Cause not yet determined
By Sarah Gianelli EBS Senior Editor
BIG SKY – In late July, the nonprofit Upper Missouri Waterkeeper began investigating a significant bright green algae bloom in the Gallatin River from the West Fork confluence to Moose Creek, and in the valley from Axtell Bridge south of Belgrade, to Williams Bridge in Three Forks, where the Gallatin meets the Jefferson River.
Around that same time, Gallatin River Task Force began receiving numerous reports of a severe algae bloom on various tributaries of the Gallatin River. On Aug. 3, Montana Department of Environmental Quality confirmed that the discoloration is due to a proliferation of a type of algae.
Michael Suplee, Ph.D., of the Water Quality Standards & Modeling Section of Montana DEQ, released a statement that the filamentous algae “is not a cyanobacterial species (i.e., the ones that form harmful algal bloom in lake and reservoirs). Coloration of these types of attached river algae vary in accordance with nutrient availability, light, temperature, etc.; for example, I have observed that Cladophora spp. are light-green in the absence of available nitrogen and phosphorus, and deep emerald green when nutrients are abundant.
“I do not have an immediate response as to what the drivers may be that are causing this particular algae to proliferate in the river,” he continued. “DEQ is, as you are surely aware, carefully investigating similar attached algae growths on the Smith River.”
On Aug. 15, in response to an inquiry about further findings, Kristi Ponozzo, Montana DEQ public policy director, wrote in an email to EBS that “our folks here at DEQ have not been to the river and don’t have any updates on this.”
The Gallatin River Task Force receives funding from Montana DEQ to regularly monitor nutrients and algae biomass and has plans to sample 21 sites for algae and nutrients this month using DEQ protocols. The sites include seven on the mainstem of the Gallatin, 11 in the West Fork watershed, and three in the Taylor Fork.
“These analyses are time consuming,” Gallatin River Task Force education and communications coordinator Stephanie Lynn explained. “And we don’t expect to have results until the fall. At that time, we will know more.”
In the meantime, Upper Missouri River Waterkeeper Executive Director Guy Alsentzer said that the
the bloom in the mainstem Gallatin has remained consistent in terms of scope and significance, covering at least 75 percent of river bottom in most flatwater stretches and pools for about 7 miles downstream of the West Fork confluence.
Alsentzer wrote in an email to EBS, “While assessing the extent and significance of the Gallatin’s summer algal bloom is indeed technical and time and resource intensive, the river deserves nothing less than a hard look at this pollution event, science-based estimates of causes and sources of pollution, and an unrelenting determination at finding meaningful solutions that protect this important waterway and the communities and businesses it supports.”