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Research article2022Peer reviewedOpen access

The role of organic matter and microbial community controlling nitrate reduction under elevated ferrous iron concentrations in boreal lake sediments

Jantti, Helena; Jilbert, Tom; Aalto, Sanni L.; Simojoki, Asko; Mangayil, Rahul; Peura, Sari; Rissanen, Antti J.


The nitrogen availability, that affects the greenhouse gas emission and the trophic level of lakes, is controlled mainly by microbial processes. We measured in a boreal nitrate and iron rich lake how the rates of potential denitrification and dissimilatory nitrate reduction to ammonia (DNRA) are affected by degradability of organic matter and availability of aqueous ferrous iron. We also investigated the microbial community by using 16S rRNA gene and shotgun metagenomic sequencing approach, which allows taxonomic analyses and detection of metagenome-assembled genomes (MAGs) containing genes for both nitrate reduction and iron oxidation. The results show that truncated denitrification, leading to release of nitrous oxide, is favored over dinitrogen production in conditions where the degradability of the organic matter is low. DNRA rates were always minor compared to denitrification and appeared to be independent of the degradability of organic carbon. Reduced iron stimulated nitrate reducing processes, although consistently only DNRA. However, the proportion of MAGs containing DNRA genes was low suggesting chemistry driven stimulation by reduced iron. Nevertheless, the metagenomic analyses revealed unique taxa genetically capable of oxidizing iron and reducing nitrate simultaneously. Overall, the results highlight the spatial variability in microbial community and nitrous oxide emissions in boreal lake sediments.


Boreal lake; Iron; Microbial community; Nitrate reduction; Nitrogen; Nitrous oxide; Sediment

Published in

2022, Volume: 849, number: 9, pages: 2145-2160
Publisher: SPRINGER

    Sustainable Development Goals

    SDG15 Life on land

    UKÄ Subject classification

    Agricultural Science

    Publication identifier


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