Intertidal epilithic bacteria diversity changes along a naturally occurring carbon dioxide and pH gradient

Area of Science:

• Marine microbiology
• Coastal ecology
• Oceanography

Background:

• Intertidal epilithic bacteria are crucial for coastal ecosystems.
• Limited research exists on their diversity and response to environmental changes.
• Submarine CO2 seeps create localized, CO2-enriched seawater with lower pH.

Purpose of the Study:

• To test if epilithic bacteria communities change with varying seawater pH and CO2 levels.
• To assess the impact of ocean acidification on these microbial communities.

Main Methods:

• Biofilms were collected from three sites with differing pH/CO2 levels at Levante Bay, Italy.
• High-throughput sequencing of 16S rRNA genes was used to determine bacterial diversity.
• Seawater pCO2 levels ranged from ambient to 1654 μatm, simulating future ocean conditions.

Main Results:

• Alpha diversity of total bacteria and Cyanobacteria communities differed significantly between sites (anova P < 0.05).
• Bacteria and Cyanobacteria communities showed significant differences across sites (anosim/permanova P < 0.01).
• Proteobacteria, Bacteroidetes, and Cyanobacteria were dominant, but relative abundance of specific orders varied.

Conclusions:

• Bacterial diversity in intertidal epilithic communities is significantly altered by seawater pH/CO2 gradients.
• Findings highlight the impact of ocean acidification on coastal microbial ecosystems.
• This study provides detailed insights for evaluating future ocean acidification effects.