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Salinity-driven trade-offs between nitrogen removal and microbiome dynamics in Fe-C-CWs toward saline aquaculture tailwater management.

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Title: Salinity-driven trade-offs between nitrogen removal and microbiome dynamics in Fe-C-CWs toward saline aquaculture tailwater management.
Authors: Ma X; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China; Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Jiangsu Ocean University, Lianyungang 222005, PR China; Key Laboratory of Coastal Salt Marsh Ecology and Resources, Ministry of Natural Resources, Jiangsu Ocean University, Lianyungang 222005, PR China. Electronic address: marianna_iocas@163.com., Zhai T; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China., Bao X; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China., Wu Z; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China., Yang Y; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China., Yin R; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China., Cai C; Jiangsu Key Laboratory of Marine Biotechnology, Jiangsu Ocean University, Lianyungang 222005, China., Liu G; College of Bio-systems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China; Ocean Academy, Zhejiang University, Zhoushan, 316021, China. Electronic address: liugang83@zju.edu.cn.
Source: Water research [Water Res] 2025 Dec 01; Vol. 287 (Pt B), pp. 124519. Date of Electronic Publication: 2025 Aug 31.
Publication Type: Journal Article
Language: English
Journal Info: Publisher: Pergamon Press Country of Publication: England NLM ID: 0105072 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1879-2448 (Electronic) Linking ISSN: 00431354 NLM ISO Abbreviation: Water Res Subsets: MEDLINE
Imprint Name(s): Original Publication: Oxford, Pergamon Press.
MeSH Terms: Salinity* , Nitrogen* , Microbiota* , Aquaculture*, Iron ; Denitrification
Abstract: Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Salinity-driven nitrogen removal mechanisms in iron-carbon CWs (Fe-C-CWs) remain poorly understood for aquaculture tailwater management. Through a 155-day trial under four salinities (designated as S0, S10, S20, and S30), result showed that S20 achieved optimal removals of total nitrogen (84.9 ± 3.1 %), nitrate (81.8 ± 2.5 %), and ammonium (79.3 ± 3.0 %), significantly outperforming other groups (P < 0.05). Metagenomics revealed that S20 significantly enriched denitrifying taxa (Halothiobacillus, Prolixibacter) and upregulated nitrogen cycling genes (nirB, nrfA, nrfH, hao) and iron cycling genes (feoA, feoB), highlighting the functional synergy between microbial composition and biogeochemical cycling processes. Dual isotope signatures (δ 15 N NO2 / δ 18 O NO2 ) first applied in Fe-C-CWs confirmed salinity-mediated pathway shifts: nitrite oxidation dominated in saline groups, especially in S20 versus reduction in S0. Enzymatic profiling substantiated the concurrent operation of nitrification, denitrification, and anammox pathways across all groups, with activities exhibiting significant salinity-dependent modulation. S20 demonstrated remarkable enzymatic potentiation, where core nitrogen-cycling enzymes including nitrite oxidoreductase (NXR: 8.79 ± 0.67 U/g), nitrate reductase (NAR: 18.13 ± 1.19 U/g), and nitrite reductase (NIR: 6.74 ± 0.47 U/g) showed 16.00∼32.18 % higher than S0 (P < 0.01). This enzymatic synergy suggests salinity-optimized coupling between dissimilatory iron reduction and nitrogen transformation processes. Ecological network analysis revealed significant interactions among microbial phyla, particularly between Proteobacteria and Planctomycetota. This study demonstrates that S20 can enhance interaction between Fe-C matrix and microorganisms, thereby improving the efficiency of Fe-C-CWs in removing nitrogen pollutants from aquaculture tailwater. These findings offer theoretical insights for further understanding the internal operational mechanisms of the Fe-C-CWs.
(Copyright © 2025 Elsevier Ltd. All rights reserved.)
Contributed Indexing: Keywords: Aquaculture tailwater; Iron-carbon CWs (Fe-C-CWs); Metagenomic; Nitrogen removal; Salinity
Substance Nomenclature: N762921K75 (Nitrogen)
E1UOL152H7 (Iron)
Entry Date(s): Date Created: 20250902 Date Completed: 20251021 Latest Revision: 20251021
Update Code: 20251021
DOI: 10.1016/j.watres.2025.124519
PMID: 40897099
Database: MEDLINE
Description
Abstract:Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.<br />Salinity-driven nitrogen removal mechanisms in iron-carbon CWs (Fe-C-CWs) remain poorly understood for aquaculture tailwater management. Through a 155-day trial under four salinities (designated as S0, S10, S20, and S30), result showed that S20 achieved optimal removals of total nitrogen (84.9 ± 3.1 %), nitrate (81.8 ± 2.5 %), and ammonium (79.3 ± 3.0 %), significantly outperforming other groups (P &lt; 0.05). Metagenomics revealed that S20 significantly enriched denitrifying taxa (Halothiobacillus, Prolixibacter) and upregulated nitrogen cycling genes (nirB, nrfA, nrfH, hao) and iron cycling genes (feoA, feoB), highlighting the functional synergy between microbial composition and biogeochemical cycling processes. Dual isotope signatures (δ <sup>15</sup> N <subscript>NO2</subscript> / δ <sup>18</sup> O <subscript>NO2</subscript> ) first applied in Fe-C-CWs confirmed salinity-mediated pathway shifts: nitrite oxidation dominated in saline groups, especially in S20 versus reduction in S0. Enzymatic profiling substantiated the concurrent operation of nitrification, denitrification, and anammox pathways across all groups, with activities exhibiting significant salinity-dependent modulation. S20 demonstrated remarkable enzymatic potentiation, where core nitrogen-cycling enzymes including nitrite oxidoreductase (NXR: 8.79 ± 0.67 U/g), nitrate reductase (NAR: 18.13 ± 1.19 U/g), and nitrite reductase (NIR: 6.74 ± 0.47 U/g) showed 16.00∼32.18 % higher than S0 (P &lt; 0.01). This enzymatic synergy suggests salinity-optimized coupling between dissimilatory iron reduction and nitrogen transformation processes. Ecological network analysis revealed significant interactions among microbial phyla, particularly between Proteobacteria and Planctomycetota. This study demonstrates that S20 can enhance interaction between Fe-C matrix and microorganisms, thereby improving the efficiency of Fe-C-CWs in removing nitrogen pollutants from aquaculture tailwater. These findings offer theoretical insights for further understanding the internal operational mechanisms of the Fe-C-CWs.<br /> (Copyright © 2025 Elsevier Ltd. All rights reserved.)
ISSN:1879-2448
DOI:10.1016/j.watres.2025.124519