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On a hot summer day, Julia Pop and��MJ Farruggia paddled a two-person pack raft to the edge of Sky Pond, an alpine lake at 11,000 feet in Rocky Mountain National Park.��

“It’s blooming!” Pop told INSTAAR fellow and assistant professor of ecology and evolutionary biology Bella Oleksy, who waited on the shore.��

To a passerby, Pop’s exclamation might have seemed odd. The lake was surrounded by granite boulders and snow. Visible vegetation was limited to a few patches of forest and sparse shrubs and wildflowers emerging from rocky crevices. But, a careful observer might have noticed a green tint to the water — which is what Pop was referring to. The lake was full of microscopic algae called diatoms.

In the past, diatoms mostly lived in the shallow waters near the shore of Sky Pond. But, in recent years, environmental changes have allowed diatoms and other algae to proliferate throughout the lake,��. It’s just one insight that has come from decades of data collection at the site.��

MJ Farruggia (left) and Bella Oleksy on the hike up to Sky Pond in Rocky Mountain National Park on June 19, 2025. (Gabe Allen)

In 2023, Oleksy’s lab took over��, which includes Sky Pond, Lake of Glass and the Loch, all in Rocky Mountain National Park. For 42 years, the program has sought to unravel how human activity, both regionally and globally, affects alpine ecosystems.

Though the program has had a long tenure, Oleksy says there are many outstanding research questions. Alpine lakes�� as a consequence of global warming. And, simultaneously, an influx of airborne chemicals from industry, agriculture and fuel combustion is changing their chemistry.

“So far, the big question is how nitrogen emissions from outside impact a remote watershed that experiences virtually no direct human impacts,” Oleksy said. “We’re also only just starting to really understand how this watershed works and all of the complicated ways it responds to both long and near-term climate patterns.”

This summer, Oleksy’s lab will return to Loch Vale once per month. The information they gather will fuel analyses to come, and contribute to one of the longest-running biogeochemical records in the Colorado alpine.��

A changing landscape

In 1983, Oleksy’s future thesis advisor,��, began a monitoring program in Loch Vale with funding from the National Acid Precipitation Assessment Program. The goal was to evaluate how acid rain, a major environmental concern at the time, was affecting alpine ecosystems.

The program's goals soon shifted when the researchers discovered that acid rain was having only a negligible effect. Instead, they observed high levels of “wet nitrogen” raining down on the watershed. At the time, the nitrogen mostly stemmed from vehicle and power plant emissions in front range cities. But, as the trend has persisted, these sources have gotten cleaner while large-scale livestock operations have become a more significant contributor.

“A lot of ammonia gets volatilized from these concentrated animal feeding operations around Greeley and elsewhere,” Oleksy said. “When we get these upslope storms in the summer, it arrives in precipitation. You can smell it on the wind all the way up here.”

Nitrogen, an essential nutrient for living organisms, is historically scarce in alpine environments. As such, its arrival en masse in Loch Vale spurred major ecological change. So far, Oleksy and collaborators have identified overall increases in several types of algae, including diatoms and filamentous green algae. They have also found that much of the nitrogen is washed downstream, where it might have further impacts.

In 2005, research at Loch Vale catalyzed a��. The effort is ongoing, and Oleksy’s monitoring efforts provide a way to assess progress.

Preventing toxic blooms

Alpine watersheds are in a period of rapid change, and the consequences of that aren’t always black and white. Using machine learning,��experiencing unseen levels of productivity. Basically, the total amount of organisms living in the lakes, largely algae, are much higher than normal.��

The ecological consequences of this change are complex, but one knock-on consequence is that these lakes may be pulling more carbon dioxide out of the atmosphere through photosynthesis. When the organisms die, that carbon is stored in lake sediment.

“These historically super clear lakes are now producing a lot more carbon,” Oleksy said. “The question is: ‘are they now more of a carbon sink than we thought?’”

When this process is pushed to the extreme, though, it can backfire. If a lake becomes too warm and nutrient-rich, it can trigger a proliferation of cyanobacteria that produce deadly toxins.��

This issue is top of mind for Oleksy’s lab. In recent years, several alpine lakes in the San Juan mountains in Southern Colorado have experienced extreme algal blooms. Pop is currently��.

“She’s looking at what species are there. Are there cyanobacteria that could produce toxins or just a lot of algae?” Oleksy explained.

The San Juans are an example of drastic and rapid environmental change. A combination of bark beetle outbreaks, wildfire and a dwindling snowpack have catalyzed a major ecological shift. For now, the Front Range has escaped environmental change at that level, but it’s not out of question as climate change progresses.��

“Compared to Northern Colorado, the climate shifts and changes to snowpack in the San Juans have been profound,” Oleksy said.��

While the San Juans might provide a window into the future, the Loch Vale monitoring program provides a window into the past. On top of 42 years of field data,��. The goal is to glean an understanding of how these ecosystems evolve over a variety of climatic and atmospheric conditions.

“I think it’s really important to have these big datasets and combine different techniques,”��Abby Ross, a PhD student in Oleksy’s lab, said. “With all of that background, we can actually tell what changes are unprecedented and need to be investigated further.”

If you have questions about this story, or would like to reach out to INSTAAR for further comment, you can contact Senior Communications Specialist Gabe Allen at��gabriel.allen@colorado.edu.

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