Genetic and environmental controls on nitrous oxide accumulation in lakes
Jatta Saarenheimo1, Antti J Rissanen1, Lauri Arvola2
1Department of Biological and Environmental Science, University of Jyväskylä, 40014, Jyväskylä, Finland.
Plos One
|March 11, 2015
Summary
Nitrous oxide (N2O) accumulation in boreal lakes is linked to the balance of genes responsible for denitrification. Higher nitrate levels influence this balance, impacting N2O levels in lake ecosystems.
Area of Science:
- Environmental microbiology
- Biogeochemistry
- Limnology
Background:
- Nitrous oxide (N2O) is a potent greenhouse gas with significant contributions from aquatic ecosystems.
- Denitrification, the microbial process reducing nitrate to N2O and nitrogen gas, is a key N2O source.
- Understanding the microbial and environmental drivers of N2O accumulation in lakes is crucial for predicting climate impacts.
Purpose of the Study:
- To investigate the relationship between environmental factors, N2O accumulation, and the genetic potential for denitrification in boreal lakes.
- To quantify the abundance of key denitrification genes (nirS, nirK, nosZ) and their relationship to N2O levels.
- To determine the role of nitrate availability in modulating N2O production and the balance of denitrification genes.
Main Methods:
- Sampling of lake sediments from 12 boreal lakes and one detailed depth transect.
- Quantification of bacterial genes encoding nitrite reductase (nirS/nirK) and nitrous oxide reductase (nosZ, including nosZI and nosZII) using molecular methods.
- Measurement of in-situ N2O accumulation and hypolimnetic nitrate concentrations.
Main Results:
- Summertime N2O accumulation and hypolimnetic nitrate concentrations were positively correlated across lakes and within a depth profile.
- Significant inter-lake variability in nirS, nirK, nosZI, and nosZII gene abundances was observed.
- The ratio of nitrite reductase genes to N2O reductase genes ((nirS+nirK)/nosZI) correlated with N2O accumulation and nitrate availability.
Conclusions:
- The relative abundance of nitrite versus N2O reductase genes is a key factor controlling N2O accumulation in lake sediments.
- Nitrate availability modulates N2O accumulation by influencing both the overall rate of denitrification and the balance of microbial functional genes.
- These findings highlight the importance of microbial genetic potential and nutrient status in regulating greenhouse gas emissions from aquatic environments.
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