Ecological dynamics explain modular denitrification in the ocean

• 成果类型: Article
• 署名作者: Sun, Xin; Buchanan, Pearse J.; Zhang, Irene H.; San Roman, Magdalena; Babbin, Andrew R.; Zakem, Emily J.
• 署名单位: Carnegie Institution for Science; Commonwealth Scientific & Industrial Research Organisation (CSIRO); Massachusetts Institute of Technology (MIT); University of Southern California; University of Salamanca; Consejo Superior de Investigaciones Cientificas (CSIC); CSIC-USAL - Instituto de Biologia Funcional y Genomica (IBFG)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14120
• DOI: 10.1073/pnas.2417421121
• 发表日期: 2024-12-24
• 关键词: nitrous-oxide production; oxygen minimum; complete nitrification; nitrite oxidation; organic-carbon; water column; north; bacteria; nitrate; flux

摘要

Microorganisms in marine oxygen minimum zones (OMZs) drive globally impactful biogeochemical processes. One such process is multistep denitrification (NO3--NO2 -- NO- N 2 O- N 2 ), which dominates OMZ bioavailable nitrogen (N) loss and nitrous oxide (N2O) production. Denitrification- derived N loss is typically measured and modeled as a single step, but observations reveal that most denitrifiers in OMZs contain subsets (modules) of the complete pathway. Here, we identify the ecological mechanisms sustaining diverse denitrifiers, explain the prevalence of certain modules, and examine the implications for N loss. We describe microbial functional types carrying out diverse denitrification modules by their underlying redox chemistry, constraining their traits with thermodynamics and pathway length penalties, in an idealized OMZ ecosystem model. Biomass yields of single- step modules increase along the denitrification pathway when organic matter (OM) limits growth, which explains the viability of populations respiring NO2- and N2O in a NO3--filled ocean. Results predict denitrifier community succession along environmental gradients: Pathway length increases as the limiting substrate shifts from OM to N, suggesting a niche for the short NO3--NO2- module in free- living, OM- limited communities, and for the complete pathway in organic particle- associated communities, consistent with observations. The model captures and mechanistically explains the observed dominance and higher oxygen tolerance of the NO3--NO2 - module. Results also capture observations that NO3- is the dominant source of N2O. Our framework advances the mechanistic understanding of the relationship between microbial ecology and N loss in the ocean and can be extended to other processes and environments.