McGill Researchers Uncover Bacteria as Early Warning for Algal Toxins

Researchers at McGill University have discovered a type of bacteria capable of indicating the potential toxicity of blue-green algae, also known as cyanobacteria. This breakthrough offers a promising early warning system for assessing water safety, especially as cyanobacterial blooms are becoming more frequent due to climate change.

The study, spearheaded by Lara Jansen in the lab of Professor Jesse Shapiro, highlights that shifts in bacterioplankton populations correlate with the broader bacterial community during these toxic blooms. Conducted while Jansen was a PhD student on exchange from Portland State University, the research has significant implications for public health and environmental monitoring.

Link Between Bacteria and Cyanotoxins

Cyanobacterial blooms can produce harmful contaminants known as cyanotoxins, which pose risks to human health, pets, and wildlife. Jansen’s team analyzed water samples and extracted DNA from the aquatic bacterial community, or bacterioplankton. They compared this data against a comprehensive database of DNA sequences to identify specific bacteria present in the lakes studied.

Jansen emphasized the cost-effectiveness of this method, noting, “Sampling bacteria is a relatively cost-effective measure, because DNA sequencing costs have come down a lot.” This is particularly useful for monitoring sites far from urban centers, where resources may be limited.

The team also tested for microcystin, the most prevalent cyanotoxin in such environments, and found a correlation between its presence and the identified bacteria. Their findings suggest that a rise in certain bacterioplankton could signal the need for further testing of water safety.

Consistent Findings Across Diverse Ecosystems

Unlike previous studies that focused on similar lakes, this research compared two ecologically distinct lakes in the Cascade Mountains, each with varying nutrient levels. The results revealed that the shifts in bacterial communities can effectively reflect bloom toxicity across different ecosystems.

“These mountain lakes are popular for recreation and exist at the headwaters of major drinking water sources,” Jansen explained. “Cyanotoxins don’t always degrade quickly, so there’s potential for downstream migration.” The researchers argue that current toxin testing methods are costly and must be repeated throughout bloom periods, making Jansen’s findings a more efficient alternative.

The implications for public health communication are significant. Despite existing advisories regarding harmful algal blooms, Jansen observed that recreational activities continue, which can lead to exposure. “I had to encourage people myself not to go in the water,” she remarked. Limited personnel often hinder agencies’ ability to effectively communicate risks.

This research aims to improve understanding of how bacterial populations respond to toxic blooms, ultimately guiding public health interventions.

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. This work not only advances scientific knowledge but also enhances the potential for safeguarding public health in the face of environmental challenges.