Work

Contrasting spatial patterns of antibiotics and antibiotic resistance genes in surface sediments along the Yangtze river

Year: 2026

Type: article

Abstract: Antibiotics and antibiotic resistance genes (ARGs) are emerging contaminants of concern in large-river sediments, yet their spatial covariation across dam-regulated river systems remains poorly understood. To address this question, surface sediments were collected along the main stem of the Yangtze River, covering the upstream reach, the Three Gorges Reservoir (TGR), the middle reach, and the downstream reach. Of the 44 target antibiotics, 35 were detected. Metagenomic analysis of 15 samples with usable sequencing datasets identified 828 putative ARG subtypes, among which 23 representative subtypes were selected for detailed spatial comparison. Tetracyclines accounted for more than 90% of the total antibiotic burden, with mean concentrations decreasing from 82.97 ng/g upstream to 70.81 ng/g in the TGR, and 49.22 ng/g downstream. In contrast, the summed abundance of the 23 selected ARGs was higher downstream (68867 RPKM) than upstream (48377 RPKM), demonstrating incomplete spatial concordance between antibiotic residues and the sediment resistome. Exploratory multivariate analyses indicated that ARGs variation was jointly associated with sediment properties, antibiotic residues, microbial communities, and MGEs. The PLS-PM showed positive direct path coefficients from antibiotics (β = 0.390), MGEs (β = 0.334), and sediment properties (β = 0.306) to ARGs. Pseudomonadota- and Nitrospirota-affiliated metagenome-assembled genomes were identified as potential ARGs hosts. Positive associations between ARGs and mobile genetic elements suggested elevated genetic mobility potential within the sediment resistome. Risk assessment identified tetracycline as the principal antibiotic-related ecological concern, with a maximum hazard quotient of 18.9 in the TGR, whereas the evaluated ARGs remained within the lowest potential human-health risk rank. These findings demonstrate contrasting spatial patterns of antibiotics and ARGs along the Yangtze River and identify sediment properties, microbial communities, and genetic mobility potential as important correlates of ARGs variation.

Source: Emerging contaminants

DOI: 10.1016/j.emcon.2026.100774