A New Study Unveils How Viruses Influence Oceanic Oxygen Levels
Recent research from the University of Tennessee, Knoxville, in partnership with the University of Maryland, has uncovered a fascinating relationship between viral infections in blue-green algae and ocean productivity, highlighting their role in enriching oxygen levels in marine ecosystems.
"We inhabit a planet dominated by microbes, and viruses play a crucial role in this dynamic," explained Steven Wilhelm, the Kenneth and Blaire Mossman Professor in the Department of Microbiology at UT and a senior author of the study. "Interestingly, their impact often involves promoting growth rather than merely causing disease."
Wilhelm led the research during a National Science Foundation cruise to the Sargasso Sea, which resulted in findings published in the esteemed journal Nature Communications (https://www.nature.com/articles/s41467-025-67002-1). The research team included four UT faculty members, three students, and collaborators from institutions such as Georgia Institute of Technology, Ohio State University, Technion Institute of Technology in Israel, and the University of Maryland.
While aboard the research vessel Atlantic Explorer in October 2019, the team conducted continuous RNA sequencing surveys at the Bermuda Atlantic Time-series Study (https://bios.asu.edu/bats), a long-running project that has been gathering vital physical, biological, and chemical ocean data for nearly forty years.
The study reveals that when cyanobacteria, specifically Prochlorococcus, are infected by viruses, they release essential nutrients that promote microbial growth, leading to increased oxygen levels located several meters beneath the ocean's surface.
"Our findings indicate that this significant layer of oxygenated water, which can be found about 50 meters below the surface for several months of the year, is partially influenced by viral activity," Wilhelm stated.
This research establishes a clear connection between two key concepts in oceanography: the "viral shunt" (first described by Wilhelm and Curtis Suttle from the University of British Columbia in 1999) and the microbial loop within the ocean’s food web.
"By examining large-scale data on both cellular and viral activities through day and night cycles, including the prevalence of viruses that infect cyanobacteria, we can decipher the extensive effects of viral infections on a system-wide scale," noted Joshua S. Weitz, a biology professor at the University of Maryland. "Virus infections seem to enhance the recycling of carbon and nutrients among other microbes, which drives productivity and sheds light on historical patterns linking viral activity to ecosystem functions beneath the surface."
The RNA sequencing and related analyses were carried out at the University of Tennessee, with Naomi Gilbert (PhD '22) serving as the lead author. Other contributors from UT include microbiology Professors Alison Buchan and Gary LeCleir, Jennifer DeBruyn from the Department of Biosystems Engineering and Soil Science, and former students Helena Pound (PhD '21) and Shelby Cagle ('21).
This collaborative study, spearheaded by Wilhelm and Weitz, received funding from a National Science Foundation Collaborative Research grant and was supported by the Simons Foundation, among others.
Stay tuned, as Wilhelm and Weitz will delve deeper into their findings in an upcoming article for The Conversation (https://theconversation.com/institutions/university-of-tennessee-688).
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