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Blue-green algae, or cyanobacteria, is so thick in Blue Mesa Reservoir that it turns a motor boat's wake green as a research team motors across the lake on Aug. 16, 2022. U.S. Geological Survey Hydrologist Rachel Gidley, left, and Colorado Parks and Wildlife fisheries technician Mars Charlebois, right, are part of the research team monitoring the algae bloom in the reservoir. (Dean Krakel, Special to The Colorado Sun)

GUNNISON — As Nicki Gibney steers her motorboat through the shallow waters of Blue Mesa Reservoir, she slows her boat to a stop. The deep blue water is thick with bright blue and green clumps floating on the surface. To the untrained eye, the bright colors and swirls look like a work of abstract art. 

“I tell the public to look out for what looks like pea soup or spilled paint,” Gibney says. 

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Part of Gibney’s job is to help visitors understand that these curious clumps, cyanobacteria or blue-green algae blooms, may be toxic, and could cause serious harm to humans or animals who swim in the reservoir. If the toxins cross dangerous thresholds outlined by the Colorado Department of Public Health and Environment, the park posts “no-contact closures” that advise visitors against swimming or dipping along the shores of the reservoir. 

As of late August, Gibney hadn’t had to issue warnings to the public. 

“Typically when we have had to do those no-contact closures, it’s been the first week of September,” Gibney says. “It wouldn’t surprise me either this week or next week if we maybe hit those higher levels.”

As Gibney expected, Curecanti National Recreation Area on Sept. 16 posted an alert: High levels of toxins linked to blue-green algae had been found in Blue Mesa Reservoir.  

National Park Service Aquatic Ecologist Nicki Gibney takes a water temperature reading in Blue Mesa Reservoir while monitoring the blue green algae (cyanobacteria) bloom in the lake’s water. Gibney’s team of researchers takes samples of temperature, visibility and algae bloom once a week. (Dean Krakel, Special to The Colorado Sun)

For six years, Gibney has worked as an aquatic ecologist for Curecanti National Recreation Area and Black Canyon of the Gunnison National Park, and her job is to keep an eye on the water quality in both parks. Although water scientists have sampled the waters since 2001, Gibney’s work has changed dramatically in recent years. The ongoing megadrought in the West has changed the water in Blue Mesa Reservoir: the levels are low and the temperatures are warm — creating ripe conditions for harmful algae blooms. 

With three research projects running at once, Gibney travels around Blue Mesa by boat most days of the week from April to October sampling and observing the reservoir for harmful algae blooms. The goal is to identify what is causing the large swaths of algae, and what, if anything, the park can do to prevent them.

Blue-green algae is a native species, but when it blooms, there’s trouble for everyone

Other than threatening the health and safety of visitors, algae blooms lower oxygen levels in the water creating inhabitable conditions for the fish below the surface. Their presence also limits the outdoor recreation economy that thrives during summer months. 

Toxic algae blooms are a relatively new problem for the park. Gibney and other scientists first noticed changes in the blue-green substance around the reservoir four years ago. Blue-green algae is a natural form of bacteria. A bloom is when the bacteria multiplies and groups together creating large clumps or mats. 

A thermometer taking water temperature rests in the algae infested water along the shore of Blue Mesa Reservoir. (Dean Krakel, Special to The Colorado Sun)

“In 2018 was when we really started noticing large mats forming, and the mats started changing colors, sometimes more yellowish,” Gibney says. “And it just seemed more alarming that year.”

Now, she splits her time between three projects each week, and each one is dedicated to learning more about blue-green algae. On Tuesdays, she bottles samples that she sends to the state health department to test for toxins. The results help her determine if it will be safe for visitors to swim on the weekend. 

On the other days, she works with scientists from the U.S. Geological Survey on two long-term projects that aim to learn more about blue-green algae: what species exist in the reservoir, how algae changes over the course of the summer and what makes the goopy substance turn toxic. The first is a nationwide national park project and the second is specific to Blue Mesa. Both projects will span three years and require significant funding. 

Lucca Sterrer, hydrology intern, takes samples of cyanobacteria or blue-green algae in a small arm of Blue Mesa Reservoir. (Dean Krakel, Special to The Colorado Sun)

Local organizations in and around Gunnison partnered to support the Blue Mesa project.  Collecting and testing samples for three summers will cost upward of $350,000. This includes imaging from a satellite that passes over the reservoir each week. Funders include The Upper Gunnison River Water Conservancy District, the Colorado River District, Gunnison County, the Project Seven Water Authority and the Uncompahgre Valley Water Users Association. 

Sonja Chavez, general manager of the Upper Gunnison River Water Conservancy District, helped organize funding for the project. For Chavez, supporting the project was an easy choice given the reservoir’s many uses by people who live and work in the Upper Gunnison watershed. In addition to its famous boating and fishing opportunities, it provides water storage, and the water cycles through hydroelectric dams downstream — creating power for thousands of people. 

“It’s a huge economic benefit to our community,” Chavez said. “We want to do anything we can to support that.” 

Blue Mesa Reservoir is home to over 10 different orders of algae. Blue-green algae is a bacteria that is native to the area, and is present in many bodies of water across the state and the country. And algae isn’t all bad — it is an important component of the ecosystem and is a significant food source for fish. The problem is that harmful or toxic algae blooms are on the rise and are diminishing water quality in the reservoir.

“It just seems the conditions are exacerbating how much is growing here,” Gibney says. 

Data is collected in the water and from the sky

After a 15-minute boat ride from the marina to Iola Basin, the group anchors to collect samples. Blue Mesa is less than half full and Iola is the shallowest of the three basins, with a depth of about 13 feet — about 63 feet below the reservoirs high water line. It’s also where the park has reported more frequent blooms. Though scientists are still trying to figure the cause, its likely that low water levels are making hings worse. 

“Unfortunately, it seems exacerbated when the water levels are low, and we have these really warm summers, and maybe not as many afternoon thunderstorms,” Gibney says. “And the water temperatures just get really warm.”

National Park Service hydrology tech Samantha Shelafo, right, holds up a water sample taken from Blue Mesa Reservoir so it can be photographed during the team’s weekly monitoring of blue-green algae in the lake. (Dean Krakel, Special to The Colorado Sun)

Gibney and her USGS research partner hydrologist Katie Walton-Day spend the day looking for nutrients, like phosphorus and nitrogen, to understand what is feeding and fertilizing Blue Mesa’s algae. After two summers of research, the pair admit they still have a lot to learn. 

“It’s such a new area of study that the scientific community doesn’t know which species produce certain cyanotoxins under what conditions,” Gibney says. 

Out on the water, the crew has a short window to collect and bottle samples because their work must align with a European Space Agency satellite passing overhead every five days. The satellite collects aerial images of algae blooms

Out on the water, the crew has a short window to collect and bottle samples because their work must align with a European Space Agency satellite passing overhead every five days. The satellite imagery of algae blooms is processed by the USGS Idaho Water Science Center. The goal is to combine data collected on the water with aerial images from the satellite, a method known as ground-truthing.

The pair quickly gets to work in their outdoor lab. They unpack heavy instruments, slide on rubber gloves, sanitize bottles and record their findings in notebooks and on official forms. They measure for nitrogen, phosphorous and chlorophyll. Data like temperature, depth, dissolved oxygen, conductivity and pH levels all factor into understanding what’s causing blue-green algae to turn toxic. 

They also keep an eye out for changes that are visible to the eye. The water is cloudy because of the small flecks of algae floating near the surface. Over two summers, they’ve identified three species of algae: one resembles grass clippings, the second is spherical like flecks of dandruff and the last looks like a long strand of hair. 

Walton-Day leans over the side of the boat while she carefully lowers an instrument called a Secchi disc into the water. She’s testing for clarity — when more algae is present in the water, it’s harder to see below the surface. She lowers the disc 5 feet before it’s completely out of sight, which is a significant a change from last week when the disc hit 9 feet before it disappeared. 

After a few hours, they pack up their gear to grab another sample in Cebolla Basin. Gibney and Walton-Day note that while blue-green algae is present, it’s less noticeable in this basin, which is much deeper — 100 feet. After collecting and bottling a few samples, the group heads back to the official lab, on land, and prepares the samples for transport to USGS labs in Denver for testing. 

Samples of Blue Mesa Reservoir water wait to be shipped to a lab in Denver after being gathered during a research teams weekly monitoring of the cyanobacteria bloom. (Dean Krakel, Special to The Colorado Sun)

Walton-Day says the million-dollar question in the field of studying harmful or toxic algae blooms is figuring out the trigger, or the cause. 

“We’ll be lucky to find a trigger, and we’re looking more for patterns,” Walton-Day says. “The trigger is like the magic bullet everyone wants to figure out.” 

But she says so far, they are certain a handful of factors are working together. 

Drought has created lower water levels and higher water temperatures — ripe conditions for algae to grow. The surrounding geology, like phosphorous-rich soils and rocks, erodes into the reservoir and feeds algae. Discharges upstream, like agricultural runoff and discharge form the local wastewater treatment plant, might play a role in the reservoir’s changing waters. 

Harmful or toxic algae blooms in Colorado are not unique to Blue Mesa Reservoir. Scientists have recorded blooms in lakes in Rocky Mountain National Park, and bodies of water on the Front Range, like Bear Creek Lake Park, announced closures this summer. 

Gibney says one of the hardest parts of her job is communicating safety messages to the public. The samples she collects on Tuesday are sent to a lab that day, and she receives the results on Friday — just in time to inform visitors before the weekend. Gibney says conditions change so quickly that it’s hard to know if the information is 100% up to date. 

“That’s tricky because the turnaround time is really hard,” Gibney says. “We get the results for the weekend, and we’re seeing things change within the five-day period.” 

Symptoms from contact with the water might include a skin rash, nausea, vomiting or dizziness. Animals and children are at greater risk because of their small body mass. To date, the park hasn’t confirmed any cases of illness that trace back to visitors swimming in the water. 

With almost two years of data in the books, Gibney hopes the third year will add more information to the already robust study. Then, she hopes the park can make a plan to address the algae blooms before they begin. 

“The long-term goal for the park once we learn about the timing and understand the nature of the blooms, is to figure out what we can do to help stop them,” Gibney says.

Blue-green algae or cyanobacteria, is so thick in Blue Mesa Reservoir that it turns a motor boat’s wake green as a research team motors across the lake. Researchers have identified three species, including one that looks like strands of hair. (Dean Krakel, Special to The Colorado Sun)

Special to The Colorado Sun Twitter: @SMaltarich