ONEKAMA — “Just because we build beautiful homes on the lake and we want to recreate on the lake doesn’t mean that it’s not a living organism we need to protect,” said Bre Grabill, environmental scientist with PLM Lake & Land Management Corp.
Grabill gave a presentation during an Onekama Township special meeting on May 25 to provide an update on what is being done to ensure Portage Lake is in good health.
Eurasian watermilfoil forms thick mats in shallow areas of a lake and can block sunlight, killing off native aquatic plants that fish and other underwater species rely on for food and shelter.
The original infestation of Eurasian watermilfoil in Portage Lake led to 40{b435bf7a99a0b4620377a2d957954f91b8ca1c72985246a997ffa130060a0e8d} milfoil coverage, according to a survey conducted in 2009.
“That’s extremely high,” Grabill said. “A level of 12 is considered very, very high. If you’re up toward 40, that’s extremely high.”
Grabill said 161 acres of Portage Lake were treated for Eurasian watermilfoil in 2009, but after a decade of management the number dropped to 49.5 acres in 2018.
• Do not rake leaves into the lake. Decomposing leaves produce more muck.
• Do not feed the ducks and geese.
• Remove dog, geese and duck droppings from lawns, docks, etc. Do not just sweep into the lake. Excess feces will increase nutrients.
• Use phosphorus-free fertilizer.
• Perforate lawn periodically, and seed and mulch exposed soil to prevent erosion.
• Remove aquatic plants, leaves, branches and other debris that washes up along the lakeshore so less decomposition occurs in or near the lake.
• Use silt fences when building a new home or doing any yard work that would cause erosion.
• Keep all burn piles and debris piles away from the lake. The ash is concentrated nutrients.
• Encourage the use of stone, brick and similar porous materials when building a landscape to minimize urban water collection.
• Create a natural buffer close to the water’s edge.
“In a lake the size of Portage Lake, milfoil is going to grow,” she said. “We’re going to have milfoil present, but what we do is survey that milfoil and determine when it’s appropriate to manage it.”
Every year, $24 million is spent to control aquatic plants in Michigan.
In 2021, less than 2.5{b435bf7a99a0b4620377a2d957954f91b8ca1c72985246a997ffa130060a0e8d} of Portage Lake required any sort of treatment, Grabill said.
Grabill said Portage Lake’s treatment program utilizes the newest form of treatment available in aquatics, with one of those products being ProcellaCOR, an herbicide with a reduced-risk rating from the U.S. Environmental Protection Agency.
“It’s really cutting-edge technology to be able to selectively remove milfoil but be able to trick the plant into responding so we don’t have herbicide resistance,” she said.
Herbicides such as ProcellaCOR are safe to use in the lake, Grabill said.
“Herbicides are designed to attack the chlorophyll of a plant, which is the green part that makes it grow,” she said. “And only plants have chlorophyll. That’s why they use herbicides to attack those plants, and why they can be used within our water bodies.”
In addition to monitoring non-native plants within Portage Lake, Grabill said algae levels must be monitored, as well.
“It’s very important that we track that because as a lake ages you’re going to see more and more productivity,” she said. “With more productivity, you’re going to see more algae. It’s an important component to determine the health of a lake based on how much algae is present.”
Starry stonewort is a macroalgae that was identified in Portage Lake in 2020. Eight acres of Portage Lake were treated for starry stonewort in 2020, and 4.5 acres were treated in 2021.
Grabill said phosphorus levels are tracked because excessive phosphorus can cause increased algae growth. She said less than 10 micrograms per liter is ideal, more than 10 is considered elevated and 30 micrograms per liter is a level “to be truly concerned about.”
Portage Lake saw levels as high as 70 micrograms per liter in 2012, but levels have been consistently below 10 in recent years.
“Back in 2012, 13 and 14, you had some very high levels of phosphorus within the water body. Those levels are high enough to show we have a true concern,” Grabill said. “However, if you look at the most recent history — except for a spike in 2017 — from 2015, 16, through current time, the phosphorus readings within the lake are considered very low, so that’s fantastic.
“… It’s important to track that so we can try to determine if there are changes taking place within the water body.”
PLM conducted a total of seven surveys on Portage Lake in 2021.
“Portage Lake has one of the most advanced and rigorous water quality testing programs that I’m aware of in the state of Michigan,” Grabill said.
Despite the extensive monitoring efforts, Grabill said it is important for area residents to keep their eyes peeled for signs of trouble within the lake.
“As much surveying as we’re doing, or the committee is having done, residents of the area are the best surveyors that I’ve found,” she said. “… You know the water body, you know the beach area, you know the lake, so you’re probably going to more quickly find something from being out there every single day. So if you notice something’s different … say something.
“It’s very important that we all act as citizen scientists to help protect the watershed together.”
There were fewer than 15 species of submerged native plants within Portage Lake when the lake management program started. The number climbed to 20 in 2021.
The lake management program has an annual budget of $83,600. In 2021, only $48,500 needed to be spent.
Onekama Township supervisor David Meister said the township is not saving the surplus funds and will instead eventually stop collecting money from the Special Assessment District — a designated area where a majority of property owners agree to allow a government agency to levy a property tax in exchange for a specific service — in order to use up the balance.
“At the end of this cycle, we want to end up with $0 in the bank account that people have paid in. The township isn’t just collecting $83,600 and pocketing $30,000,” he said. “We’ll balance all that out at the end of the cycle. There might be a year or two we don’t need to collect any money, and we will spend the money that’s in the balance.”
