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Updated: Jul 8, 2026
06:42
Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment
Published on: July 22, 2019
Does microorganism stoichiometry predict microbial food web interactions after a phosphorus pulse?
Presentación Carrillo1, Manuel Villar-Argaiz, Juan M Medina-Sánchez
1Instituto del Agua, Universidad de Granada, 18071, Granada, Spain. pcl@ugr.es
Microbial Ecology
|January 1, 2008
Summary
Atmospheric nutrient loads impact aquatic microbial food webs. Phosphorus enrichment affects algae more than bacteria, influencing ciliate development through nutrient competition.
Area of Science:
- Aquatic microbial ecology
- Limnology
- Nutrient cycling
Background:
- Understanding aquatic food web dynamics in pristine ecosystems requires knowledge of microbial interactions influenced by atmospheric nutrient deposition.
- Nitrogen and phosphorus (N/P) ratios are critical factors affecting these interactions.
Purpose of the Study:
- To investigate the effects of varying atmospheric N/P ratios on microbial food web interactions in a high-mountain lake.
- To determine the role of nutrient availability and stoichiometry in regulating algae-bacteria relationships and ciliate development.
Main Methods:
- In situ experiments mimicking atmospheric nutrient inputs at different N/P ratios were conducted over seasonal succession in a pelagic lake zone.
- Measurements included algal and bacterial abundance, biomass, biovolume, P-incorporation rates, P-cell quota, and N/P ratios.
Main Results:
- Algae responded significantly to phosphorus enrichment, showing changes in abundance, biomass, and P-dynamics, while heterotrophic bacteria remained less affected.
- Ciliate development was limited by phosphorus deficiency in bacteria, often caused by algal P-uptake, especially when bacterial N/P ratios exceeded 20-24.
- Optimal ciliate development occurred when bacteria were phosphorus-rich (N/P < 20) and algae approached Redfield proportions (N/P ≈ 16).
Conclusions:
- Algae and bacteria shifted from commensalistic-mutualistic to competitive relationships for phosphorus under increasing bacterial P-deficiency.
- The bacterial N/P ratio is a key indicator for understanding algae-bacteria dynamics and microbial food web development.
- Bacterial N/P thresholds can be used to diagnose ciliate development, highlighting an understudied aspect of microbial ecology.
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