Lake Erie Algae Blooms: Scientists Identify Source of Potent Saxitoxin
ANN ARBOR, MI – december 2, 2025 – A team of researchers at the University of Michigan has made a critical breakthrough in understanding the harmful algal blooms plaguing Lake erie, pinpointing Dolichospermum cyanobacteria as the primary source of the dangerous neurotoxin saxitoxin. This discovery, published today, offers vital clues for managing and mitigating the increasingly frequent and severe blooms that threaten both wildlife and human health.
For years, Lake Erie has been susceptible to rapid cyanobacteria growth during warmer months, leading to blooms capable of releasing toxins at harmful levels. A notably concerning event occurred in 2014 when a major bloom threatened Toledo’s drinking water supply with microcystin. While scientists had previously detected saxitoxin – a potent neurotoxin considered among the most powerful naturally occurring – its biological origin remained a mystery until now.
“The main advantage of knowing which organism produces the toxin is that it helps us understand the conditions that cause toxin production – that is, what conditions make those organisms prosperous,” explained Professor Gregory Dick of the University of Michigan’s Department of earth and Environmental Sciences. “Such information can help guide policy and management, though we’re still a long way from that in this case.”
The research team, led by Paul Den Uyl, utilized “shotgun” DNA sequencing to analyze samples collected directly from the blooms. this advanced technique allowed them to reconstruct the complete genome of the organisms present and identify the genes responsible for saxitoxin production. Their analysis revealed that while several strains of Dolichospermum inhabit Lake Erie, only specific strains possess the genetic capability to produce the toxin.
Further investigation revealed a correlation between warmer water temperatures and increased levels of the saxitoxin-related gene. This finding is particularly relevant in the context of climate change and the ongoing warming of the Great Lakes. “With the warming of the lakes, one of the big questions is, how is that going to change the biological communities, including harmful cyanobacterial blooms?” Den Uyl stated.
Interestingly, the team also observed a lower prevalence of the saxitoxin gene in areas with higher ammonium levels.This suggests dolichospermum may have a unique advantage: a gene indicating its ability to utilize dinitrogen, a readily available atmospheric gas, as a nitrogen source. This capability could give the cyanobacteria a competitive edge in certain environmental conditions.
“One of the neat things about having the whole genome is you can see everything the organism can do, at least theoretically,” Dick added. “You have the whole blueprint for what the organism can do, and we do see the capability of obtaining fixed nitrogen from the atmosphere.”
This research represents a significant step forward in understanding the complex dynamics of harmful algal blooms in Lake Erie.while further study is needed to fully elucidate the factors influencing toxin production, this discovery provides a crucial foundation for developing effective strategies to protect the lake’s ecosystem and the communities that depend on it. The team plans to continue monitoring environmental conditions and analyzing the genetic makeup of Dolichospermum strains to refine predictive models and inform future management efforts.
