Flowthrough reactor flasks for study of microbial metabolism in sediments

Area of Science:

• Environmental Microbiology
• Geochemistry
• Aquatic Ecosystems

Background:

• Anoxic sediments are critical environments for biogeochemical cycling.
• Understanding microbial responses to nutrient inputs in sediments is vital for aquatic ecosystem health.
• Previous methods often diluted sediment samples, hindering accurate rate measurements.

Purpose of the Study:

• To develop and validate a flowthrough reactor system for continuous nutrient addition to anoxic sediments without dilution.
• To investigate the relationship between sulfate reduction and methane production under varying nutrient conditions.
• To assess the impact of acetate and sulfate inputs on microbial processes in freshwater lake sediments.

Main Methods:

• Utilized novel flowthrough reactor flasks designed for continuous, low-level nutrient infusion.
• Simulated sulfate and acetate inputs into mixed anoxic sediments from a freshwater eutrophic lake.
• Monitored methane production and sulfate consumption rates over a 12-day incubation period post-adaptation.

Main Results:

• The reactor system maintained constant rates of methane production and sulfate consumption after a 2-day adaptation.
• A sulfate input of 0.15 mmol/liter/day was matched by an equivalent sulfate removal rate, unaffected by acetate.
• Acetate addition doubled methane production in controls, while sulfate consumption required high sulfate and acetate concentrations for stimulation.

Conclusions:

• The flowthrough reactor system effectively maintains the balance between sulfate reduction and methane production in freshwater sediments.
• This system is a valuable tool for studying sediment microbial community responses to controlled additions of substrates, inhibitors, or xenobiotics.
• Findings highlight the distinct regulatory mechanisms for methane production and sulfate reduction in response to varying nutrient loads.