About this Research Topic
Nitrate pollution of aquatic environments is a problem of global relevance. Excess of nitrogen compounds in the environment may lead to eutrophication of surface waters and negatively impact the quality of groundwater, which serves as drinking water resource to a large fraction of the global population. Microbial processes such as denitrification, anaerobic ammonia oxidation (anammox) or dissimilatory nitrate reduction to ammonium (DNRA) contribute to the control of nitrate in surface waters and aquifers. While denitrification and anammox result in the formation of gaseous nitrogen compounds and thus in the removal of fixed nitrogen from the environment, DNRA leads to nitrogen conservation but may also provide ammonium for the anammox process. However, the interplay of denitrification, anammox, and DNRA and the environmental factors that control them are still poorly understood.
In this Research Topic, we would like to stimulate publications from the fields of environmental microbiology, microbial ecology, biogeochemistry, geomicrobiology, and molecular microbiology to increase our understanding of microbial processes in surface freshwaters and groundwater leading to either removal of fixed nitrogen by denitrification or anammox, or to conservation of nitrogen as ammonium by DNRA. The goal is to get an overview of which factors or combination of factors - including geological settings, land use intensity, availability of suitable electron donors, presence of oxygen, lake or groundwater depth and residence times - promote either denitrification, anammox, or DNRA. In this context, we want to learn to what extent these microbial processes could be promoted by changes in land use practices or other human controls. We also invite contributions that report on novel microbial players involved in anaerobic nitrogen transformation processes and their interactions with other microbial populations or players of the nitrogen cycle.
This Research Topic focuses on studies (including, e. g., original research, perspectives, minireviews, commentaries and opinion papers) that investigate and discuss:
• Microbial communities involved in anaerobic nitrogen transformation processes in surface waters or aquifers.
• Rates of anaerobic nitrogen transformation processes in surface waters or aquifers.
• Nitrogen fluxes between different compartments of freshwater ecosystems.
• Co-occurrence of and links between denitrification, anammox, and DNRA.
• Competition and niche differentiation between denitrification, anammox, and DNRA.
• Environmental factors controlling denitrification, anammox, and DNRA and their interplay.
• Links between anaerobic and aerobic nitrogen transformation processes and the respective microbial communities.
• Impact of human activities such as land use intensity on anaerobic nitrogen transformation processes in surface waters or groundwater.
• Identification of novel players in denitrification, anammox, or DNRA by cultivation or (meta-)genomics approaches.
Keywords: denitrification, anammox, DNRA, groundwater
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