Award: OCE-2219548

Seagrasses form highly productive coastal ecosystems that provide habitat for marine life, stabilize sediments, improve water quality, and store carbon. Despite their ecological importance, seagrass populations are declining worldwide as a result of multiple environmental stressors. An important but comparatively understudied component of seagrass health is the role of microorganisms, including viruses and other pathogens, and how interactions between seagrasses and these microorganisms are affected by changing environmental conditions.

This project sought to advance our understanding of these interactions using turtlegrass (Thalassia testudinum), one of the dominant seagrasses of the subtropical western Atlantic and Caribbean. A major component of the original project focused on Turtlegrass virus X (TVX), one of the first viruses identified from a marine flowering plant. Collaborators at the University of South Florida developed experimental approaches for studying TVX infection and examined how turtlegrass responds to viral infection under different environmental conditions, including changes in salinity and temperature. RNA sequencing was used to characterize changes in gene activity associated with infection and environmental stress. Complementary quantitative proteomic analyses were also initiated to determine how these changes are reflected in the proteins responsible for cellular structure, metabolism, stress responses, and defense. Together, these approaches are helping establish one of the first experimental frameworks for investigating virus–host interactions in a marine flowering plant.

During the project, research was also expanded to investigate interactions between turtlegrass and pathogenic Labyrinthula, the microorganism responsible for seagrass wasting disease. This disease has affected seagrass populations throughout the world, yet the cellular mechanisms used by seagrasses to respond to infection remain poorly understood. Our experiments demonstrated that turtlegrass mounts a highly coordinated defense response following infection. This response involves the production of reactive oxygen species and nitric oxide, changes in cellular respiration, activation of enzymes associated with programmed cell death, and changes in metabolites involved in plant defense. Notably, this study provided the first evidence of nitric oxide production by a marine flowering plant in the context of a plant–pathogen interaction. The results indicate that the visible lesions characteristic of seagrass wasting disease result not only from damage caused directly by the pathogen but also from a coordinated defense response by the plant itself.

We also examined how Labyrinthula infections vary naturally through time in Tampa Bay, Florida. Field surveys combined with molecular detection methods revealed that pathogenic Labyrinthula can be widespread even in turtlegrass leaves that show no visible signs of disease. Pathogen abundance peaked during favorable growing conditions in May 2024 and subsequently declined following hurricane disturbance. Three hurricanes (Debby, Helene, and Milton) affected the region during the study period, providing an unusual opportunity to examine disease dynamics in the context of major environmental disturbances. These findings suggest that hurricane-associated changes in freshwater input, salinity, water movement, and host condition can alter interactions between turtlegrass and its pathogens. Understanding these relationships is increasingly important as coastal ecosystems experience both chronic environmental change and acute extreme-weather events.

Beyond these scientific findings, the project contributed to the training and professional development of graduate and undergraduate students in marine ecology, molecular biology, plant physiology, bioinformatics, and quantitative approaches. Students participated in field and laboratory research and the communication of results to scientific and public audiences. Project findings have been disseminated through scientific presentations, peer-reviewed publications, and publicly accessible datasets. Research data have been deposited with the Biological and Chemical Oceanography Data Management Office (BCO-DMO), ensuring their long-term availability to the scientific community and the public.

Collectively, this project has expanded knowledge of an understudied dimension of marine plant biology: how seagrasses interact with microbial pathogens and how those interactions are influenced by environmental conditions. By advancing experimental systems for studying both viral infection and seagrass wasting disease, the project provides new tools and knowledge for understanding the resilience of ecologically important seagrass ecosystems in a changing environment.

 

Last Modified: 08/07/2026
Modified by: Cliff Ross