McGill Researchers Uncover Bacteria for Early Blue-Green Algae Warnings

Researchers at McGill University have identified specific bacteria capable of indicating the potential toxicity of blue-green algae (cyanobacteria) blooms. This discovery could serve as an early warning system for water safety, particularly as blooms become increasingly frequent due to climate change.

Cyanobacteria can produce a range of hazardous contaminants, known as cyanotoxins, which pose serious health risks to humans, pets, and wildlife. The study, led by PhD student Lara Jansen in the lab of Professor Jesse Shapiro, highlights how shifts in bacterioplankton populations correlate with the overall bacterial community during these blooms.

Jansen, who conducted this research while on exchange from Portland State University, discovered that certain bacterioplankton were more prevalent in toxic blooms. This suggests their abundance could be a reliable indicator for further testing, prompting necessary evaluations of water safety in affected lakes.

Cost-Effective Monitoring Technique

The research team collected water samples and analyzed DNA extracted from the aquatic bacterial community, known as bacterioplankton. They compared these samples against a comprehensive database of DNA sequences to identify the bacterial types present. Jansen noted, “Sampling bacteria is a relatively cost-effective measure, because DNA sequencing costs have come down a lot.” This method is particularly valuable for remote locations often lacking access to major urban centers.

Additionally, the researchers tested for microcystin, the most common cyanotoxin found in these ecosystems, and established a temporal relationship between the presence of these bacteria and cyanotoxin levels. This finding supports the idea that shifts in bacterial populations may serve as early indicators of potential toxicity.

Broad Implications for Ecosystems

Unlike previous studies that focused on similar lakes, this research compared two ecologically distinct lakes in the Cascade Mountains, which varied in nutrient levels. The results indicated that bacterial communities reflect bloom toxicity across diverse ecosystems. Jansen explained, “These mountain lakes are popular for recreation and exist at the headwaters of major drinking water sources.” Since cyanotoxins can persist and migrate downstream, the implications for public health are significant.

Current methods for testing toxins are often costly and require repeat evaluations throughout bloom periods. Jansen’s approach offers a more efficient alternative, potentially reducing the need for frequent testing and indicating when further analysis is warranted.

Enhancing Public Safety Communication

Despite these advancements, Jansen acknowledged the ongoing challenge of effectively communicating risks associated with harmful algal blooms. “There can be advisories in place, but people are still boating – and water aerosolization can carry toxins into the air,” she stated. Public health agencies strive to manage these risks, but limited personnel can complicate communication efforts.

Understanding the response of bacteria to toxic blooms could enhance risk communication strategies, leading to more timely public health interventions. This research serves as a critical step towards improving water safety and protecting communities from the dangers posed by cyanobacteria.

The study titled “Shifts in bacterioplankton during cyanobacterial blooms reflect bloom toxicity and lake trophic state” was published in the journal Harmful Algae in November 2025.