Tanya Bachman’s birthday celebration on the Columbia River near Portland, Oregon, took a tragic turn in August 2024 when her border collie, Jax, succumbed to a rapidly fatal poisoning. What began as a cherished family tradition, boating with their two dogs on the river, ended in heartbreak when Jax, after a brief period of illness, died less than an hour after his owner noticed his tail drooping. The veterinarian’s diagnosis pointed to a likely ingestion of toxic cyanobacteria, a type of algae that forms blooms. Jax’s death highlights a growing, and often unseen, danger lurking in the West’s waterways: benthic cyanobacterial blooms.

These blooms, often described as resembling globs of snot, form on the bottoms of streams or on submerged objects like logs and rocks. Unlike the more familiar planktonic blooms that float on the surface of lakes and reservoirs, appearing like grass clippings or spilled paint, benthic blooms can be more insidious, sometimes detaching and rising to the surface. Scientists have been documenting these benthic blooms with increasing frequency in the Western United States for approximately the past five years.

Cyanobacteria, the microorganisms responsible for both types of blooms, have been a part of Earth’s aquatic ecosystems for billions of years. However, their proliferation is significantly amplified by human activities and environmental changes. Excess nitrogen and phosphorus, primarily originating from agricultural fertilizers and air pollution, act as potent nutrient sources that fuel rapid algal growth. Compounding this issue, climate change is creating conditions conducive to more frequent and widespread blooms. As water temperatures rise, particularly during hot, dry years, water bodies become warmer and more stagnant, creating ideal breeding grounds for cyanobacteria. Hannah Bonner, a professor and water scientist at Brigham Young University specializing in benthic cyanobacteria, notes that climate change is a significant contributing factor to this concerning trend. This presents a grim paradox: as the Western landscape warms, once-valued cool-water havens are transforming into potential threats, endangering not only pets but also human health and wildlife.

The toxins produced by cyanobacteria in both benthic and planktonic blooms can have severe consequences. Direct contact with the water can cause skin irritation in humans. Ingestion, whether through drinking contaminated water or licking contaminated fur, can lead to gastrointestinal distress, nausea, and even severe liver damage. For pets, livestock, and wildlife, the effects can be swift and fatal. Alarmingly, standard backpacking water filtration systems are incapable of removing these potent cyanobacterial toxins, leaving recreationalists and their animals vulnerable.

While the dangers of cyanobacteria have been recognized for some time, the monitoring and tracking of these blooms have historically lagged, particularly for the less visible benthic forms. Most Western states began to formally track planktonic blooms, which are more readily observable, primarily in response to significant public health events in the Eastern United States. A pivotal moment occurred in 2014 when toxic cyanobacteria blooms in Lake Erie led to the shutdown of Toledo, Ohio’s municipal drinking water system, raising widespread awareness of the potential risks. This event spurred many Western states to implement or enhance their monitoring programs. Wyoming initiated bloom monitoring in 2018, initially using satellite imagery and later incorporating on-the-ground water sampling in 2021. Utah increased its monitoring efforts in 2016, recognizing the growing prevalence of harmful algal blooms across its water bodies. California and Oregon have some of the longest-standing monitoring programs in the West, with initiatives dating back approximately two decades.

Data emerging from these and other monitoring programs indicate a clear trend: planktonic blooms are appearing earlier in the spring, are present in a greater number of lakes and reservoirs, and are persisting later into the fall season. While some experts suggest that increased reporting may partly account for these observed increases, a comprehensive 2021 study by the Environmental Protection Agency provides strong evidence that the synergistic effects of increased nutrient loads (nitrogen and phosphorus) and the warming and drying impacts of climate change are indeed creating more numerous and longer-lasting blooms nationwide.

Theodore Dreher, a professor emeritus of microbiology at Oregon State University, emphasizes that human activities on the land surface are significantly contributing to these issues. "We’re affecting so much of the land surface and creating disturbances and introducing nutrients," he stated. Unlike climate change, where emissions from one region can impact global weather patterns, nutrient pollution often has more localized sources that can be more effectively managed through targeted regulations. Utah, for instance, has taken proactive steps by implementing regulations to improve wastewater treatment facilities and offering voluntary incentives for practices that reduce agricultural runoff and restore natural floodplains. These combined efforts have shown success in mitigating nutrient flows into Utah Lake near Provo, a body of water that was once so plagued by blooms that locals humorously marketed merchandise with the slogan "Ski the Scum."

However, a more robust approach is needed to effectively address the root causes of these blooms. Justin Hayes, Northern Rockies conservation director with American Rivers, argues that simply warning the public about existing blooms is insufficient; states must prioritize collecting comprehensive water quality data to understand and tackle the underlying issues. "States need to take this really seriously and start trying to solve it rather than just warning people," Hayes urged.

Researchers are also grappling with understanding the emergence of blooms in unexpected locations. Planktonic blooms are increasingly being observed in high-elevation lakes, seemingly remote from typical pollution sources like septic systems and livestock operations. Scientists hypothesize that runoff from melting glaciers or the atmospheric deposition of nitrogen and phosphorus from dust and air pollution may be contributing to these occurrences, as suggested by Bonner. Furthermore, the decline in snowpack and subsequent reduction in snowmelt could lead to an increase in benthic blooms. Simultaneously, some regions are experiencing fewer monsoon rainstorms, which previously helped to clear away algal mats. "I was just in the mountains last weekend, in a pristine creek, and they were everywhere," Bonner reported, underscoring the pervasive nature of the problem.

While Bonner advises against complete avoidance of outdoor recreation, she stresses the importance of recognizing the signs of potential danger. She describes benthic blooms as resembling "a big ball of snot" and offers a practical tip for identification: if a substance found in the water, when poked with a stick, reveals hairlike strands or fibers, it is likely not cyanobacteria and therefore not toxic. However, if it has a "boogery consistency," it is a strong indicator of the presence of toxic cyanobacteria.

In response to these growing concerns, more states are implementing public awareness campaigns, including the installation of warning signs, distribution of email alerts, and issuance of public health advisories to inform recreational users about the presence of toxic blooms. Tanya Bachman continues to share her story with local and regional media outlets, hoping that the tragic loss of Jax will serve as a stark warning and prevent other pet owners from experiencing similar heartbreak. "Everything upstream flows downstream," Bachman emphasized, a poignant reminder that the health of waterways is interconnected, and a problem originating in one location can inevitably impact others downstream.

Reporting for this story was supported by the Mighty Arrow Family Foundation.