In a groundbreaking study, researchers from the University of Tennessee, Knoxville, and the University of Maryland have discovered that viral infections of blue-green algae in the ocean enhance ecosystem productivity and contribute significantly to oxygen levels. This research, published in Nature Communications, highlights the complex role of viruses in oceanic ecosystems.
“It is really a microbial planet we live on, and viruses are part of that process,” stated Steven Wilhelm, the Kenneth and Blaire Mossman Professor in UT’s Department of Microbiology and one of the study’s senior authors. “Sometimes their activity is as much about stimulating growth and production as it is about sickness and disease.”
Exploring the Sargasso Sea
Wilhelm led a National Science Foundation-funded research cruise to the Sargasso Sea, which formed the basis of this study. The team, comprising four UT faculty members and three students, collaborated with experts from the Georgia Institute of Technology, Ohio State University, Technion Institute of Technology in Israel, and the University of Maryland.
Onboard the research vessel Atlantic Explorer in October 2019, the team conducted continuous RNA sequencing surveys at the Bermuda Atlantic Time-series Study. This site has been a hub for collecting oceanic data for nearly four decades, providing invaluable insights into physical, biological, and chemical processes.
The Role of Viruses in Oceanic Oxygen Production
The study reveals that viral infections of the cyanobacteria Prochlorococcus release nutrients that spur microbial growth, enhancing oxygen levels tens of meters below the ocean’s surface. “The observations suggest this meters-wide ribbon of oxygenated water that exists 50 meters below the surface for several months per year is at least in part driven by the virus activity,” Wilhelm explained.
This research establishes a direct connection between two critical oceanographic processes: the “viral shunt,” a concept first introduced by Wilhelm and Curtis Suttle in 1999, and the microbial loop within the ocean’s food web. The viral shunt refers to the process where viruses infect marine microorganisms, leading to the release of organic matter that fuels microbial growth.
Insights from Large-Scale Data
Biology Professor Joshua S. Weitz from the University of Maryland noted, “By analyzing large-scale data on cellular and viral activity over day-night cycles, including the infection status and abundances of viruses that infect cyanobacteria, we are able to identify the imprint of viral infections at system-scales.” He added that viral infections appear to enhance the recycling of carbon and nutrients, driving productivity and shedding new light on historical trends linking viral activity to ecosystem functioning below the surface.
“Viral infection appears to enhance the recycling of carbon and nutrients by other microbes, driving productivity and shedding new light on historical trends that indicate a link between viral activity and ecosystem functioning below the surface.” – Professor Joshua S. Weitz
Collaboration and Future Research
The RNA sequencing and additional analyses were completed at the University of Tennessee. Naomi Gilbert, who earned her PhD in 2022, is the lead author of the paper. Other contributors from UT include microbiology Professor Alison Buchan, Assistant Professor Gary LeCleir, Professor Jennifer DeBruyn from the Department of Biosystems Engineering and Soil Science, and former students Helena Pound and Shelby Cagle.
The study was primarily guided by Wilhelm and Weitz, with funding from a National Science Foundation Collaborative Research grant and support from the Simons Foundation, among others. The researchers plan to share more insights from their work in The Conversation.
This research underscores the intricate relationships within marine ecosystems and the pivotal role viruses play in maintaining oceanic health. As scientists continue to unravel these complex interactions, the findings could have significant implications for understanding global biogeochemical cycles and the health of marine environments.
