A large algae bloom that could harm fish populations is occurring along the Gallatin River and sections of the West and Taylor forks, according to Montana officials.
The bloom is widespread, stretching 22 miles along the Gallatin River and on additional parts of the West Fork and Taylor Fork, according to Kristin Gardner, executive director of the Gallatin River Task.
The task force has been monitoring water quality in and around the river for almost two decades, collecting data to track nutrient levels, streamflow and aquatic insects.
Darrin Kron, a water monitoring specialist with the Montana Department of Environmental Quality, said the DEQ has been coordinating with the task force. He said algae that grows along the Gallatin is a non-toxic, filamentous variety called cladophora.
The non-toxic blooms have the potential to harm juvenile fish and sculpin populations, and can cause shifts in the kinds and quantity of bugs around the river, said Chace Bell, another DEQ water monitoring specialist.
If the blooms become regular, mayflies and caddisflies could become less common, and scud species could become more prevalent, he said.
The task force and the DEQ first detected an “algae problem” in the West Fork in 2005, and blooms since then have regularly shown up during summer months. Kron said this year, the DEQ received reports about algae growing heavily in the Gallatin beginning in early August.
The agency, along with the task force, have since collected samples to monitor the bloom. Lab results still haven’t come in, according to Kron.
Hard water, elevated levels of nitrates and phosphorus, higher water temperatures and sunny weather all drive algae growth, Bell said. Long, sunny days allow the algae to photosynthesize and spread quickly. The algae depletes the water’s oxygen, harming other organisms.
While some factors that contribute to the blooms can’t be controlled, Gardner said people can take steps to reduce the amount of nutrients that enter the waterway. Fertilizer used on lawns, older septic systems and phosphorus released during stormwater construction all contribute to nutrient loading.
Guy Alsentzer, executive director of Upper Missouri Waterkeeper, a nonprofit that defends clean water, said it doesn’t take much for nutrient levels to reach a tipping point, and algae blooms are the “canary in the coal mine.”
“Too many nutrients are coming from manmade sources,” he said. “Right now, a lot more work needs to be done to control pollution.”
To limit nutrient loading, “Big Sky needs a centralized wastewater treatment system,” he said.
The town recently approved funding for an upgraded water and sewer district.
Alsentzer said the people of Big Sky and others living along the river should also use smart growth technology, plan development conscientiously and pay attention to what is going into the groundwater.
“It’s time for us to say, ‘Where is this coming from?’” Alsentzer said. “We need to grow responsibly to protect the golden goose.”
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