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UM researchers investigate human impact on backcountry lakes

by UM News Service
| October 6, 2021 9:00 AM

FLATHEAD LAKE – After another summer of record-breaking tourism, it remains clear that Montana’s natural environment and breathtaking backcountry continue to draw numerous visitors who serve as a major economic driver for the state. This increase in tourism recently led University of Montana graduate student Daniel Pendergraph to pose the question: What impact might this boom in human activity have on the pristine water quality of backcountry lakes?

In a new study published in Wilderness & Environmental Medicine, Pendergraph – lead author and now a graduate of the W.A. Franke College of Forestry and Conservation’s Wilderness Institute – joined a team of UM Flathead Lake Biological Station researchers and others to determine if increased human visitation to the Absaroka-Beartooth Wilderness Area led to an increase in human fecal contamination in backcountry lakes.

Combining a traditional fecal bacterial assay with a more novel genetic approach using polymerase chain reaction analysis, researchers found that while fecal contamination was present in some bodies of water, in most cases the source of that contamination did not appear to be human.

With hundreds of lakes and over 1100 km (684 miles) of trails, the Absaroka-Beartooth Wilderness Area in south-central Montana is extremely popular among outdoor recreationalists, including those interested in backcountry backpacking and horseback travel. Visitors to the area often concentrate their activity around lakes and water sources near popular summits.

“Although the region is remote,” Pendergraph said, “increasing human visitation to the Absaroka-Beartooth Wilderness Area has the potential to negatively affect water quality, with particular concern about human-derived fecal contamination.”

Examining water samples that were collected from 21 remote alpine lake outlets and two snowmelt streams in the area, Pendergraph and FLBS Freshwater Research Lab Manager Adam Baumann used standard fecal bacterial assays to search for total coliform bacteria, as well as concentrations of Escherichia coli (E. coli) – a common bacteria found in all fecal matter. These are the same tests UM’s bio station uses to help monitor the water quality of public swimming areas in Flathead Lake through the citizen science-led Swim Guide Project.

At the end of the analysis, the researchers determined that E. coli was present in 52% of the sampled sites. From there, Pendergraph worked with FLBS Professor of Microbial Ecology Matthew Church and Research Associate John Ranieri using digital droplet PCR assays to amplify and search for specific genes known to occur in bacteria associated with human waste. Human-associated bacteria were found in very low abundances in all sites tested, which means they were present but not quantifiable. Only one of the sites had a quantifiable presence of human-associated bacteria, but the number was still relatively low.

“Our research suggests that the major sources of total coliform and E. coli in the Absaroka-Beartooth Wilderness Area could derive from wild animals in addition to livestock, pack animals or pets brought in by human visitors,” said Pendergraph.

For researchers, the results of the study were highly encouraging. To this point, it seems the increase in recreation in the Absaroka-Beartooth Wilderness Area has not yet led to a decrease in backcountry water quality as a result of human waste. But the positive implications of the study don’t end there.

“These results highlight the utility of combining more traditional assays with emerging microbial source tracking with DNA- and PCR-based methods,” Church said. “We suspect there will be an increasing number of studies that will benefit from this approach.”

It’s important to remember that, while the human impact was minimal, the study did reveal a widespread presence of total coliforms and E. coli in backcountry water sources. Researchers stress the importance of purifying water collected in any backcountry area before consumption.

Equally important is the continued practice of safe and responsible recreation to ensure the ecological and economic sustainability of Montana’s natural resources for generations to come.

For the complete study, visit Wilderness & Environmental Medicine. Other researchers in the study included Alexander Metcalf and Thomas Deluca in UM’s College of Forestry and Conservation and Lochlin Ermatinger of the Montana State University’s Department of Land Resources