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Microbial community dynamics in Mediterranean nutrient-enriched seawater mesocosms: changes in abundances, activity
FEMS Microbiology Ecology
|January 4, 2001
Summary
Nutrient addition increased bacterial densities in the Mediterranean Sea, but protozoan grazing controlled populations. Grazing pressure altered bacterial size, activity, and taxonomic composition, favoring larger cells and specific bacterial groups.
Area of Science:
- Marine microbiology
- Bacterial ecology
- Oceanography
Background:
- Bacterial communities are crucial to marine ecosystems.
- Understanding their response to nutrient changes and predation is vital.
Purpose of the Study:
- To investigate quantitative and qualitative changes in Mediterranean Sea bacterial communities.
- To assess the impact of inorganic nutrient addition and protozoan grazing.
Main Methods:
- Utilized traditional microbial ecology, molecular biology, and flow cytometry.
- Compared duplicate batch mesocosms with and without nutrient enrichment.
- Analyzed bacterial abundances, production, cell size, activity, culturability, and taxonomic diversity.
Main Results:
- Nutrient addition and confinement increased bacterial densities, rapidly controlled by grazing.
- Bacterial activity and morphology shifted during growth and under grazing pressure.
- Grazing preferentially consumed medium-sized, culturable cells, limiting production and favoring larger cells.
- Grazing impacted taxonomic composition, reducing gamma-Proteobacteria while preserving alpha-Proteobacteria.
Conclusions:
- Protozoan grazing significantly shapes bacterial community structure and function in nutrient-enriched marine environments.
- Bacterial size, activity, and culturability are key factors influencing predator-prey dynamics.
- Specific bacterial taxa, like Ruegeria and Cytophaga, may possess defense mechanisms against grazing.
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