield insight into research at other lakes, too, Trueheart said.
“We look forward to hearing their results from the seepage meters, to further learn about nutrient flows into the lake,” Carroll said. “It’s exciting that they are using Lake Iroquois to test this technique that [may be] expanded to help further understand the larger Lake Champlain watershed and ecosystem.”