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Updated: Jun 21, 2026
08:43
Aerobic Biodegradation Testing of Materials Using a Natural Marine Seawater Inoculum and Closed Loop Respirometer
Published on: October 24, 2025
Microbial community response to seawater amendment in low-salinity tidal sediments
Jennifer W Edmonds1, Nathaniel B Weston, Samantha B Joye
1Department of Biological Sciences, University of Alabama, Box 870206, Tuscaloosa, AL 35487-0206, USA. jwedmonds@bama.ua.edu
Microbial Ecology
|July 25, 2009
Summary
Seawater intrusion into freshwater sediments alters microbial metabolism, not community structure. Changes in microbial activity over weeks are driven by gene expression, not shifts in bacterial or archaeal populations.
Area of Science:
- Environmental microbiology
- Coastal ecology
- Biogeochemistry
Background:
- Coastal freshwater ecosystems face increasing salinity due to rising sea levels and upstream water withdrawals.
- Microbial community and functional responses to seawater intrusion in these environments are poorly understood.
- Previous research documented biogeochemical shifts in response to salinity changes.
Purpose of the Study:
- To investigate the impact of controlled porewater salinity increases on prokaryotic community structure in freshwater sediments.
- To determine if microbial community composition changes in response to simulated seawater intrusion.
- To explore the relationship between microbial activity and community structure under varying salinity.
Main Methods:
- Utilized molecular approaches, including terminal restriction fragment length polymorphism and 16S rRNA gene sequencing.
- Analyzed sediment microbial communities from freshwater cores exposed to controlled increases in salinity over 35 days.
- Compared microbial community composition between control and seawater-amended treatments at multiple time points.
Main Results:
- Significant changes in microbial activity, including altered mineralization pathways (decreased methanogenesis, increased iron and sulfate reduction), were observed.
- Despite biogeochemical shifts, no significant differences in bacterial or archaeal community composition were detected between control and saline treatments.
- The microbial community in saline-treated sediments did not become more marine-like over the experimental period.
Conclusions:
- Changes in microbial metabolic activity and carbon mineralization in response to short-term salinity increases are primarily regulated by shifts in gene expression, not by alterations in microbial community composition.
- Freshwater microbial communities exhibit resilience in composition despite functional shifts under moderate salinity intrusion.
- This suggests a rapid physiological adaptation mechanism in microbes rather than a community-level replacement response.
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