Winogradsky column — Which statement best describes the purpose of this model ecosystem used in environmental microbiology teaching and research?

Introduction / Context:
A Winogradsky column is a self-contained stratified ecosystem that develops chemical and biological gradients, allowing visualization of how microbial metabolisms are organized by availability of light, oxygen, and sulfur compounds. It is a discovery tool for teaching biogeochemical cycling.

Given Data / Assumptions:

• The model uses sediment, a carbon source (e.g., cellulose), and a sulfur source (e.g., calcium sulfate), illuminated over time.
• Gradients form: oxic at the top to anoxic/sulfidic at the bottom.
• The question seeks the correct description of what a Winogradsky column demonstrates.

Concept / Approach:
Its primary purpose is to show microbial succession and niche partitioning along environmental gradients. It is not a filtration device for removing microbes from samples, oceanic or terrestrial.

Step-by-Step Solution:

Verification / Alternative check:
Phototroph color bands and layered anaerobic/fermentative communities visibly appear over weeks, confirming gradient-driven selection.

Why Other Options Are Wrong:

• Filtering claims: a Winogradsky column is not a filtration apparatus.
• “Both (a) and (b)”: contains an incorrect component, so cannot be correct.

Common Pitfalls:
Equating “column” with chromatography or filtration; here, the column is an ecological incubator, not a separation device.

Final Answer:
A Winogradsky column is used to demonstrate interactions and gradients that occur in aquatic environments