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

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

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Abstract

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.

Original languageEnglish
Number of pages16
JournalHYDROBIOLOGIA
Volume849
Issue number9
DOIs
Publication statusPublished - 2022
Publication typeA1 Journal article-refereed

Keywords

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

Publication forum classification

  • Publication forum level 1

ASJC Scopus subject areas

  • Aquatic Science

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