Defining Site-Specific Water Quality Guidelines for Marine Microbiomes under Contaminant Stress.

Area of Science:

• Marine microbiology
• Ecotoxicology
• Conservation science

Background:

• Marine ecosystem resilience is linked to microbiome health.
• Prokaryotes are often overlooked in conservation due to challenges in defining microbial sensitivity thresholds.
• Existing regulatory frameworks primarily focus on eukaryotic organisms.

Purpose of the Study:

• To develop a quantitative method for assessing marine microbial responses to contamination stress.
• To derive microbiome hazard concentrations compatible with existing regulatory frameworks.
• To evaluate copper sensitivity in marine microbiomes across a disturbance gradient.

Main Methods:

• Combined 16S rRNA gene amplicon sequencing with ecotoxicological concentration-response modeling.
• Utilized propidium monoazide and flow cytometry to quantify intact microbial cells and determine absolute abundances.
• Derived no-significant-effect concentration values for individual taxa and calculated microbiome hazard concentrations.

Main Results:

• Developed a novel approach to quantitatively define microbial sensitivity thresholds.
• Derived site-specific microbiome hazard concentrations for copper, ranging from 0.10 to 0.94 μg L^-1 for 5% of community taxa.
• Observed higher copper sensitivities in microbiomes from ecologically valuable sites (e.g., coral reefs) compared to disturbed areas.

Conclusions:

• Marine microbiomes exhibit varying sensitivities to contaminants, with ecologically valuable sites showing greater sensitivity.
• The developed quantitative approach enables direct integration of microbiome sensitivity data into environmental risk assessments.
• Stricter environmental protection is needed for ecologically valuable marine sites to preserve microbiome health and ecosystem resilience.