Eelgrass microbiome and disease dynamics under field and lab heat stress

Area of Science:

• Marine ecology
• Microbial ecology
• Ecosystem health

Background:

• Host-microbiome interactions are crucial for marine foundation species' disease resistance.
• Eelgrass wasting disease (Zostera marina) caused by Labyrinthula zosterae is a model for studying these interactions under environmental stress.

Purpose of the Study:

• To investigate how thermal stress affects eelgrass microbiome and wasting disease severity.
• To determine if L. zosterae isolates vary in virulence and impact on the host microbiome.
• To compare laboratory-observed microbiome responses to heat stress with field observations.

Main Methods:

• Laboratory experiments with eelgrass exposed to different temperatures (11°C vs. 19°C) and L. zosterae strains.
• Monitoring lesion development, pathogen load (qPCR), and microbiome composition (16S rRNA sequencing).
• Field surveys of intertidal eelgrass, monitoring tissue damage, growth, and microbiome dynamics before and after a natural heat stress event.

Main Results:

• Elevated temperatures significantly increased wasting disease severity in the lab, regardless of pathogen isolate.
• High temperatures induced microbiome dysbiosis, altering community composition and microbial taxa abundance (e.g., Colwelliaceae).
• Both lab and field heat stress reduced microbiome diversity, with field eelgrass showing tissue damage and reduced growth.

Conclusions:

• Warming temperatures accelerate Z. marina wasting disease, likely through microbiome disruption and/or compromised host defenses.
• Temperature is a primary driver of disease progression and microbiome shifts, more so than pathogen strain.
• Consistent trends of microbiome dysbiosis observed in both lab and field studies suggest temperature stress impacts eelgrass health and resilience.