Covariation of DOM molecular characteristics and bacterial carbon metabolism potential along a reservoir-agricultural river nutrient gradient.

Authors

Yue Jiang, Hongying Jiang, Yanhua Xie, Tianliang Zheng

Published in

Environmental geochemistry and health. Volume 48. Issue 16. Oct 18, 2026. Epub Oct 18, 2026.

Abstract

Agricultural nutrient loading is associated with variation in dissolved organic matter (DOM) composition and microbial communities across reservoir-agricultural river continuums, yet the covariation among nutrient conditions, DOM molecular heterogeneity, and bacterial metabolic potential remains insufficiently understood. This study integrated optical spectroscopy, ultrahigh-resolution mass spectrometry, nitrate dual-isotope tracing, end-member mixing analysis (EMMA), 16S rRNA sequencing, and metagenomic functional profiling to characterize DOM sources and composition and their associations with bacterial communities in a typical reservoir-agricultural river continuum. Our results showed that nitrogen and phosphorus enrichment within agricultural river reaches systematically rearranges DOM source apportionment, with relative abundance of humic-like components (C1, C3) rising alongside elevated abundances of heteroatomic molecular formulas (CHOS, CHONS) relative to oligotrophic reservoirs. Nutrient loading reshaped DOM via exogenous input of heteroatom-rich anthropogenic organics and boosted in-situ microbial humification. EMMA modeling further indicated that anthropogenic sources contributed 37.9% to riverine DOM. Principal coordinates analysis showed that reservoir-river community differentiation coincided with nutrient and fluorescent DOM gradients. Reservoir samples were dominated by Acinetobacter, Exiguobacterium, and Clade_III and showed higher relative abundances of several genes associated with carbohydrate and aromatic compound degradation. In contrast, river communities featured humic-adapted genera (Mycobacterium, hgcl_clade, Limnohabitans, and unclassified_Sporichthyaceae) and showed higher relative abundances of genes associated with lipid utilization and terrestrial-polymer degradation. This study highlighted coordinated spatial variation in nutrient conditions, DOM characteristics, bacterial community composition, and genomic carbon metabolism potential across the reservoir-agricultural river continuum, supplying theoretical guidance for pollution control and carbon cycling regulation in anthropogenic-disturbed inland water catchments.

PMID:
42893466
Bibliographic data and abstract were imported from PubMed on 19 Oct 2026.

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