Salinity and nutrient availability dictate methane production and its temperature sensitivity in lakes

Area of Science:

• Environmental Science
• Geochemistry
• Microbiology

Background:

• Lakes are significant sources of methane (CH4) emissions, yet the factors influencing these emissions are not fully understood.
• Anthropogenic activities and climate change can alter lake conditions, potentially increasing methane production.

Purpose of the Study:

• To investigate the interactive effects of salinity, nutrient status, and temperature on methane production driven by different substrates (formate, acetate, methanol) in lake sediments.
• To determine how these factors influence the temperature sensitivity of methanogenesis.

Main Methods:

• Microcosm experiments using sediments from 10 lakes with varying salinity (0.25-180 g L-1) and nutrient levels.
• Controlled incubation at 8°C and 18°C with additions of formate, acetate, and methanol.
• Analysis of methane production rates and temperature sensitivity (Q10).

Main Results:

• In nutrient-rich freshwater lakes, acetate addition most significantly increased methane production.
• In nutrient-poor saline lakes, only methanol addition stimulated methane production.
• Substrate availability amplified temperature sensitivity, with salinity, nutrients, and methanol concentration being key drivers for formate, acetate, and methanol treatments, respectively.

Conclusions:

• Methane production and its temperature sensitivity in lake sediments are complexly regulated by substrate type, salinity, and nutrient status.
• Future climate change, altering lake temperatures, salinities, and nutrient inputs, may lead to increased methane emissions from lakes due to heightened sensitivity.