GMU Researchers Identify Toxic Cyanobacteria In Shenandoah River Study

VIENNA, VA — A team of researchers led by George Mason University has uncovered new insights into potentially harmful cyanobacteria living in the Shenandoah River, including the identification of a toxin-producing strain that could pose risks to people, animals and aquatic ecosystems.

Rosalina Stancheva Christova, an assistant professor in George Mason University's College of Science, has spent more than 2 decades studying Microcoleus, a mat-forming cyanobacterium commonly found in streams and lakes around the world, according to a GMU press release. While some strains are harmless, others can produce toxins that threaten environmental and public health.

Seeking to better understand the organism's presence in the Shenandoah River, Christova partnered with University of Virginia-Wise researcher A. Bruce Cahoon on a project examining the diversity, distribution and toxicity of cyanobacterial mats in the river system.

The collaborative effort received funding through a 4-VA research grant titled "Integrative Characterization of the Anatoxin-a-Producing Benthic Cyanobacterial Genus Microcoleus in the Shenandoah River."

Over a 2-year period, researchers collected benthic mats from 11 sites along the North and South forks of the Shenandoah River. The findings yielded several surprises, including evidence that some samples previously believed to be Microcoleus actually belonged to Limnofasciculus, a newly identified genus first described in 2023.

In total, the team identified 6 cyanobacterial species and isolated two monoclonal Microcoleus strains — 1 non-toxic and another capable of producing anatoxin-a, a powerful neurotoxin.

"Phylogenetic analyses based on 16S rRNA gene sequences confirmed that both strains belong to the genus Microcoleus," Christova said in a statement. "The toxic strain was most closely related to M. anatoxicus from California, confirming the wide distribution of this problematic cyanobacterium."

The project involved a broad team of faculty, graduate students, undergraduate researchers and outside collaborators. George Mason researchers Benoit Van Aken and Pat Gillevet served as key collaborators, while graduate students Jacob Mormando, Sydney Brown and Rwan Alsaadi contributed fieldwork, laboratory analysis and ecological studies.

Undergraduate students from George Mason and UVA Wise also assisted with data analysis, laboratory maintenance and molecular research.

The study also benefited from collaboration with Gordon M. Selckmann of the Interstate Commission on the Potomac River Basin. Researchers incorporated field samples collected as part of an ongoing investigation into harmful algal blooms in the Shenandoah River supported by the Virginia Department of Environmental Quality and the commission.

The team has presented its findings at several scientific conferences, including the Society for Freshwater Science Annual Meeting, the Potomac River Conference and the 2025 Biennial Coastal and Estuarine Research Federation Meeting in Richmond.

Christova said the grant funding played a critical role in launching her laboratory and expanding research opportunities for students.

"The 4-VA@Mason funding was very important to me, as it supported the establishment of my research lab, fostered the development of regional and international research collaborations, and provided funding for undergraduate and graduate students interested in aquatic and cyanobacterial research," she said.