The slimy brownish-green mats clinging to rocks in Virginia's Shenandoah River are telling a story that Rosalina Stancheva Christova has been learning to read for more than 20 years. As an assistant professor at George Mason University's Algal Ecology Lab, Christova has devoted her career to understanding Microcoleus, a mat-forming cyanobacterium found in waterways worldwide—and the puzzle it presents: some strains threaten human and animal health, while others pose no danger at all.
Now, working in her own backyard, Christova and her colleague A. Bruce Cahoon from the University of Virginia's College at Wise have made a discovery that rewrites part of that story. With support from a 4-VA collaborative research grant, the team spent two years collecting benthic mats from 11 sites across the North and South Forks of the Shenandoah River. What they found was both remarkable and unexpected: among the samples they identified six cyanobacteria species—and not all of them were what they seemed.
Some of the organisms the team collected weren't Microcoleus at all. Instead, they uncovered a newly discovered genus called Limnofasciculus, which was first identified just in 2023. The revelation came through careful phylogenomic analysis, with 16S rRNA gene sequencing confirming the identity of each strain. The team also isolated two distinct Microcoleus strains from the river: one nontoxic and one that produces anatoxin-a, a dangerous neurotoxin. "Phylogenetic analyses confirmed that both strains belong to the genus Microcoleus. The toxic strain was most closely related to M. anatoxicus from California, confirming the wide distribution of this problematic cyanobacterium," Christova explained.
The success of this project reflects the collaborative spirit of modern scientific research. Christova worked alongside co-investigator Benoit Van Aken, an associate professor in the Department of Chemistry and Biochemistry, and Pat Gillevet, director of the Microbiome Analysis Center. Graduate students Jacob Mormando, Sydney Brown, and Rwan Alsaadi contributed essential fieldwork and lab analysis, while undergraduate researchers—including biology major Armon Ghaffari and environmental science major Emma Boyden—supported molecular studies and data analysis. The team also drew on expertise from colleagues at the University of New Brunswick in Canada and the Interstate Commission on the Potomac River Basin, whose staff had been investigating harmful algal blooms in the river independently.
The findings carry real significance for the Shenandoah River ecosystem and beyond. Understanding which cyanobacteria species are present, where they flourish, and whether they produce toxins is essential for protecting water quality and public health. The team has already begun sharing their work with the scientific community, presenting findings at the Society for Freshwater Science Annual Meeting, the Southeastern Phycological Colloquy, the Potomac River Conference, and most recently at the 2025 Biennial Coastal and Estuarine Research Federation Meeting in Richmond. As harmful algal blooms pose an increasing threat to freshwater and coastal ecosystems worldwide, research like this—grounded in careful observation and rigorous science—offers a foundation for better protection of the rivers and lakes we depend on.