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Seagrass meadows provide valuable ecosystem benefits but are at risk from disease. Eelgrass ( Zostera marina ) is a temperate species threatened by seagrass wasting disease (SWD), caused by the protist Labyrinthula zosterae . The pathogen is sensitive to warming ocean temperatures, prompting a need for greater understanding of the impacts on host health under climate change. Previous work demonstrates pathogen cultures grow faster under warmer laboratory conditions and documents positive correlations between warmer ocean temperatures and disease levels in nature. However, the consequences of disease outbreaks on eelgrass growth remain poorly understood. Here, we examined the effect of disease on eelgrass productivity in the field. We coupled in situ shoot marking with high-resolution imagery of eelgrass blades and used an artificial intelligence application to determine disease prevalence and severity from digital images. Comparisons of eelgrass growth and disease metrics showed that SWD impaired eelgrass growth and accumulation of non-structural carbon in the field. Blades with more severe disease had reduced growth rates, indicating that disease severity can limit plant growth. Disease severity and rhizome sugar content were also inversely related, suggesting that disease reduced belowground carbon accumulation. Finally, repeated measurements of diseased blades indicated that lesions can grow faster than healthy tissue in situ . This is the first study to demonstrate the negative impact of wasting disease on eelgrass health in a natural meadow. These results emphasize the importance of considering disease alongside other stressors to better predict the health and functioning of seagrass meadows in the Anthropocene.
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This content will become publicly available on December 1, 2025
Marine heatwaves and disease alter community metabolism and DOC fluxes on a widespread habitat-forming seagrass species (Zostera marina)
Climate change and disease are two major threats to maintaining healthy seagrass habitats. Seagrasses, and the ecosystems they support, play a critical ecological role in global carbon (C) cycles, providing key ecosystem services, such as blue carbon storage. Zostera marina (eelgrass), the most widespread seagrass species globally, is increasingly affected by warming and is also regularly infected by the endophytic pathogen Labyrinthula zosterae. Both stressors negatively impact plant physiology and population distributions, yet the effects of these stressors on C cycling, and particularly on C metabolism and dissolved organic carbon (DOC) fluxes in eelgrass, remain largely unexplored. Through a mesocosm experiment simulating a marine heatwave (MHW) followed by pathogen challenge with L. zosterae, it was observed that the simulated MHW initially decreased daily community DOC fluxes and Net Production Rates (NPR), while not changing Respiration Rates. DOC released into the water column at the end of the MHW also was less bioavailable than DOC from the control treatment. Importantly, community NPR recovered to control levels after the simulated MHW was over, demonstrating the community's resilience to warming. On the other hand, plants challenged with L. zosterae, which caused a significant decrease in aboveground biomass, exhibited significant decreases in DOC and NPR up to 20 days after the infection. These results have important implications in blue carbon processes, given that both stressors significantly impact the quantity and quality of DOC produced by Z. marina communities. These findings also highlight the differing levels of resilience of C cycling in this system by showing that the impacts of the simulated heat wave may be more transient when compared to the effects of disease.
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- Award ID(s):
- 2025457
- PAR ID:
- 10567147
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Science of The Total Environment
- Volume:
- 957
- Issue:
- C
- ISSN:
- 0048-9697
- Page Range / eLocation ID:
- 177820
- Subject(s) / Keyword(s):
- Blue carbon, Dissolved organic carbon, Eelgrass, Labyrinthula sp., Semi-labile carbon, Warming, Wasting disease
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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