The groundbreaking research conducted by the University of Tennessee, Knoxville, in collaboration with the University of Maryland, reveals an astonishing truth about our ocean ecosystems: viral infections in blue-green algae, also known as cyanobacteria, can actually enhance productivity and contribute to a vital layer of oxygen in marine environments.
As Steven Wilhelm, the Kenneth and Blaire Mossman Professor in UT's Department of Microbiology and one of the senior authors of the study, eloquently stated, "We live on a microbial planet, and viruses are integral to this process." He emphasizes that the role of viruses is not solely linked to causing illness; they also play a crucial part in stimulating growth and supporting production within these ecosystems.
Wilhelm took the helm as chief scientist during a National Science Foundation research expedition to the Sargasso Sea, which ultimately led to the publication of their findings in the esteemed journal, Nature Communications. The research team comprised four faculty members and three students from UT, alongside collaborators from prestigious institutions such as the Georgia Institute of Technology, Ohio State University, Technion Institute of Technology in Israel, and the University of Maryland.
During their voyage aboard the research vessel Atlantic Explorer in October 2019, the team conducted continuous RNA sequencing surveys of microbiological data at the Bermuda Atlantic Time-series Study, a project that has been gathering extensive physical, biological, and chemical information about the ocean for nearly forty years.
The study indicates that when cyanobacteria, specifically Prochlorococcus, become infected by viruses, they release nutrients that subsequently stimulate microbial growth, leading to increased levels of oxygen found several meters beneath the ocean's surface. Wilhelm shared his insights, stating, "Our observations suggest that this band of oxygen-rich water, located about fifty meters below the surface and persisting for several months each year, is at least partially driven by viral activity."
The research establishes a substantial connection between two fundamental concepts in oceanography: the "viral shunt," a term first introduced by Wilhelm and Curtis Suttle from the University of British Columbia back in 1999, and the microbial loop, which is essential to the ocean’s food web.
Joshua S. Weitz, a biology professor at the University of Maryland, elaborated on the study's methodology, explaining, "By analyzing extensive data on cellular and viral activities across day and night cycles, including the infection status and prevalence of viruses impacting cyanobacteria, we can discern the widespread effects of viral infections on a systemic scale. Viral infections seem to promote the recycling of carbon and nutrients by other microbes, thereby boosting productivity and revealing historical patterns that suggest a relationship between viral activity and the functionality of ecosystems below the ocean’s surface."
The RNA sequencing and further analyses were performed at the University of Tennessee. The leading author of the paper is Naomi Gilbert (PhD ’22), with contributions from other UT scholars including Wilhelm, microbiology Professor Alison Buchan, Assistant Professor Gary LeCleir, and Professor Jennifer DeBruyn from the Department of Biosystems Engineering and Soil Science, along with former UT students Helena Pound (PhD ’21) and Shelby Cagle (’21).
This pivotal study was spearheaded by Wilhelm and Weitz, funded through a National Science Foundation Collaborative Research grant, and received additional support from the Simons Foundation and other organizations.
For those eager to learn more about this cutting-edge research, Wilhelm and Weitz will be sharing insights in an upcoming article featured in The Conversation.
Published in Nature Communications, the article titled "Seasonal enhancement of the viral shunt catalyzes a subsurface oxygen maximum in the Sargasso Sea" was released on December 6, 2025.
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