Coupled shifts in microbial and mineralogical Fe cycling destabilize organic carbon in converted estuarine wetlands

Coupled shifts in microbial and mineralogical Fe cycling destabilize organic carbon in converted estuarine wetlands | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Coupled shifts in microbial and mineralogical Fe cycling destabilize organic carbon in converted estuarine wetlands Junpeng Li, Qingsong Zeng, Shuling Tang, Yingzi Wu, Yi Zheng, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7067479/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Dec, 2025 Read the published version in Plant and Soil → Version 1 posted 6 You are reading this latest preprint version Abstract Estuarine wetlands are critical organic carbon sinks, where Fe oxides bind with organic carbon to form Fe-bound organic carbon (Fe-OC), which plays an important role in carbon sequestration within these ecosystems. The conversion of natural estuarine wetlands into aquaculture ponds leads to notable changes in both the Fe content and the Fe-OC pool. This study analyzed three typical Chinese estuarine wetlands to investigate changes in Fe fractions and Fe-OC during aquaculture pond conversion, employing 16S rDNA sequencing to examine Fe-related bacterial communities (Fe-oxidizing bacteria and Fe-reducing bacteria) dynamics, thereby revealing interactions between these bacteria, soil Fe, and Fe-OC throughout the transformation process. The results showed that after land-use change, Fe-OC and the molar OC:Fe rations (OC:Fe) in all soil layers decreased significantly by over 54% and 49%, respectively, while the Fe crystalline ratio (the ratio of crystalline Fe oxides to free Fe oxide) increased significantly by more than 100% across all layers. Among the Fe fractions, amorphous Fe oxides (Fe o ), complexed Fe oxides (Fe p ), and Fe-OC were key factors regulating Fe-reducing bacteria ( p < 0.01). In turn, those Fe-related bacteria affected the Fe cycle and the transformation of Fe oxides (mainly Fe o and Fe p ), thereby influencing Fe-OC and OC:Fe. The transformation process leads to Fe reduction, Fe p depletion, and Fe o crystallization, resulting in the loss of Fe-OC. To safeguard the carbon storage function of estuarine wetlands, it is essential to minimize wetland exploitation and implement strategies to curb Fe oxide loss and crystallization, thereby enhancing the stability of these critical carbon pools. Iron Fe-bound organic carbon Fe-oxidizing bacteria Fe-reducing bacteria Aquaculture ponds Estuarine wetlands Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Estuarine wetlands, located at the interface of land, rivers, and oceans, are unique transitional ecosystems with diverse ecological functions. Their high productivity and the low sediment decomposition rates make them important and stable organic carbon sinks (Mei et al., 2024 ; Yan et al., 2023 ). However, rapid population growth in recent times has driven increased demand for seafood, prompting a significant expansion of coastal aquaculture. Studies have shown that from 1985 to 2015, the area of coastal wetlands in China decreased from 10,262 km² to 7,296 km², while the area of aquaculture ponds more than doubled—from 2,305 km² to 4,431 km² (Hu et al., 2023 a; Wang et al., 2021 ). The conversion of estuarine wetlands into aquaculture ponds involves the removal of native vegetation and a marked increase in human disturbance. This transition alters key soil physicochemical properties—such as redox potential, pH, moisture content, and bulk density—and can significantly impact carbon pool stability (Hou et al., 2024 ; Wang et al., 2023 ). For example, studies have shown that soil bulk density increases while porosity declines following such land-use change, reducing soil aeration and water-holding capacity. These changes lead to a significant loss of soil organic carbon content (Lin et al., 2024 ). In addition, the diversity and stability of soil microbial communities tend to decrease after this land use conversion, which may further exacerbate changes in soil properties and carbon loss (Hou et al., 2024 ). In wetland soils, organic carbon can form stable complexes with Fe oxides (Fe-OC) through adsorption or co-precipitation, making the organic carbon difficult for microbial decomposition. This binding mechanism significantly enhances the long-term storage of organic carbon (Han et al., 2024 ; Wang et al., 2022a ). The redox cycling of Fe is a key process regulating Fe-bound organic carbon, with Fe-related bacteria (including Fe-oxidizing and Fe-reducing bacteria) playing critical roles. Under anaerobic conditions, Fe-reducing bacteria (FeRB) reduce Fe(Ⅲ) to Fe(Ⅱ), releasing organic carbon bound to Fe oxides and promoting organic carbon degradation (Kügler et al., 2019 ). Conversely, in oxidative environments, Fe-oxidizing bacteria (FeOB) oxidize Fe(Ⅱ), facilitating the reformation of Fe-OC complexes (Emerson et al., 2015 ; Wang et al., 2024 ). The oxidation states of Fe in soil mainly include free Fe oxides (Fe d ), amorphous Fe oxides (Fe o ), and complexed Fe oxides (Fe p ). Among these, Fe d is highly stable and functions as a key mineral cementing agent, but its low specific surface area limits its ability to adsorb organic carbon. In contrast, Fe o has a much larger surface area and higher reactivity, providing strong adsorption capacity and making it more effective at stabilizing organic carbon. Fe p refers to iron bound to organic matter (e.g., humus) or inorganic soil components, where organic ligands mediate Fe–organic carbon bridging through coordination bonds, thereby enhancing the stability of organic carbon (Azadi et al., 2021 ; Rezapour et al., 2010 ; Xue et al., 2019 ). However, the mechanisms by which Fe-related bacteria regulate different Fe oxide forms and influence Fe-organic carbon binding remains poorly understood. Due to the unique tidal effects, estuarine wetlands experience frequent changes in soil redox conditions, which promote the Fe redox cycling process and enable the stable existence of Fe-bound organic carbon (Hu et al., 2023 ). However, converting such natural wetlands into aquaculture ponds disrupts the original redox conditions and Fe cycling processes of estuarine wetlands, thereby affecting the interaction between Fe and organic carbon. The study of Fe-OC has recently gained attention as a key indicator of carbon pool stability in natural wetlands (Bi et al., 2024 ; Lin et al., 2023 ; X. Liu et al., 2023 ). For example, research on Phragmites australis wetlands in the Yangtze River estuary revealed that the Fe-OC accumulation increased significantly under the flooding and high salinity stress (Bi et al., 2024 ). Microbial activity has also been identified as a major contributor to Fe-OC formation (Liu et al., 2023 ). In freshwater wetlands, vegetation type has been shown to influence the accumulation of Fe-bound organic carbon (Chen et al., 2024 ). However, limited studies have explored the transformation of Fe-OC and its driving factors during the transformation of natural wetlands to aquaculture ponds. In this study, we investigated typical estuarine wetlands in China to examine the changes in Fe content, Fe-OC and Fe-related bacterial communities across three different vegetation types, namely, Phragmites australis , Aegiceras corniculatum , Kandelia candel . These changes were assessed during the transition from oxidized, looser soils to reduced, compacted soils following the conversion of natural wetlands into aquaculture ponds. The aim was to clarify the interactions among Fe-related bacteria, various types of Fe, and Fe-OC throughout this transformation process. By identifying how land use change influences Fe-OC dynamics and the key driving factors, this study provides insights into strategies for enhancing the stability of carbon pools in estuarine wetlands. 2. Materials and Methods 2.1. Study Area and Soil Sampling This study was conducted in three estuarine natural wetlands (NW) and their reclaimed aquaculture ponds (AP) located in the Min River Estuary (MJ), Zhang River Estuary (ZJ), and Jiu Long River Estuary (JL) in Fujian, China (Fig. 1 ). Detailed information on each sampling site is shown in Table S1 . All sampling sites are located within subtropical monsoon climate zone. The Min River Estuary area has an average annual temperature of 19.6 ℃ and average annual precipitation of 1346 mm; the Zhang River Estuary area has an average annual temperature of 21.0 ℃ and average annual precipitation of 1371 mm; the Jiu Long River Estuary area has an average annual temperature of 21.2 ℃ and average annual precipitation of 1714.5 mm. From October to December 2021, five plots (10 m × 10 m square) were randomly selected at each site and for each environmental type. Within each plot, one sub-plot (1 m × 0.6 m) was chosen, and soil samples were collected from the upper layer (0–15 cm) and lower layer (15–30 cm) using a soil sampler with a diameter of 9 cm. A total of 60 samples were collected (3 sampling sites × 2 environment types × 2 soil layers × 5 replicates). Samples were immediately stored in sterile bags under refrigerated conditions and transported back to the laboratory. In the laboratory, soil samples were homogenized, and stones and plant roots were removed using a 2 mm sieve. Each soil sample was divided into two parts: one part was air-dried and ground through a 0.15 mm sieve for determination of soil Fe fractions and Fe-OC content; the other part was stored as moist soil at -20℃ for analysis of soil Fe-oxidizing bacteria (FeOB) and Fe-reducing bacteria (FeRB) communities. 2.2. Determination of Fe in the soil by valence and by form The valence state Fe in soil samples was extracted using 0.5 mol·L − 1 HCl. The samples were divided into two parts: one part was used to determine Fe(Ⅱ), and the other part was used to determine the total Fe extracted by hydrochloric acid (HCl-Fe t ). The Fe(Ⅲ) content was calculated as the difference between Fe(Ⅱ) and HCl-Fe t (Liu et al., 2019 ). Free Fe oxides in the soil (Fe d ) were obtained by the DCB (Dithionite-Citrate-Bicarbonate) reduction dissolution method. Amorphous Fe oxides (Fe o ) were extracted using 0.2 mol·L − 1 ammonium oxalate buffer solution (pH ≈ 3.2). Complexed Fe oxides in the soil (Fe p ) were extracted using 0.1 mol·L − 1 sodium pyrophosphate solution (pH = 8.5) (Yao et al., 2023 ). The Fe content in all extracted forms was determined as follows: an appropriate amount of extract was taken, and except for the extract used to determine Fe(Ⅱ), a certain amount of hydroxylamine hydrochloride was added to the other extracts to reduce Fe to divalent Fe. After sufficient reaction, a certain amount of sodium acetate and o-phenanthroline solution was added for color development. The optical density (OD) value was measured at 510 nm wavelength using a UV spectrophotometer. The content of each valence state and form of Fe was then calculated based on the sample OD value and standard sample OD value curve (Lin et al., 2023 ). The formulas for calculating the Fe activation index (Fe-AI), Fe complexing index (Fe-CI), and Fe crystalline ratio (Fe-CR) are as follows (Jia et al., 2024 ; Zheng et al., 2016 ): $$\:Fe\:activation\:index\:\left(\%\right)\:=\:({Fe}_{o}\:/\:{Fe}_{d})\:\times\:\:100\%\:$$ $$\:Fe\:complexing\:index\:\left(\%\right)\:=\:({Fe}_{p}\:/\:{Fe}_{d})\:\times\:\:100\%$$ $$\:Fe\:crystalline\:ratio\:=\:({Fe}_{d}\:-\:{Fe}_{o})\:/\:{Fe}_{o}$$ Fe-bound organic carbon in soil (Fe-OC) was determined by the organic carbon-bound precipitate generated during the DCB method extraction of free Fe oxides. However, as some water-soluble organic carbon may be produced during extraction, a control experiment is required for adjusting. In this experiment, a 1.6 mol·L − 1 NaCl solution was used to replace sodium citrate in the DCB method to treat soil samples. The total organic carbon content in the precipitates obtained from both treatments was then measured using a Vario EL III carbon-nitrogen element analyzer (Lin et al., 2023 ). The calculation formulas for Fe-bound organic carbon (Fe-OC), the proportion of Fe-bound organic carbon in organic carbon ( f Fe−OC ), and the molar OC:Fe rations (OC:Fe) are as follows (Tian and Lu, 2023 ): $$\:Fe-OC\:(g/kg)\:={\:OC}_{NaCl}\:-\:{OC}_{DCB}$$ $$\:{f}_{Fe-OC\:}\left(\%\right)\:=\:Fe-OC\:/\:SOC\:\times\:\:100\%$$ $$\:OC/Fe\:=\:(Fe-OC\:\times\:\:{M}_{Fe})\:/\:({M}_{C}\:\times\:\:{m}_{{Fe}_{d}})$$ OC NaCl : Organic carbon content in the precipitate after NaCl solution treatment; OC DCB : Organic carbon content in the precipitate after DCB method treatment; M C : Molar mass of carbon atoms; M Fe : Molar mass of Fe atoms; m Fed : Content of free Fe oxides. 2.3. Determination of soil microorganisms Soil DNA was extracted from wetland soil samples using the CTAB(Cetyltrimethylammonium Bromide) method. The purity and concentration of extracted DNA were assessed via agarose gel electrophoresis. Subsequently, an appropriate volume of genomic DNA was diluted to 1 ng·µL⁻¹ using sterile ultrapure water. The diluted DNA served as template for PCR amplification, targeted at the V3-V4 region of 16S rRNA using 341F (CCTAYGGGRBGCASCAG) and 806R (GGACTACNNGGGGTATCTAAT) as primers (Hossen et al., 2025 ; Maretto et al., 2022 ). The PCR products were analyzed by agarose gel electrophoresis at 2% for 40 min. Aliquots were mixed according to the concentration of the PCR products, and the products were purified by agarose gel electrophoresis using 1×TAE at 2% concentration to cut and recover the target bands. The PCR product purification kit used in this process was Thermo Scientific GeneJET gel recovery kit. The library was constructed using the Ion Plus Fragment Library Kit 48rxns from Thermofisher, the constructed library was quantified by Qubit, and after the library was tested and qualified, it was sequenced using the Life Ion S5TM from Thermofisher platform(Inc., USA). 2.4. Data Analysis The data on Fe-related bacteria were based on the classification results of soil bacterial communities and the taxonomic names of Fe-related bacteria from known literature databases (Peng et al., 2019 ). Standard errors of Fe contents, Fe-OC related indicators, and alpha diversity indices of Fe-related bacteria were calculated using Excel2019. Origin2024 was used for one-way ANOVA on various Fe contents, Fe oxides characteristic parameters, Fe-OC related indicators, and alpha diversity indices of Fe-related bacteria to compare content changes among different environmental types within the same site and soil layer, and to create charts. Two-way ANOVA in the same software was used to compare differences in soil layer data influenced by site, environmental type, and their interaction (site × environmental type). The ‘GGally’ package was used to analyze correlations among various Fe contents, Fe oxides characteristic parameters, and Fe-OC related indicators in R4.3.2. The ‘vegan’ package was used for PCoA analysis of Fe-related bacterial communities, and Adonis was used to compare differences in Fe-related bacterial communities in soils of different environmental types at the same site. The package was also used for redundancy analysis of Fe-related bacteria and environmental factors to determine the influencing factors of Fe-related bacteria. The ‘plspm’ package was used for PLS-SEM analysis of Fe-related bacterial communities, various Fe contents, OC:Fe, and Fe-OC, with Fe-related bacterial communities characterized by Shannon and Chao1 indices. The model was initially established based on previous studies and further optimized according to calculation results. 3. Results 3.1. Fe content and characteristic parameters of soil types before and after conversion of estuarine wetlands to aquaculture ponds Among the three types of estuarine natural wetland soils, the contents of Fe(Ⅱ) and Fe p in Kandelia candel wetlands were significantly higher than those in Phragmites australis and Aegiceras corniculatum wetlands (Table 1 ). After conversion to aquaculture ponds, Fe(Ⅱ) content increased by more than 65% relative to natural wetlands in all soil layers, while Fe(Ⅲ) content decreased by more than 18% ( p < 0.05). A pronounced decline was observed in Fe oxides ( p < 0.05). In the upper soil layer, Fe d content decreased from 19.63 ± 0.36 to 17.58 ± 0.53 g·kg − 1 . Meanwhile, Fe d in the lower soil layer declined from 19.35 ± 0.48 to 17.25 ± 0.44 g·kg − 1 . Fe o and Fe p showed more significant decreases compared to natural wetlands ( p < 0.05). In the upper soil layer, Fe o content declined by 32.15%, and Fe p by 51.96%. In the lower layer, Fe o decreased by 29.98%, with Fe p reduction reaching 27.73%. Two-way ANOVA results (Table S2) indicated that in the upper soil layer, site​ significantly affected Fe(Ⅱ)、Fe(Ⅲ)、Fe(Ⅲ)/ Fe(Ⅱ)、Fe o 、Fe p ( p < 0.05), while environment type significantly affected Fe(Ⅱ), Fe(Ⅲ), Fe d , Fe o , and Fe p ( p < 0.01). The interaction between environment type and site significantly influenced Fe(Ⅱ), Fe(Ⅲ)/Fe(Ⅱ), Fe d , Fe o , and Fe p ( p < 0.05). In the lower soil layer, site​ significantly affected Fe(Ⅱ)、Fe(Ⅲ)、Fe(Ⅲ)/ Fe(Ⅱ)、Fe o 、Fe p ( p < 0.05), while environment type significantly affected Fe(Ⅱ), Fe(Ⅲ), HCl-Fet, Fe(Ⅲ)/Fe(Ⅱ), Fe d , Fe o, and Fe p ( p < 0.05). The interaction between environment type and site significantly impacted Fe(Ⅱ), Fe(Ⅲ)/Fe(Ⅱ), Fe o , and Fe p ( p < 0.05).Fe(Ⅱ), Fe(Ⅲ)/Fe(II), Fe o , and Fe p ( p < 0.05). Table 1 Fe content of various types before and after the transformation of estuarine wetlands into aquaculture ponds in different regions. MJ, Minjiang Estuary; JL, Jiulong Estuary; Zhangjiang Estuary; Total, overall of each sampling point; PAW, Phragmites australis Wetland; ACW, Aegiceras corniculatum Wetland; KCW, Kandelia candel Wetland; NW, natural wetland; AP, aquaculture pond; Fe(Ⅱ), divalent Fe, g·kg − 1 ; Fe(Ⅲ), trivalent Fe, g·kg − 1 ; HCl-Fe t , total Fe extracted by hydrochloric acid, g·kg − 1 ; Fe(Ⅲ)/Fe(Ⅱ), ratio of trivalent Fe to divalent Fe content; Fe d , free Fe oxides, g·kg − 1 ; Fe o , amorphous Fe oxides, g·kg − 1 ; Fe p , complexed Fe oxides, g·kg − 1 . Data are presented as mean ± SE, uppercase letters indicate significant differences ( p < 0.05) for the same soil layer across different sites within natural wetlands or aquaculture ponds, lowercase letters indicate significant differences ( p < 0.05) between natural wetlands and aquaculture ponds for the same soil layer and site. Site Soil layer Environmental type Fe(Ⅱ) Fe(Ⅲ) HCl- Fe t Fe(Ⅲ)/ Fe(Ⅱ) Fe d Fe o Fe p MJ 0–15 PAW 1.28 ± 0.11 Aa 12.83 ± 1.01 Aa 14.11 ± 0.95 Aa 10.66 ± 1.98 Aa 18.06 ± 0.36 Aa 9.25 ± 0.29 Aa 0.269 ± 0.008 Aa AP 1.16 ± 0.04 Aa 12.93 ± 0.99 Aa 13.81 ± 0.80 Aa 21.19 ± 6.70 Aa 18.37 ± 1.23 Ab 10.02 ± 0.39 Ab 0.256 ± 0.004 Aa 15–30 PAW 0.88 ± 0.22 Aa 12.67 ± 1.09 Aa 13.83 ± 1.10 Aa 10.89 ± 0.89 Aa 19.68 ± 0.54 Aa 7.92 ± 0.25 ABa 0.287 ± 0.004 Aa AP 1.29 ± 0.19 Ab 9.06 ± 0.92 Ab 10.35 ± 1.08 Ab 7.40 ± 0.85 ABa 17.87 ± 0.64 Aa 9.86 ± 0.31 Aa 0.293 ± 0.008 Aa JL 0–15 ACW 0.69 ± 0.05 Ba 12.26 ± 0.55 Aa 12.94 ± 0.59 Aa 18.1 ± 0.88 Aa 20.47 ± 0.25 Ba 9.65 ± 0.46 ABa 0.432 ± 0.013 Ba AP 0.36 ± 0.07 Bb 10.49 ± 1.10 Bb 11.32 ± 1.07 Bb 12.93 ± 1.69 Ba 19.70 ± 0.61 Bb 9.43 ± 0.52 Bb 0.448 ± 0.024 Ab 15–30 ACW 0.83 ± 0.05 Aa 9.65 ± 0.49 ABa 10.01 ± 0.47 ABa 32.43 ± 8.00 ABa 15.51 ± 0.64 Aa 3.39 ± 0.25 Ba 0.241 ± 0.012 Ba AP 0.56 ± 0.04 Bb 8.46 ± 0.35 Aa 9.02 ± 0.37 Aa 15.34 ± 1.08 Aa 16.06 ± 0.36 Ab 3.30 ± 0.49 Bb 0.244 ± 0.015 Cb ZJ 0–15 KCW 1.42 ± 0.05 Aa 12.32 ± 1.01 Aa 13.75 ± 1.00 Aa 8.72 ± 0.86 Aa 20.37 ± 0.49 Ba 10.69 ± 0.81 Ba 1.447 ± 0.127 Ca AP 4.11 ± 0.39 Cb 8.92 ± 0.40 Bb 10.52 ± 0.31 ABa 5.90 ± 0.86 Ab 19.98 ± 0.40 Cb 10.98 ± 0.81 Aa 0.725 ± 0.019 Bb 15–30 KCW 1.61 ± 0.18 Ba 8.00 ± 1.34 Ba 12.11 ± 1.39 Ba 2.03 ± 0.41 Ba 17.54 ± 0.27 Aa 8.76 ± 0.23 Aa 0.503 ± 0.021 Ca AP 3.63 ± 0.43 Cb 7.47 ± 1.09 Aa 11.11 ± 1.43 Aa 2.07 ± 0.19 Ba 17.81 ± 1.00 Aa 8.48 ± 0.08 Ab 0.494 ± 0.007 Bb Total 0–15 NW 1.13 ± 0.09 a 12.47 ± 0.48 a 13.60 ± 0.48 a 12.49 ± 1.30 a 19.63 ± 0.36 a 9.86 ± 0.34 a 0.716 ± 0.145 a AP 1.87 ± 0.45 a 10.11 ± 0.76 b 11.98 ± 0.70 a 15.12 ± 4.22 a 17.58 ± 0.53 b 6.69 ± 0.64 b 0.344 ± 0.031 b 15–30 NW 1.10 ± 0.13 a 10.78 ± 0.65 a 11.88 ± 0.57 a 13.34 ± 2.72 a 19.35 ± 0.48 a 10.14 ± 0.36 a 0.476 ± 0.052 a AP 1.83 ± 0.38 a 8.33 ± 0.48 b 10.16 ± 0.61 b 8.27 ± 1.52 a 17.25 ± 0.44 b 7.21 ± 0.78 b 0.344 ± 0.029 b After the estuarine natural wetlands were converted into aquaculture ponds, in the upper soil layer, Fe activation index showed a ​25.60% reduction relative to the baseline of natural wetlands​ (Fig. 2 a). Fe complexing index showed a ​45.40% reduction relative to the baseline of natural wetlands (Fig. 2 b). Fe crystalline ratio showed a ​103.96% increase relative to the baseline of natural wetlands (Fig. 2 c). In the lower soil layer, Fe activation index showed a ​21.59% reduction relative to the baseline of natural wetlands (Fig. 2 d). Fe complexing index showed a ​28.44% reduction relative to the baseline of natural wetlands (Fig. 2 e). Fe crystalline ratio showed a ​117.02% increase relative to the baseline of natural wetlands (Fig. 2 f) ( p < 0.05). 3.2. Characteristics of soil Fe-OC before and after estuarine wetlands are converted into aquaculture ponds In various estuarine natural wetlands, the Fe-OC content and OC:Fe in Kandelia candel wetland soils were significantly higher than those in Phragmites australis wetlands and Aegiceras corniculatum Wetlands ( p < 0.05) (Fig. 3 , Fig. 5 ). After conversion to aquaculture ponds, the ​upper soil layer​ Fe-OC content relatively decreased by 54.30% (Fig. 3 a), with OC:Fe declining from 0.61 to 0.31 (Fig. 5 a). These changes were significantly influenced by site, environmental type, and their interaction ( p < 0.05). In the ​lower soil layer​ Fe-OC content relatively decreased by 64.62% (Fig. 3 b), with OC:Fe dropping from 0.65 to 0.26 (Fig. 5 b) ( p < 0.05), significantly affected by site and environmental type ( p < 0.05). Additionally, the f Fe−OC proportion increased after wetland conversion, with site showing a significant effect in the lower layer (Fig. 2 ). 3.3. Correlation characteristics of soil Fe-OC and Fe before and after estuarine wetlands are converted into aquaculture ponds In the overall process of estuarine wetland transformation into aquaculture ponds (Fig. 6 ), Fe-OC is significantly positively correlated with OC:Fe, Fe d , Fe o , Fe p , Fe-AI, and Fe-CI ( p < 0.001), and significantly negatively correlated with Fe-CR ( p < 0.01). OC:Fe is significantly positively correlated with Fe d , Fe o , Fe p , Fe-AI, and Fe-CI ( p < 0.01), and significantly negatively correlated with Fe-CR ( p < 0.01). Fe(Ⅱ) is significantly positively correlated with Fe-AI ( p < 0.05) and significantly negatively correlated with Fe-CR ( p < 0.01). Fe(Ⅲ) is significantly positively correlated with Fe d ( p < 0.01). Meanwhile, before land use change (Fig. 6 ), Fe-OC is only significantly positively correlated with Fe o ( p < 0.001), but after transformation into aquaculture ponds (Fig. 6 ), Fe-OC is significantly positively correlated with Fe o , Fe p , Fe-AI, and Fe-CI ( p < 0.05), and significantly negatively correlated with Fe-CR ( p < 0.01). 3.4. Differences in the diversity of soil Fe-related bacteria communities before and after estuarine wetlands are converted into aquaculture ponds Conversion of Phragmites australis wetlands to aquaculture ponds significantly reduced soil FeRB diversity indices (Sobs, Shannon, Chao1), while increasing FeOB indices (Sobs, Shannon, Chao1) ( p < 0.05) (Table 2 ). For Aegiceras corniculatum wetland conversion, both FeRB and FeOB exhibited significant decreases in Sobs, Shannon, ACE, and Chao1 indices ( p < 0.05). For Kandelia candel wetlands conversion, FeRB showed reductions in Sobs and Shannon indices (p < 0.05) (Table 2 ). Table 2 Alpha diversity index of soil Fe-related bacteria. Lowercase letters indicate significant differences ( p < 0.05) between natural wetlands and aquaculture ponds for the same soil layer and site. Fe-related bacteria Sampling point Sobs Shannon ACE Chao1 Coverage(%) FeRB MJPAW 125.40 ± 5.12 a 4.04 ± 0.05 a 185.07 ± 14.12 a 179.40 ± 10.31 a 94.97 ± 0.01 MJAP 107.00 ± 4.64 b 3.40 ± 0.19 b 181.30 ± 14.31 a 151.07 ± 6.16 b 95.34 ± 0.01 JLACW 118.80 ± 3.28 a 3.64 ± 0.09 a 164.71 ± 4.40 a 162.12 ± 8.97 a 95.15 ± 0.19 JLAP 77.40 ± 9.54 b 2.85 ± 0.31 b 148.64 ± 20.94 b 116.60 ± 13.27 b 96.45 ± 0.31 ZJKCW 112.80 ± 3.08 b 3.55 ± 0.07 b 182.42 ± 18.38 a 174.27 ± 16.16 a 94.90 ± 0.35 ZJAP 145.00 ± 2.77 a 4.10 ± 0.10 a 216.52 ± 12.49 a 197.65 ± 8.39 a 93.97 ± 0.29 FeOB MJPAW 183.20 ± 5.30 b 4.30 ± 0.07 a 255.14 ± 12.77 b 245.47 ± 5.53 b 96.16 ± 0.14 MJAP 220.00 ± 4.59 a 4.40 ± 0.02 a 336.71 ± 25.60 a 306.70 ± 16.46 a 94.88 ± 0.27 JLACW 191.40 ± 12.16 a 4.03 ± 0.13 a 322.02 ± 34.10 a 292.12 ± 20.84 a 95.09 ± 0.37 JLAP 122.20 ± 22.05 b 3.28 ± 0.32 b 204.63 ± 32.84 b 171.01 ± 31.61 b 97.06 ± 0.51 ZJKCW 186.40 ± 4.21 a 4.17 ± 0.05 a 290.43 ± 19.14 a 279.72 ± 12.47 a 95.69 ± 0.20 ZJAP 193.40 ± 5.84 a 4.40 ± 0.04 a 286.21 ± 19.57 a 262.51 ± 10.34 a 95.76 ± 0.20 Through PCoA analysis of soil FeRB community differences in estuarine natural wetlands before and after conversion to aquaculture ponds (Fig. 7a, R 2 = 0.714, p < 0.001). The PCoA1 and PCoA2 axes explained 31.72% and 17.84% of the total variation, respectively. Further Adonis analysis indicated significant differences in soil FeRB among various types of estuarine natural wetlands before and after conversion to aquaculture ponds ( p < 0.01) (Table S3). Similarly, PCoA analysis of soil FeOB community differences in estuarine natural wetlands before and after conversion to aquaculture ponds (Fig. 7b, R 2 = 0.712, p < 0.001). The PCoA1 and PCoA2 axes explained 28.86% and 19.96% of the total variation, respectively. Further Adonis analysis demonstrated significant differences in soil FeOB among various types of estuarine natural wetlands before and after conversion to aquaculture ponds ( p < 0.01) (Table S3). 3.5. Differences in family-level community structure of soil Fe-related bacteria before and after estuarine wetlands are converted into aquaculture ponds After various types of estuarine natural wetlands are converted into aquaculture ponds, the dominant types and relative abundances of FeRB families undergo certain changes (Fig. 8 a). The dominant bacterial family in Phragmites australis wetlands is Desulfobacteraceae, whose relative abundance decreases from 26.7–18.6% after conversion to aquaculture ponds, resulting in Thiobacillaceae becoming the dominant family in the soil of the converted aquaculture ponds, with its relative abundance increasing from 2.6–23.0%. The dominant bacterial family in Aegiceras corniculatum wetlands is Desulfobacteraceae, whose relative abundance decreases from 48.7–33.1% after conversion to aquaculture ponds. The dominant bacterial family in Kandelia candel Wetland is Desulfobulbaceae, whose relative abundance decreases from 37.9–6.7% after conversion, leading to Anaeromyxobacteraceae becoming the dominant family in the soil of the converted aquaculture ponds, with its relative abundance increasing from less than 0.1–41.5%. The relative abundance of dominant FeOB families remains relatively stable after the conversion of various types of estuarine natural wetlands into aquaculture ponds (Fig. 8 b). 3.5. The influence relationship between soil Fe-related bacterial communities, Fe, and Fe-OC Redundancy analysis (RDA) explained 39.47% and 5.05% of the variability in the FeRB community, respectively (Fig. 9 a). Fe p ( R 2 = 0.579, p < 0.01), Fe o ( R 2 = 0.578, p < 0.01), and Fe-OC ( R 2 = 0.485, p < 0.01) are the main factors influencing the FeRB community. Redundancy analysis (RDA) also explained 19.83% and 3.60% of the variability in the FeOB community, respectively (Fig. 9 b). Fe p ( R 2 = 0.162, p > 0.05) and Fe(Ⅱ) ( R 2 = 0.123, p > 0.05) are the main factors influencing the FeOB community. The PLS-SEM analysis of the Fe-related bacterial community, Fe, and Fe-OC (Fig. 9 c) further showed that the FeRB community positively influenced Fe o ( p < 0.001) and Fe(Ⅱ) ( p < 0.001). In turn, Fe(Ⅱ) negatively influenced Fe(Ⅲ) ( p < 0.01), allowing Fe(Ⅲ) to positively influence Fe d ( p < 0.001). The FeOB community also had a positive effect on Fe d ( p < 0.01), with Fe d subsequently positively influencing Fe o ( p < 0.001). Fe o further exerted a positive influence on Fe p ( p < 0.001), which Fe p ultimately had a direct impact on Fe-OC ( p < 0.05) and an indirectly effect on Fe-OC ( p < 0.001) through its influence on OC:Fe ( p < 0.01). 4. Discussion 4.1. Impact of estuarine Wetland Conversion to Aquaculture Ponds on Fe Dynamics The key to soil Fe cycling lies in the interconversion between Fe(Ⅱ) and Fe(Ⅲ). When natural wetlands are converted into aquaculture ponds, changes in soil properties such as soil moisture content, pH, and aeration conditions change, lead to corresponding shifts in the content of Fe(Ⅱ) and Fe(Ⅲ) (Wang et al., 2022b ). In this study, we observed an overall increase in Fe(Ⅱ) and a decrease in Fe(Ⅲ) content following the conversion of natural wetlands to aquaculture ponds. The soils of aquaculture ponds are often subjected to prolonged anaerobic conditions and contain reducing sediments rich in electron donors, which can substantially enhance the reduction of Fe(Ⅲ) to Fe(Ⅱ) (Tan et al., 2022 ). However, some sampling sites showed different trends from the overall pattern after the conversion of natural wetlands. Specifically, in the Phragmites australis wetland at the Minjiang Estuary and the Aegiceras corniculatum Wetland at the Jiulong River Estuary, Fe(Ⅱ) content exhibited an opposite pattern. This may be due to differences in radial oxygen loss (ROL) from the roots of different wetland vegetation types (Pi et al., 2009 ; Cheng et al., 2015 ). The adsorption and utilization of Fe(Ⅱ) by plants mainly come from the iron films on their surfaces, which are primarily composed of Fe oxides (St-Cyr and Crowder, 1989 ). In natural wetlands, plants with weaker root ROL introduced more anaerobic microsites in the rhizosphere, leading to increased Fe(Ⅱ) content and promoting the formation of thicker iron films on the plant surfaces (Chen et al., 2008 ; Neubauer et al., 2007 ). After conversion to aquaculture ponds, although the redox conditions of such vegetated wetland soils do not significantly decrease, the absence of plants disrupts the plant-mediated Fe cycling, ultimately leading to reduced Fe(Ⅱ) content. After natural wetlands are reclaimed to aquaculture ponds, soil properties change from periodic drainage to long-term flooding, resulting in a decrease in soil redox potential ( Hu et al., 2023 b) and an increase in reductive sediments. Studies have shown that Fe p can bind with soil humic substances, promoting the formation of Fe-OC complexes (Huang et al., 2021 ; Huang et al., 2017 ). Correlation analysis in this study also showed a significant positive correlation between Fe p and Fe-OC ( p < 0.001). Therefore, the observed decline in Fe p after wetland conversion is likely attributable to a concurrent reduction in soil organic matter which limits the availability of organic ligands necessary for complexation(Lin et al., 2024 ). In addition, the decrease in redox potential also promotes the preferential reduction of Fe o , which are structurally less stable and more soluble (Thompson et al., 2006 ). Consequently, after the conversion of natural wetlands to aquaculture ponds, the Fe activation index of Fe oxides decreases ( p < 0.05), the Fe crystalline ratio increases ( p < 0.05), and the Fe complexing index decreases. Due to site-specific differences in soil physicochemical properties and vegetation traits, the extent and direction of Fe redox transformations vary after land use change, ultimately resulting in differences in the changes of various Fe oxides (Neubauer et al., 2007 ; Saaltink et al., 2017 ). 4.2. The impact of wetland conversion to aquaculture ponds on Fe-OC Correlation analysis in the study indicates that soil Fe-OC is mainly positively regulated by factors such as Fe d , Fe o , Fe p , Fe activation index, and Fe complexing index, and negatively regulated by Fe crystalline ratio. Periodic flooding in natural wetlands causes frequent redox changes of soil Fe, and abundant plants and litter provide a large amount of organic carbon sources, creating favorable conditions for the formation of Fe-OC (Chi et al., 2021 ; Wissing et al., 2014 ). However, after conversion to aquaculture ponds, the reductive conditions become excessively rich ( Hu et al., 2023 b), leading to a lack of electron acceptors in the soil, an increase in reduced Fe content, a significant decrease in various Fe oxides, and a corresponding significant reduction in Fe-OC ( p < 0.05). Studies show that soil Fe(Ⅱ) can undergo isotope exchange with Fe(Ⅲ) on the surface of Fe oxides, promoting structural rearrangement within Fe oxides, causing Fe o to transform into crystalline Fe oxides (Liu et al., 2021 ; Pizarro et al., 2017 ). Crystalline Fe oxides indicate a lack of active sites and are less likely to bind with organic carbon compared to Fe o (Tian and Lu, 2023 ). Additionally, under anaerobic conditions, Fe o are easily reduced, leading to the release of Fe-OC contained within (Wang et al., 2024 ), thereby exacerbating the loss of Fe-OC after soil use change. Under oxidizing conditions, Fe-OC formed by Fe o through physical adsorption or chemical bonding is more stable, but this Fe-OC is prone to dissolution and loss under reducing conditions (Wang et al., 2024 ). Under reducing conditions, Fe-OC formed by Fe p and organic carbon through coordination bonds or hydrogen bonds is more stable (Herndon et al., 2017 ), which is consistent with the correlation analysis results in this study. When the soil is converted to more strongly reducing aquaculture ponds, a significant correlation between Fe-OC, Fe p , and Fe complexing index is observed. When the soil OC:Fe ratio is less than 1, Fe oxides mainly combines with organic carbon through adsorption. When the OC:Fe ratio is greater than 6, the two mainly combine through co-precipitation (Wang et al., 2017 ). Therefore, in natural wetlands and aquaculture pond soils, Fe oxides mostly combines with organic carbon through adsorption. As a result, after land use changes, Fe-OC in various wetland soils generally experiences significant loss, with the most obvious loss occurring in Kandelia candel Wetlands (loss in the lower soil layer reaching 187.95%). This phenomenon primarily arises because Kandelia obovata exhibits higher ROL from its roots, leading to sufficient oxidizing conditions in wetland soils, where Fe-OC formation is predominantly based on Fe o . After conversion to aquaculture ponds, the soil shifts to a strongly reduced state, favoring Fe p as the primary component of Fe-OC. However, land-use conversion results in significant loss of soil organic matter (Herndon et al., 2017 ; Lin et al., 2024 ), causing a concomitant decline in Fe p content, which is tightly bound to humic acids and other organic substances. Among various wetlands, the reduction in Fe p is most pronounced in Kandelia obovata wetlands converted to aquaculture ponds, particularly in the ​upper soil layer​.When natural wetlands are converted into aquaculture ponds, a large amount of organic carbon is lost, but the change in Fe oxides content is more stable compared to the loss of organic carbon (Sun et al., 2023 ). Under these conditions, the OC:Fe significantly decreases ( p < 0.05), and the proportion of Fe-OC in total organic carbon does not significantly decline. In addition, the reduction in redox potential leads to the reduction of Fe oxides, causing the loss of Fe o , which has more sites binding organic carbon, thereby exacerbating the decreasing trend of OC:Fe (Pizarro et al., 2017 ; Wang et al., 2024 ). 4.3. Effect of Fe-related bacteria communities on Fe-OC and suggestions for carbon restoration Fe-related bacteria are a group of microorganisms that are extremely sensitive to soil redox potential. After natural wetlands are converted into aquaculture ponds, the decrease in redox potential leads to significant changes in the Fe-related bacteria community (Yang et al., 2021 ), which is consistent with the results in this study. However, the process of converting natural wetlands into aquaculture ponds not only involves a decrease in redox potential, but also related to the changes in soil physicochemical properties, such as pH and moisture content (Lin et al., 2024 ). Studies have shown that soils with lower pH are more conducive to the growth of FeRB (Högfors-Rönnholm et al., 2020 ), and soils with high moisture content also promote the growth of FeRB due to their sufficient reducing conditions, (Zecchin et al., 2017 ). Compared to the Kandelia candel Wetland, the Phragmites australis wetland and the Aegiceras corniculatum wetland experienced a greater reduction in soil acidity and a significant decrease in moisture content after conversion to aquaculture ponds, which lead to a trend of decreased FeRB community diversity after conversion. In natural wetlands, radial oxygen loss (ROL) from plant roots results in less Fe(Ⅱ) in the soil (Sánchez-Olivares et al., 2019 ), and FeOB have low diversity due to a lack of electron donors. After conversion to aquaculture ponds, Fe(Ⅱ) significantly increased, which might be the reason of the increase of soil FeOB diversity. However, the root structure of Aegiceras corniculatum is simpler compared to Phragmites australis and Kandelia candel , with weaker root ROL (Cheng et al., 2015 ) and more Fe(Ⅱ). After conversion to aquaculture ponds, soil oxidation decreases while Fe(Ⅱ) decreased, leading to a significant decline in FeOB community diversity in the Aegiceras corniculatum wetland. Fe p and Fe o are important components in the formation of Fe-OC. In anaerobic environments, Fe p , as a key source of Fe(Ⅲ), directly contacts the reducing substances secreted by FeRB, leading to its reduction to Fe(Ⅱ) (Herndon et al., 2017 ; Ortiz-Castillo et al., 2021 ). Due to its high specific surface area and solubility on the surface, Fe o serves as an ideal electron acceptor for FeRB (Martinez et al., 2003 ). During the reduction of Fe p and Fe o , Fe-OC would be released (Wang et al., 2024 ), which leads to FeRB being mainly regulated by Fe o , Fe p , and Fe-OC ( p < 0.01). Fe p often binds with organic matter, and this binding form promotes Fe dissolution, thereby providing more Fe(Ⅱ) substrates for FeOB. The content of Fe(Ⅱ) substrates is a key factor regulating FeOB (Riedel et al., 2013 ), and the results of this study partially confirm this point. The mutual adaptation between Fe-related bacterial communities and Fe environments plays a critical role in maintaining the stability of carbon pools in estuarine natural wetlands (Dubinsky et al., 2010 ). However, after conversion to aquaculture ponds, prolonged anaerobic soil conditions, substantial loss of SOC, and the absence of vegetation roots leading to soil compaction further exacerbate the reduced state of the soil. These changes are accompanied by marked shifts in Fe-related bacterial communities (Xiao et al., 2021 ), promoting Fe reduction alongside Fe p depletion and Fe o crystallization (with Fe crystalline ratio increase magnitudes in both ​upper soil layer​ and ​lower soil layer​ exceeding 100%) (Khandakar et al., 2021 ; Lin et al., 2024 ; Liu et al., 2021 ). OC:Fe decreases due to SOC loss and reduced Fe oxides, ultimately leading to Fe-OC depletion. Thus, post-conversion strategies such as revegetation (prioritizing plants with high root ROL), could enhance soil SOC, improve soil aeration and oxidizing conditions, regulate Fe-related bacterial communities, and promote Fe oxidation. This would increase the availability of Fe o and Fe p for binding with organic carbon, restore Fe-OC pool, and achieve long-term stabilization and enhancement of soil carbon sinks. 5. Conclusion This study revealed that the conversion of estuarine natural wetlands into aquaculture ponds induced significant changes in the soil Fe-related bacterial community, and the interaction between Fe and carbon undergo significant changes. After the soil use change, soil Fe-OC content and OC:Fe ratio significantly decreased, accompanied by reduction in Fe activation index and Fe complexing index, and a marked increase in the Fe crystalline ratio significantly. However, these changes vary depending on wetland characteristics, such as ROL from roots and physicochemical properties, resulting in site-specific differences in the extent of of Fe-OC and OC:Fe depletion. Notably, the conversion of Kandelia candel wetlands led to the greatest losses, with Fe-OC in the lower soil layer declining by 187.95% and OC:Fe in the upper layer decreasing by 80.90%. Soil Fe o , Fe p , and Fe-OC are driving factors regulating Fe-reducing bacterial communities, while Fe-related bacteria, in turn, mediate the transformation of various Fe oxides by influencing the Fe cycling process. Fe oxides (mainly Fe o and Fe p ) influenced Fe-OC formation directly or indirectly by modulating OC:Fe ratios. In natural wetlands, Fe-OC is strongly correlated with Fe o ( p < 0.001), whereas in aquaculture ponds, Fe-OC also shows a significant correlation with Fe p ( p < 0.01), suggesting a shift in Fe-OC formation pathways under reducing conditions. Overall, the conversion of estuarine natural wetlands to aquaculture ponds alters Fe-related bacterial communities, enhances Fe reduction, Fe p depletion, and Fe o crystallization, ultimately driving Fe-OC loss. Restoration strategies, such as reintroducing vegetation with high root ROL, are critical for mitigating Fe oxide depletion, reversing crystallization, and stabilizing soil carbon pools in estuarine wetlands. Declarations Acknowledgment This work was financially supported by the National Key R&D Program of China (2023YFE0113100) and the National Natural Science Foundation of China (42141014). CRediT authorship contribution statement Junpeng Li: Writing-original draft, Visualization, Conceptualization, Software, Data curation. Qingsong Zeng: Visualization, Formal analysis, Conceptualization. Shuling Tang: Writing-review and editing. Yingzi Wu: Writing-review and editing. Yi Zheng: Writing-review and editing, Methodology. Weiqi Wang: Writing-review and editing, Methodology, Resources, Project administration, Validation, Funding acquisition. Peipei Xue: Writing-review and editing, Methodology. Jordi Sardans: Writing-review and editing, Investigation, Supervision. Josep Peñuelas: Writing-review and editing, Investigation, Supervision. Declaration of competing interest The authors declared that there is no conflict of interest. Data availability Data will be made available on request. 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CATENA 223, 106937. https://doi.org/10.1016/j.catena.2023.106937 Zecchin, S., Corsini, A., Martin, M., Romani, M., Beone, G.M., Zanchi, R., Zanzo, E., Tenni, D., Fontanella, M.C., Cavalca, L., 2017. Rhizospheric iron and arsenic bacteria affected by water regime: Implications for metalloid uptake by rice. Soil Biology and Biochemistry 106, 129–137. https://doi.org/10.1016/j.soilbio.2016.12.021 Zheng, G., Jiao, C., Zhou, S., Shang, G., 2016. Analysis of soil chronosequence studies using reflectance spectroscopy. International Journal of Remote Sensing 37, 1881–1901. https://doi.org/10.1080/01431161.2016.1163751 Supplementary Files Supplementarymaterials.docx Cite Share Download PDF Status: Published Journal Publication published 05 Dec, 2025 Read the published version in Plant and Soil → Version 1 posted Editorial decision: Major revisions 31 Aug, 2025 Reviewers agreed at journal 10 Jul, 2025 Reviewers invited by journal 10 Jul, 2025 Editor invited by journal 09 Jul, 2025 Editor assigned by journal 09 Jul, 2025 First submitted to journal 07 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7067479","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":483500595,"identity":"b32fe111-bd71-46d4-be3a-72d7b6b4f47b","order_by":0,"name":"Junpeng Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvklEQVRIiWNgGAWjYBACPgYG9h8fKv7JsbG3HyBOCxsQS844c8CYj+dMAvFapHnbDiTOk3AwIFKLRI6BAc+ZO+ltEgwJDD8qthGjJS0hQaLiWW6bdOMBxp4zt4nRknzggMEZ5tw2mQMJzIxtRGlJbGxIbGNOZ5NIMCBWS/JhhoNthxNI0MLzLI2x4UyaYRswkA8S5Rd+9hwz5j8VNvLy7e0HH/yoIEILg0ACgn2ACPUga4hUNwpGwSgYBSMYAAAyVzvSYkceOgAAAABJRU5ErkJggg==","orcid":"","institution":"Fujian Normal University","correspondingAuthor":true,"prefix":"","firstName":"Junpeng","middleName":"","lastName":"Li","suffix":""},{"id":483500596,"identity":"c48db4e6-f799-41e4-9e53-5842d09cb048","order_by":1,"name":"Qingsong Zeng","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Qingsong","middleName":"","lastName":"Zeng","suffix":""},{"id":483500597,"identity":"05bfc5dc-6b88-4db4-a7af-404024f81bc6","order_by":2,"name":"Shuling Tang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Shuling","middleName":"","lastName":"Tang","suffix":""},{"id":483500598,"identity":"5d5c00f0-485e-4ebf-9458-7397f585b7d4","order_by":3,"name":"Yingzi Wu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Yingzi","middleName":"","lastName":"Wu","suffix":""},{"id":483500599,"identity":"c1917d84-c22b-4362-bf30-cd5a94fb0558","order_by":4,"name":"Yi Zheng","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Zheng","suffix":""},{"id":483500600,"identity":"db01a24d-8dcb-45ac-a099-8600e095ffaf","order_by":5,"name":"Weiqi Wang","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Weiqi","middleName":"","lastName":"Wang","suffix":""},{"id":483500601,"identity":"8cdf4e36-1d6e-445d-94a5-e62541fc91de","order_by":6,"name":"Peipei Xue","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Peipei","middleName":"","lastName":"Xue","suffix":""},{"id":483500602,"identity":"ae073d91-fa4a-45e1-a3ed-bae485f6bcf8","order_by":7,"name":"Jordi Sardans","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Jordi","middleName":"","lastName":"Sardans","suffix":""},{"id":483500603,"identity":"68702c28-cfaa-4821-a56b-8e5ab21b2283","order_by":8,"name":"Josep Peñuelas","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Josep","middleName":"","lastName":"Peñuelas","suffix":""}],"badges":[],"createdAt":"2025-07-07 16:29:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7067479/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7067479/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11104-025-08162-3","type":"published","date":"2025-12-05T15:57:59+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":86705837,"identity":"42555886-710f-40f3-adf4-0ff007bb1e79","added_by":"auto","created_at":"2025-07-14 17:13:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":350790,"visible":true,"origin":"","legend":"\u003cp\u003eMap of the study area and location of sampling sites\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/2018b6402547f3e4551c6f5d.png"},{"id":86705847,"identity":"ec4b4cae-59bd-4c7b-bc8f-4f0dd3bc7a5b","added_by":"auto","created_at":"2025-07-14 17:13:14","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":179062,"visible":true,"origin":"","legend":"\u003cp\u003eSoil Fe characteristic parameters before and after estuarine wetlands are converted into aquaculture ponds. Lowercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) between natural wetlands and aquaculture ponds for the same soil layer and site.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/a4b59a166126c2fe1d69bfe5.png"},{"id":86706175,"identity":"6f11bea3-de20-455e-befd-0f86d5553bdb","added_by":"auto","created_at":"2025-07-14 17:21:14","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":182427,"visible":true,"origin":"","legend":"\u003cp\u003eContent of soil Fe-bound organic carbon (Fe-OC) before and after estuarine wetlands are converted into aquaculture ponds. Uppercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) for the same soil layer across different sites within natural wetlands or aquaculture ponds, lowercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) between natural wetlands and aquaculture ponds for the same soil layer and site.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/99b1dbf9811301ead7d2f704.png"},{"id":86705840,"identity":"a8cec161-ba60-4d92-b77d-aeb94221440f","added_by":"auto","created_at":"2025-07-14 17:13:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":245880,"visible":true,"origin":"","legend":"\u003cp\u003eProportion of soil Fe-OC (\u003cem\u003ef\u003c/em\u003e\u003csub\u003eFe-OC\u003c/sub\u003e) before and after estuarine wetlands are converted into aquaculture ponds. Uppercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) for the same soil layer across different sites within natural wetlands or aquaculture ponds, lowercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) between natural wetlands and aquaculture ponds for the same soil layer and site.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/6a95a3d5335cf4a4c520f382.png"},{"id":86706174,"identity":"8a929605-ed12-4812-aad8-ccbd49039cec","added_by":"auto","created_at":"2025-07-14 17:21:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":223583,"visible":true,"origin":"","legend":"\u003cp\u003eSoil Molar OC:Fe rations before and after the transformation of estuarine wetland to aquaculture pond. Uppercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) for the same soil layer across different sites within natural wetlands or aquaculture ponds, lowercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05) between natural wetlands and aquaculture ponds for the same soil layer and site.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/62a31c446b300b1376228974.png"},{"id":86706180,"identity":"f0d66f19-b1c9-468d-bafd-7da1c0c06e13","added_by":"auto","created_at":"2025-07-14 17:21:14","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":837868,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation analysis of various environmental factors before and after the estuarine wetland was converted into aquaculture ponds. * indicates significance at the 0.05 level, ** indicates significance at the 0.01 level, *** indicates significance at the 0.001 level. Fe(Ⅱ), divalent Fe; Fe(Ⅲ), trivalent Fe; HCl-Fe\u003csub\u003et\u003c/sub\u003e, total Fe extracted by hydrochloric acid; Fe(Ⅲ)/Fe(Ⅱ), ratio of trivalent Fe to divalent Fe content; Fe\u003csub\u003ed\u003c/sub\u003e, free Fe oxides; Fe\u003csub\u003eo\u003c/sub\u003e, amorphous Fe oxides; Fe\u003csub\u003ep\u003c/sub\u003e, complexed Fe oxides; Fe-OC, Fe-bound organic carbon; \u003cem\u003ef\u003c/em\u003eFe-OC, proportion of Fe-bound organic carbon to total organic carbon; OC:Fe, molar OC:Fe rations; Fe-AI, Fe activation index; Fe-CI, Fe complexing index; Fe-CR, Fe crystalline ratio.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/5de013053f7817f9db7d72d1.png"},{"id":86705844,"identity":"a7ddaa04-c4bb-4796-852e-1c67414af116","added_by":"auto","created_at":"2025-07-14 17:13:14","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":184819,"visible":true,"origin":"","legend":"\u003cp\u003ePCoA analysis of soil FeRB(a) and FeOB(b). MJ, Minjiang Estuary; JL, Jiulong Estuary; Zhangjiang Estuary; PAW, \u003cem\u003ePhragmites australis \u003c/em\u003eWetland; ACW, \u003cem\u003eAegiceras corniculatum\u003c/em\u003e Wetland; KCW,\u003cem\u003eKandelia candel\u003c/em\u003e Wetland; AP, aquaculture pond.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/06b5166f7ea5b6f559f127bd.png"},{"id":86705854,"identity":"d026cb39-0ab1-4fa6-81a7-994e43cd898f","added_by":"auto","created_at":"2025-07-14 17:13:14","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":70729,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Family-level community structure of soil FeRB;\u003cstrong\u003e \u003c/strong\u003e(b) Family-level community structure of soil FeOB. MJ, Minjiang Estuary; JL, Jiulong Estuary; Zhangjiang Estuary; PAW, \u003cem\u003ePhragmites australis \u003c/em\u003eWetland; ACW, \u003cem\u003eAegiceras corniculatum\u003c/em\u003e Wetland; KCW,\u003cem\u003e Kandelia candel\u003c/em\u003eWetland; AP, aquaculture pond.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/3b37d3d2c262b4c1246a0f27.png"},{"id":86705848,"identity":"788eebdd-5496-43f7-9ed0-f85da92a704a","added_by":"auto","created_at":"2025-07-14 17:13:14","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":252900,"visible":true,"origin":"","legend":"\u003cp\u003e(a)Redundancy analysis of FeRB; (b)Redundancy analysis of FeOB; (c)PLS-SEM analysis of Fe-related bacteria and Fe and Fe-OC. Fe(Ⅱ), divalent Fe; Fe(Ⅲ), trivalent Fe; HCl-Fe\u003csub\u003et\u003c/sub\u003e, total Fe extracted by hydrochloric acid; Fe(Ⅲ)/Fe(Ⅱ), ratio of trivalent Fe to divalent Fe content; Fe\u003csub\u003ed\u003c/sub\u003e, free Fe oxides; Fe\u003csub\u003eo\u003c/sub\u003e, amorphous Fe oxides; Fe\u003csub\u003ep\u003c/sub\u003e, complexed Fe oxides; Fe-OC, Fe-bound organic carbon; OC:Fe, molar OC:Fe rations. *, **, and *** indicate statistical significance at \u003cem\u003ep\u003c/em\u003e\u0026lt;0.05, \u003cem\u003ep\u003c/em\u003e\u0026lt;0.01, and \u003cem\u003ep\u003c/em\u003e\u0026lt;0.001, respectively.\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/1c153fe4268fae828914d077.png"},{"id":86705850,"identity":"e1e59dd3-870d-4a06-84d1-b5c36cc6a865","added_by":"auto","created_at":"2025-07-14 17:13:14","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":190632,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of the impact of soil Fe-related bacteria, Fe and Fe-OC during the transformation of estuarine natural wetland into aquaculture pond.\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/02d612e184f64e0be13e129d.png"},{"id":97723907,"identity":"7e32fe53-5da8-49ee-8136-950ba65102de","added_by":"auto","created_at":"2025-12-08 16:09:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4226439,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/b6af7e40-b46d-45af-8d4f-14cbc30768cd.pdf"},{"id":86705841,"identity":"6286e383-bd69-4805-bdac-4817bfa26815","added_by":"auto","created_at":"2025-07-14 17:13:13","extension":"docx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":21155,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-7067479/v1/c1943dd25315cc6f360d6d46.docx"}],"financialInterests":"","formattedTitle":"Coupled shifts in microbial and mineralogical Fe cycling destabilize organic carbon in converted estuarine wetlands","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eEstuarine wetlands, located at the interface of land, rivers, and oceans, are unique transitional ecosystems with diverse ecological functions. Their high productivity and the low sediment decomposition rates make them important and stable organic carbon sinks (Mei et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Yan et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, rapid population growth in recent times has driven increased demand for seafood, prompting a significant expansion of coastal aquaculture. Studies have shown that from 1985 to 2015, the area of coastal wetlands in China decreased from 10,262 km\u0026sup2; to 7,296 km\u0026sup2;, while the area of aquaculture ponds more than doubled\u0026mdash;from 2,305 km\u0026sup2; to 4,431 km\u0026sup2; (Hu et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003ea; Wang et al., \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe conversion of estuarine wetlands into aquaculture ponds involves the removal of native vegetation and a marked increase in human disturbance. This transition alters key soil physicochemical properties\u0026mdash;such as redox potential, pH, moisture content, and bulk density\u0026mdash;and can significantly impact carbon pool stability (Hou et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). For example, studies have shown that soil bulk density increases while porosity declines following such land-use change, reducing soil aeration and water-holding capacity. These changes lead to a significant loss of soil organic carbon content (Lin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In addition, the diversity and stability of soil microbial communities tend to decrease after this land use conversion, which may further exacerbate changes in soil properties and carbon loss (Hou et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn wetland soils, organic carbon can form stable complexes with Fe oxides (Fe-OC) through adsorption or co-precipitation, making the organic carbon difficult for microbial decomposition. This binding mechanism significantly enhances the long-term storage of organic carbon (Han et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2022a\u003c/span\u003e). The redox cycling of Fe is a key process regulating Fe-bound organic carbon, with Fe-related bacteria (including Fe-oxidizing and Fe-reducing bacteria) playing critical roles. Under anaerobic conditions, Fe-reducing bacteria (FeRB) reduce Fe(Ⅲ) to Fe(Ⅱ), releasing organic carbon bound to Fe oxides and promoting organic carbon degradation (K\u0026uuml;gler et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Conversely, in oxidative environments, Fe-oxidizing bacteria (FeOB) oxidize Fe(Ⅱ), facilitating the reformation of Fe-OC complexes (Emerson et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The oxidation states of Fe in soil mainly include free Fe oxides (Fe\u003csub\u003ed\u003c/sub\u003e), amorphous Fe oxides (Fe\u003csub\u003eo\u003c/sub\u003e), and complexed Fe oxides (Fe\u003csub\u003ep\u003c/sub\u003e). Among these, Fe\u003csub\u003ed\u003c/sub\u003e is highly stable and functions as a key mineral cementing agent, but its low specific surface area limits its ability to adsorb organic carbon. In contrast, Fe\u003csub\u003eo\u003c/sub\u003e has a much larger surface area and higher reactivity, providing strong adsorption capacity and making it more effective at stabilizing organic carbon. Fe\u003csub\u003ep\u003c/sub\u003e refers to iron bound to organic matter (e.g., humus) or inorganic soil components, where organic ligands mediate Fe\u0026ndash;organic carbon bridging through coordination bonds, thereby enhancing the stability of organic carbon (Azadi et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Rezapour et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Xue et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). However, the mechanisms by which Fe-related bacteria regulate different Fe oxide forms and influence Fe-organic carbon binding remains poorly understood. Due to the unique tidal effects, estuarine wetlands experience frequent changes in soil redox conditions, which promote the Fe redox cycling process and enable the stable existence of Fe-bound organic carbon (Hu et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). However, converting such natural wetlands into aquaculture ponds disrupts the original redox conditions and Fe cycling processes of estuarine wetlands, thereby affecting the interaction between Fe and organic carbon.\u003c/p\u003e\u003cp\u003eThe study of Fe-OC has recently gained attention as a key indicator of carbon pool stability in natural wetlands (Bi et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Lin et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; X. Liu et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). For example, research on \u003cem\u003ePhragmites australis\u003c/em\u003e wetlands in the Yangtze River estuary revealed that the Fe-OC accumulation increased significantly under the flooding and high salinity stress (Bi et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Microbial activity has also been identified as a major contributor to Fe-OC formation (Liu et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In freshwater wetlands, vegetation type has been shown to influence the accumulation of Fe-bound organic carbon (Chen et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, limited studies have explored the transformation of Fe-OC and its driving factors during the transformation of natural wetlands to aquaculture ponds.\u003c/p\u003e\u003cp\u003eIn this study, we investigated typical estuarine wetlands in China to examine the changes in Fe content, Fe-OC and Fe-related bacterial communities across three different vegetation types, namely, \u003cem\u003ePhragmites australis\u003c/em\u003e, \u003cem\u003eAegiceras corniculatum\u003c/em\u003e, \u003cem\u003eKandelia candel\u003c/em\u003e. These changes were assessed during the transition from oxidized, looser soils to reduced, compacted soils following the conversion of natural wetlands into aquaculture ponds. The aim was to clarify the interactions among Fe-related bacteria, various types of Fe, and Fe-OC throughout this transformation process. By identifying how land use change influences Fe-OC dynamics and the key driving factors, this study provides insights into strategies for enhancing the stability of carbon pools in estuarine wetlands.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Study Area and Soil Sampling\u003c/h2\u003e\u003cp\u003eThis study was conducted in three estuarine natural wetlands (NW) and their reclaimed aquaculture ponds (AP) located in the Min River Estuary (MJ), Zhang River Estuary (ZJ), and Jiu Long River Estuary (JL) in Fujian, China (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Detailed information on each sampling site is shown in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. All sampling sites are located within subtropical monsoon climate zone. The Min River Estuary area has an average annual temperature of 19.6 ℃ and average annual precipitation of 1346 mm; the Zhang River Estuary area has an average annual temperature of 21.0 ℃ and average annual precipitation of 1371 mm; the Jiu Long River Estuary area has an average annual temperature of 21.2 ℃ and average annual precipitation of 1714.5 mm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFrom October to December 2021, five plots (10 m \u0026times; 10 m square) were randomly selected at each site and for each environmental type. Within each plot, one sub-plot (1 m \u0026times; 0.6 m) was chosen, and soil samples were collected from the upper layer (0\u0026ndash;15 cm) and lower layer (15\u0026ndash;30 cm) using a soil sampler with a diameter of 9 cm. A total of 60 samples were collected (3 sampling sites \u0026times; 2 environment types \u0026times; 2 soil layers \u0026times; 5 replicates). Samples were immediately stored in sterile bags under refrigerated conditions and transported back to the laboratory. In the laboratory, soil samples were homogenized, and stones and plant roots were removed using a 2 mm sieve. Each soil sample was divided into two parts: one part was air-dried and ground through a 0.15 mm sieve for determination of soil Fe fractions and Fe-OC content; the other part was stored as moist soil at -20℃ for analysis of soil Fe-oxidizing bacteria (FeOB) and Fe-reducing bacteria (FeRB) communities.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Determination of Fe in the soil by valence and by form\u003c/h2\u003e\u003cp\u003eThe valence state Fe in soil samples was extracted using 0.5 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e HCl. The samples were divided into two parts: one part was used to determine Fe(Ⅱ), and the other part was used to determine the total Fe extracted by hydrochloric acid (HCl-Fe\u003csub\u003et\u003c/sub\u003e). The Fe(Ⅲ) content was calculated as the difference between Fe(Ⅱ) and HCl-Fe\u003csub\u003et\u003c/sub\u003e (Liu et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Free Fe oxides in the soil (Fe\u003csub\u003ed\u003c/sub\u003e) were obtained by the DCB (Dithionite-Citrate-Bicarbonate) reduction dissolution method. Amorphous Fe oxides (Fe\u003csub\u003eo\u003c/sub\u003e) were extracted using 0.2 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ammonium oxalate buffer solution (pH\u0026thinsp;\u0026asymp;\u0026thinsp;3.2). Complexed Fe oxides in the soil (Fe\u003csub\u003ep\u003c/sub\u003e) were extracted using 0.1 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e sodium pyrophosphate solution (pH\u0026thinsp;=\u0026thinsp;8.5) (Yao et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The Fe content in all extracted forms was determined as follows: an appropriate amount of extract was taken, and except for the extract used to determine Fe(Ⅱ), a certain amount of hydroxylamine hydrochloride was added to the other extracts to reduce Fe to divalent Fe. After sufficient reaction, a certain amount of sodium acetate and o-phenanthroline solution was added for color development. The optical density (OD) value was measured at 510 nm wavelength using a UV spectrophotometer. The content of each valence state and form of Fe was then calculated based on the sample OD value and standard sample OD value curve (Lin et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The formulas for calculating the Fe activation index (Fe-AI), Fe complexing index (Fe-CI), and Fe crystalline ratio (Fe-CR) are as follows (Jia et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Zheng et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2016\u003c/span\u003e):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:Fe\\:activation\\:index\\:\\left(\\%\\right)\\:=\\:({Fe}_{o}\\:/\\:{Fe}_{d})\\:\\times\\:\\:100\\%\\:$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:Fe\\:complexing\\:index\\:\\left(\\%\\right)\\:=\\:({Fe}_{p}\\:/\\:{Fe}_{d})\\:\\times\\:\\:100\\%$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:Fe\\:crystalline\\:ratio\\:=\\:({Fe}_{d}\\:-\\:{Fe}_{o})\\:/\\:{Fe}_{o}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFe-bound organic carbon in soil (Fe-OC) was determined by the organic carbon-bound precipitate generated during the DCB method extraction of free Fe oxides. However, as some water-soluble organic carbon may be produced during extraction, a control experiment is required for adjusting. In this experiment, a 1.6 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e NaCl solution was used to replace sodium citrate in the DCB method to treat soil samples. The total organic carbon content in the precipitates obtained from both treatments was then measured using a Vario EL III carbon-nitrogen element analyzer (Lin et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The calculation formulas for Fe-bound organic carbon (Fe-OC), the proportion of Fe-bound organic carbon in organic carbon (\u003cem\u003ef\u003c/em\u003e\u003csub\u003eFe\u0026minus;OC\u003c/sub\u003e), and the molar OC:Fe rations (OC:Fe) are as follows (Tian and Lu, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e):\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$\\:Fe-OC\\:(g/kg)\\:={\\:OC}_{NaCl}\\:-\\:{OC}_{DCB}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$$\\:{f}_{Fe-OC\\:}\\left(\\%\\right)\\:=\\:Fe-OC\\:/\\:SOC\\:\\times\\:\\:100\\%$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equf\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equf\" name=\"EquationSource\"\u003e\n$$\\:OC/Fe\\:=\\:(Fe-OC\\:\\times\\:\\:{M}_{Fe})\\:/\\:({M}_{C}\\:\\times\\:\\:{m}_{{Fe}_{d}})$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eOC\u003csub\u003eNaCl\u003c/sub\u003e: Organic carbon content in the precipitate after NaCl solution treatment; OC\u003csub\u003eDCB\u003c/sub\u003e: Organic carbon content in the precipitate after DCB method treatment; M\u003csub\u003eC\u003c/sub\u003e: Molar mass of carbon atoms; M\u003csub\u003eFe\u003c/sub\u003e: Molar mass of Fe atoms; m\u003csub\u003eFed\u003c/sub\u003e: Content of free Fe oxides.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Determination of soil microorganisms\u003c/h2\u003e\u003cp\u003eSoil DNA was extracted from wetland soil samples using the CTAB(Cetyltrimethylammonium Bromide) method. The purity and concentration of extracted DNA were assessed via agarose gel electrophoresis. Subsequently, an appropriate volume of genomic DNA was diluted to 1 ng\u0026middot;\u0026micro;L⁻\u0026sup1; using sterile ultrapure water. The diluted DNA served as template for PCR amplification, targeted at the V3-V4 region of 16S rRNA using 341F (CCTAYGGGRBGCASCAG) and 806R (GGACTACNNGGGGTATCTAAT) as primers (Hossen et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Maretto et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe PCR products were analyzed by agarose gel electrophoresis at 2% for 40 min. Aliquots were mixed according to the concentration of the PCR products, and the products were purified by agarose gel electrophoresis using 1\u0026times;TAE at 2% concentration to cut and recover the target bands. The PCR product purification kit used in this process was Thermo Scientific GeneJET gel recovery kit. The library was constructed using the Ion Plus Fragment Library Kit 48rxns from Thermofisher, the constructed library was quantified by Qubit, and after the library was tested and qualified, it was sequenced using the Life Ion S5TM from Thermofisher platform(Inc., USA).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Data Analysis\u003c/h2\u003e\u003cp\u003eThe data on Fe-related bacteria were based on the classification results of soil bacterial communities and the taxonomic names of Fe-related bacteria from known literature databases (Peng et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Standard errors of Fe contents, Fe-OC related indicators, and alpha diversity indices of Fe-related bacteria were calculated using Excel2019. Origin2024 was used for one-way ANOVA on various Fe contents, Fe oxides characteristic parameters, Fe-OC related indicators, and alpha diversity indices of Fe-related bacteria to compare content changes among different environmental types within the same site and soil layer, and to create charts. Two-way ANOVA in the same software was used to compare differences in soil layer data influenced by site, environmental type, and their interaction (site \u0026times; environmental type). The \u0026lsquo;GGally\u0026rsquo; package was used to analyze correlations among various Fe contents, Fe oxides characteristic parameters, and Fe-OC related indicators in R4.3.2. The \u0026lsquo;vegan\u0026rsquo; package was used for PCoA analysis of Fe-related bacterial communities, and Adonis was used to compare differences in Fe-related bacterial communities in soils of different environmental types at the same site. The package was also used for redundancy analysis of Fe-related bacteria and environmental factors to determine the influencing factors of Fe-related bacteria. The \u0026lsquo;plspm\u0026rsquo; package was used for PLS-SEM analysis of Fe-related bacterial communities, various Fe contents, OC:Fe, and Fe-OC, with Fe-related bacterial communities characterized by Shannon and Chao1 indices. The model was initially established based on previous studies and further optimized according to calculation results.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003e\u003cb\u003e3.1. Fe content and characteristic parameters of soil types before and after conversion of estuarine wetlands to aquaculture ponds\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAmong the three types of estuarine natural wetland soils, the contents of Fe(Ⅱ) and Fe\u003csub\u003ep\u003c/sub\u003e in \u003cem\u003eKandelia candel\u003c/em\u003e wetlands were significantly higher than those in \u003cem\u003ePhragmites australis\u003c/em\u003e and \u003cem\u003eAegiceras corniculatum\u003c/em\u003e wetlands (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). After conversion to aquaculture ponds, Fe(Ⅱ) content increased by more than 65% relative to natural wetlands in all soil layers, while Fe(Ⅲ) content decreased by more than 18% (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). A pronounced decline was observed in Fe oxides (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In the upper soil layer, Fe\u003csub\u003ed\u003c/sub\u003e content decreased from 19.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36 to 17.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53 g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Meanwhile, Fe\u003csub\u003ed\u003c/sub\u003e in the lower soil layer declined from 19.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48 to 17.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.44 g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Fe\u003csub\u003eo\u003c/sub\u003e and Fe\u003csub\u003ep\u003c/sub\u003e showed more significant decreases compared to natural wetlands (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In the upper soil layer, Fe\u003csub\u003eo\u003c/sub\u003e content declined by 32.15%, and Fe\u003csub\u003ep\u003c/sub\u003e by 51.96%. In the lower layer, Fe\u003csub\u003eo\u003c/sub\u003e decreased by 29.98%, with Fe\u003csub\u003ep\u003c/sub\u003e reduction reaching 27.73%. Two-way ANOVA results (Table S2) indicated that in the upper soil layer, site​ significantly affected Fe(Ⅱ)、Fe(Ⅲ)、Fe(Ⅲ)/ Fe(Ⅱ)、Fe\u003csub\u003eo\u003c/sub\u003e、Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), while environment type significantly affected Fe(Ⅱ), Fe(Ⅲ), Fe\u003csub\u003ed\u003c/sub\u003e, Fe\u003csub\u003eo\u003c/sub\u003e, and Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). The interaction between environment type and site significantly influenced Fe(Ⅱ), Fe(Ⅲ)/Fe(Ⅱ), Fe\u003csub\u003ed\u003c/sub\u003e, Fe\u003csub\u003eo\u003c/sub\u003e, and Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In the lower soil layer, site​ significantly affected Fe(Ⅱ)、Fe(Ⅲ)、Fe(Ⅲ)/ Fe(Ⅱ)、Fe\u003csub\u003eo\u003c/sub\u003e、Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), while environment type significantly affected Fe(Ⅱ), Fe(Ⅲ), HCl-Fet, Fe(Ⅲ)/Fe(Ⅱ), Fe\u003csub\u003ed\u003c/sub\u003e, Fe\u003csub\u003eo,\u003c/sub\u003e and Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The interaction between environment type and site significantly impacted Fe(Ⅱ), Fe(Ⅲ)/Fe(Ⅱ), Fe\u003csub\u003eo\u003c/sub\u003e, and Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).Fe(Ⅱ), Fe(Ⅲ)/Fe(II), Fe\u003csub\u003eo\u003c/sub\u003e, and Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFe content of various types before and after the transformation of estuarine wetlands into aquaculture ponds in different regions. MJ, Minjiang Estuary; JL, Jiulong Estuary; Zhangjiang Estuary; Total, overall of each sampling point; PAW, \u003cem\u003ePhragmites australis\u003c/em\u003e Wetland; ACW, \u003cem\u003eAegiceras corniculatum\u003c/em\u003e Wetland; KCW, \u003cem\u003eKandelia candel\u003c/em\u003e Wetland; NW, natural wetland; AP, aquaculture pond; Fe(Ⅱ), divalent Fe, g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Fe(Ⅲ), trivalent Fe, g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; HCl-Fe\u003csub\u003et\u003c/sub\u003e, total Fe extracted by hydrochloric acid, g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Fe(Ⅲ)/Fe(Ⅱ), ratio of trivalent Fe to divalent Fe content; Fe\u003csub\u003ed\u003c/sub\u003e, free Fe oxides, g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Fe\u003csub\u003eo\u003c/sub\u003e, amorphous Fe oxides, g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; Fe\u003csub\u003ep\u003c/sub\u003e, complexed Fe oxides, g\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SE, uppercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) for the same soil layer across different sites within natural wetlands or aquaculture ponds, lowercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) between natural wetlands and aquaculture ponds for the same soil layer and site.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"10\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSite\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSoil layer\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEnvironmental type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eFe(Ⅱ)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eFe(Ⅲ)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eHCl- Fe\u003csub\u003et\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eFe(Ⅲ)/ Fe(Ⅱ)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eFe\u003csub\u003ed\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eFe\u003csub\u003eo\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eFe\u003csub\u003ep\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eMJ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e0\u0026ndash;15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePAW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.83\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e14.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.95\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e10.66\u0026thinsp;\u0026plusmn;\u0026thinsp;1.98\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e18.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e9.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.269\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.99\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e13.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.80\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e21.19\u0026thinsp;\u0026plusmn;\u0026thinsp;6.70\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e18.37\u0026thinsp;\u0026plusmn;\u0026thinsp;1.23\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e10.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.39\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.256\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e15\u0026ndash;30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePAW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.22\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e13.83\u0026thinsp;\u0026plusmn;\u0026thinsp;1.10\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e10.89\u0026thinsp;\u0026plusmn;\u0026thinsp;0.89\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19.68\u0026thinsp;\u0026plusmn;\u0026thinsp;0.54\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e7.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.287\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10.35\u0026thinsp;\u0026plusmn;\u0026thinsp;1.08\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e7.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.85\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.87\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e9.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.293\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eJL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e0\u0026ndash;15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eACW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.55\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.59\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e18.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e20.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e9.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.432\u0026thinsp;\u0026plusmn;\u0026thinsp;0.013\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.10\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11.32\u0026thinsp;\u0026plusmn;\u0026thinsp;1.07\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e12.93\u0026thinsp;\u0026plusmn;\u0026thinsp;1.69\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e9.43\u0026thinsp;\u0026plusmn;\u0026thinsp;0.52\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.448\u0026thinsp;\u0026plusmn;\u0026thinsp;0.024\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e15\u0026ndash;30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eACW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.83\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e32.43\u0026thinsp;\u0026plusmn;\u0026thinsp;8.00\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e15.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e3.39\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.241\u0026thinsp;\u0026plusmn;\u0026thinsp;0.012\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.56\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e9.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15.34\u0026thinsp;\u0026plusmn;\u0026thinsp;1.08\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e16.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e3.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.244\u0026thinsp;\u0026plusmn;\u0026thinsp;0.015\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eZJ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e0\u0026ndash;15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKCW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.32\u0026thinsp;\u0026plusmn;\u0026thinsp;1.01\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e13.75\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e8.72\u0026thinsp;\u0026plusmn;\u0026thinsp;0.86\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e20.37\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e10.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e1.447\u0026thinsp;\u0026plusmn;\u0026thinsp;0.127\u003csup\u003eCa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.39\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003csup\u003eABa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e5.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.86\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e10.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.81\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.725\u0026thinsp;\u0026plusmn;\u0026thinsp;0.019\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e15\u0026ndash;30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eKCW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.00\u0026thinsp;\u0026plusmn;\u0026thinsp;1.34\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e12.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.39\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.41\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e8.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.503\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021\u003csup\u003eCa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.43\u003csup\u003eCb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.47\u0026thinsp;\u0026plusmn;\u0026thinsp;1.09\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.43\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e2.07\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003csup\u003eBa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.81\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00\u003csup\u003eAa\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e8.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003csup\u003eAb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.494\u0026thinsp;\u0026plusmn;\u0026thinsp;0.007\u003csup\u003eBb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eTotal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e0\u0026ndash;15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e13.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e12.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.30\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e9.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.716\u0026thinsp;\u0026plusmn;\u0026thinsp;0.145\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.87\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.76\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.70\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15.12\u0026thinsp;\u0026plusmn;\u0026thinsp;4.22\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e6.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.344\u0026thinsp;\u0026plusmn;\u0026thinsp;0.031\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e15\u0026ndash;30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10.78\u0026thinsp;\u0026plusmn;\u0026thinsp;0.65\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e11.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.57\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e13.34\u0026thinsp;\u0026plusmn;\u0026thinsp;2.72\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e19.35\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e10.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.36\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.476\u0026thinsp;\u0026plusmn;\u0026thinsp;0.052\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.83\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e8.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e10.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.61\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e8.27\u0026thinsp;\u0026plusmn;\u0026thinsp;1.52\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e17.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.44\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e7.21\u0026thinsp;\u0026plusmn;\u0026thinsp;0.78\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e0.344\u0026thinsp;\u0026plusmn;\u0026thinsp;0.029\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAfter the estuarine natural wetlands were converted into aquaculture ponds, in the upper soil layer, Fe activation index showed a ​25.60% reduction relative to the baseline of natural wetlands​ (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). Fe complexing index showed a ​45.40% reduction relative to the baseline of natural wetlands (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Fe crystalline ratio showed a ​103.96% increase relative to the baseline of natural wetlands (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). In the lower soil layer, Fe activation index showed a ​21.59% reduction relative to the baseline of natural wetlands (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). Fe complexing index showed a ​28.44% reduction relative to the baseline of natural wetlands (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee). Fe crystalline ratio showed a ​117.02% increase relative to the baseline of natural wetlands (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Characteristics of soil Fe-OC before and after estuarine wetlands are converted into aquaculture ponds\u003c/h2\u003e\u003cp\u003eIn various estuarine natural wetlands, the Fe-OC content and OC:Fe in \u003cem\u003eKandelia candel\u003c/em\u003e wetland soils were significantly higher than those in \u003cem\u003ePhragmites australis\u003c/em\u003e wetlands and \u003cem\u003eAegiceras corniculatum\u003c/em\u003e Wetlands (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). After conversion to aquaculture ponds, the ​upper soil layer​ Fe-OC content relatively decreased by 54.30% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea), with OC:Fe declining from 0.61 to 0.31 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). These changes were significantly influenced by site, environmental type, and their interaction (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In the ​lower soil layer​ Fe-OC content relatively decreased by 64.62% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb), with OC:Fe dropping from 0.65 to 0.26 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), significantly affected by site and environmental type (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Additionally, the \u003cem\u003ef\u003c/em\u003e\u003csub\u003eFe\u0026minus;OC\u003c/sub\u003e proportion increased after wetland conversion, with site showing a significant effect in the lower layer (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cb\u003e3.3. Correlation characteristics of soil Fe-OC and Fe before and after estuarine wetlands are converted into aquaculture ponds\u003c/b\u003e\u003c/p\u003e\u003cp\u003eIn the overall process of estuarine wetland transformation into aquaculture ponds (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), Fe-OC is significantly positively correlated with OC:Fe, Fe\u003csub\u003ed\u003c/sub\u003e, Fe\u003csub\u003eo\u003c/sub\u003e, Fe\u003csub\u003ep\u003c/sub\u003e, Fe-AI, and Fe-CI (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and significantly negatively correlated with Fe-CR (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). OC:Fe is significantly positively correlated with Fe\u003csub\u003ed\u003c/sub\u003e, Fe\u003csub\u003eo\u003c/sub\u003e, Fe\u003csub\u003ep\u003c/sub\u003e, Fe-AI, and Fe-CI (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and significantly negatively correlated with Fe-CR (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Fe(Ⅱ) is significantly positively correlated with Fe-AI (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and significantly negatively correlated with Fe-CR (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Fe(Ⅲ) is significantly positively correlated with Fe\u003csub\u003ed\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Meanwhile, before land use change (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), Fe-OC is only significantly positively correlated with Fe\u003csub\u003eo\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), but after transformation into aquaculture ponds (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e), Fe-OC is significantly positively correlated with Fe\u003csub\u003eo\u003c/sub\u003e, Fe\u003csub\u003ep\u003c/sub\u003e, Fe-AI, and Fe-CI (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and significantly negatively correlated with Fe-CR (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e\u003cp\u003e\u003cb\u003e3.4. Differences in the diversity of soil Fe-related bacteria communities before and after estuarine wetlands are converted into aquaculture ponds\u003c/b\u003e\u003c/p\u003e\u003cp\u003eConversion of \u003cem\u003ePhragmites australis\u003c/em\u003e wetlands to aquaculture ponds significantly reduced soil FeRB diversity indices (Sobs, Shannon, Chao1), while increasing FeOB indices (Sobs, Shannon, Chao1) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). For \u003cem\u003eAegiceras corniculatum\u003c/em\u003e wetland conversion, both FeRB and FeOB exhibited significant decreases in Sobs, Shannon, ACE, and Chao1 indices (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). For \u003cem\u003eKandelia candel\u003c/em\u003e wetlands conversion, FeRB showed reductions in Sobs and Shannon indices \u003cem\u003e(p\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAlpha diversity index of soil Fe-related bacteria. Lowercase letters indicate significant differences (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) between natural wetlands and aquaculture ponds for the same soil layer and site.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFe-related bacteria\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSampling point\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSobs\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eShannon\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eACE\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eChao1\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eCoverage(%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eFeRB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMJPAW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e125.40\u0026thinsp;\u0026plusmn;\u0026thinsp;5.12\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e185.07\u0026thinsp;\u0026plusmn;\u0026thinsp;14.12\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e179.40\u0026thinsp;\u0026plusmn;\u0026thinsp;10.31\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e94.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMJAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e107.00\u0026thinsp;\u0026plusmn;\u0026thinsp;4.64\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e181.30\u0026thinsp;\u0026plusmn;\u0026thinsp;14.31\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e151.07\u0026thinsp;\u0026plusmn;\u0026thinsp;6.16\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e95.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJLACW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e118.80\u0026thinsp;\u0026plusmn;\u0026thinsp;3.28\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e164.71\u0026thinsp;\u0026plusmn;\u0026thinsp;4.40\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e162.12\u0026thinsp;\u0026plusmn;\u0026thinsp;8.97\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e95.15\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJLAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e77.40\u0026thinsp;\u0026plusmn;\u0026thinsp;9.54\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.85\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e148.64\u0026thinsp;\u0026plusmn;\u0026thinsp;20.94\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e116.60\u0026thinsp;\u0026plusmn;\u0026thinsp;13.27\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e96.45\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eZJKCW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e112.80\u0026thinsp;\u0026plusmn;\u0026thinsp;3.08\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.55\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e182.42\u0026thinsp;\u0026plusmn;\u0026thinsp;18.38\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e174.27\u0026thinsp;\u0026plusmn;\u0026thinsp;16.16\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e94.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eZJAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e145.00\u0026thinsp;\u0026plusmn;\u0026thinsp;2.77\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e216.52\u0026thinsp;\u0026plusmn;\u0026thinsp;12.49\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e197.65\u0026thinsp;\u0026plusmn;\u0026thinsp;8.39\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e93.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eFeOB\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMJPAW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e183.20\u0026thinsp;\u0026plusmn;\u0026thinsp;5.30\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e255.14\u0026thinsp;\u0026plusmn;\u0026thinsp;12.77\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e245.47\u0026thinsp;\u0026plusmn;\u0026thinsp;5.53\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e96.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMJAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e220.00\u0026thinsp;\u0026plusmn;\u0026thinsp;4.59\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e336.71\u0026thinsp;\u0026plusmn;\u0026thinsp;25.60\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e306.70\u0026thinsp;\u0026plusmn;\u0026thinsp;16.46\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e94.88\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJLACW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e191.40\u0026thinsp;\u0026plusmn;\u0026thinsp;12.16\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e322.02\u0026thinsp;\u0026plusmn;\u0026thinsp;34.10\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e292.12\u0026thinsp;\u0026plusmn;\u0026thinsp;20.84\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e95.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJLAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e122.20\u0026thinsp;\u0026plusmn;\u0026thinsp;22.05\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e204.63\u0026thinsp;\u0026plusmn;\u0026thinsp;32.84\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e171.01\u0026thinsp;\u0026plusmn;\u0026thinsp;31.61\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e97.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eZJKCW\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e186.40\u0026thinsp;\u0026plusmn;\u0026thinsp;4.21\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e290.43\u0026thinsp;\u0026plusmn;\u0026thinsp;19.14\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e279.72\u0026thinsp;\u0026plusmn;\u0026thinsp;12.47\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e95.69\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eZJAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e193.40\u0026thinsp;\u0026plusmn;\u0026thinsp;5.84\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e286.21\u0026thinsp;\u0026plusmn;\u0026thinsp;19.57\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e262.51\u0026thinsp;\u0026plusmn;\u0026thinsp;10.34\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e\u003cp\u003e95.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThrough PCoA analysis of soil FeRB community differences in estuarine natural wetlands before and after conversion to aquaculture ponds (Fig.\u0026nbsp;7a, \u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.714, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The PCoA1 and PCoA2 axes explained 31.72% and 17.84% of the total variation, respectively. Further Adonis analysis indicated significant differences in soil FeRB among various types of estuarine natural wetlands before and after conversion to aquaculture ponds (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Table S3). Similarly, PCoA analysis of soil FeOB community differences in estuarine natural wetlands before and after conversion to aquaculture ponds (Fig.\u0026nbsp;7b, \u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.712, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The PCoA1 and PCoA2 axes explained 28.86% and 19.96% of the total variation, respectively. Further Adonis analysis demonstrated significant differences in soil FeOB among various types of estuarine natural wetlands before and after conversion to aquaculture ponds (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) (Table S3).\u003c/p\u003e\u003cp\u003e\u003cb\u003e3.5. Differences in family-level community structure of soil Fe-related bacteria before and after estuarine wetlands are converted into aquaculture ponds\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAfter various types of estuarine natural wetlands are converted into aquaculture ponds, the dominant types and relative abundances of FeRB families undergo certain changes (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea). The dominant bacterial family in \u003cem\u003ePhragmites australis\u003c/em\u003e wetlands is Desulfobacteraceae, whose relative abundance decreases from 26.7\u0026ndash;18.6% after conversion to aquaculture ponds, resulting in Thiobacillaceae becoming the dominant family in the soil of the converted aquaculture ponds, with its relative abundance increasing from 2.6\u0026ndash;23.0%. The dominant bacterial family in \u003cem\u003eAegiceras corniculatum\u003c/em\u003e wetlands is Desulfobacteraceae, whose relative abundance decreases from 48.7\u0026ndash;33.1% after conversion to aquaculture ponds. The dominant bacterial family in \u003cem\u003eKandelia candel\u003c/em\u003e Wetland is Desulfobulbaceae, whose relative abundance decreases from 37.9\u0026ndash;6.7% after conversion, leading to Anaeromyxobacteraceae becoming the dominant family in the soil of the converted aquaculture ponds, with its relative abundance increasing from less than 0.1\u0026ndash;41.5%. The relative abundance of dominant FeOB families remains relatively stable after the conversion of various types of estuarine natural wetlands into aquaculture ponds (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.5. The influence relationship between soil Fe-related bacterial communities, Fe, and Fe-OC\u003c/h2\u003e\u003cp\u003eRedundancy analysis (RDA) explained 39.47% and 5.05% of the variability in the FeRB community, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea). Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.579, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), Fe\u003csub\u003eo\u003c/sub\u003e (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.578, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and Fe-OC (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.485, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01) are the main factors influencing the FeRB community. Redundancy analysis (RDA) also explained 19.83% and 3.60% of the variability in the FeOB community, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb). Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.162, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) and Fe(Ⅱ) (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.123, \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05) are the main factors influencing the FeOB community.\u003c/p\u003e\u003cp\u003eThe PLS-SEM analysis of the Fe-related bacterial community, Fe, and Fe-OC (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ec) further showed that the FeRB community positively influenced Fe\u003csub\u003eo\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and Fe(Ⅱ) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). In turn, Fe(Ⅱ) negatively influenced Fe(Ⅲ) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), allowing Fe(Ⅲ) to positively influence Fe\u003csub\u003ed\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The FeOB community also had a positive effect on Fe\u003csub\u003ed\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), with Fe\u003csub\u003ed\u003c/sub\u003e subsequently positively influencing Fe\u003csub\u003eo\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Fe\u003csub\u003eo\u003c/sub\u003e further exerted a positive influence on Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), which Fe\u003csub\u003ep\u003c/sub\u003e ultimately had a direct impact on Fe-OC (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) and an indirectly effect on Fe-OC (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001) through its influence on OC:Fe (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e4.1. Impact of estuarine Wetland Conversion to Aquaculture Ponds on Fe Dynamics\u003c/h2\u003e\u003cp\u003eThe key to soil Fe cycling lies in the interconversion between Fe(Ⅱ) and Fe(Ⅲ). When natural wetlands are converted into aquaculture ponds, changes in soil properties such as soil moisture content, pH, and aeration conditions change, lead to corresponding shifts in the content of Fe(Ⅱ) and Fe(Ⅲ) (Wang et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2022b\u003c/span\u003e). In this study, we observed an overall increase in Fe(Ⅱ) and a decrease in Fe(Ⅲ) content following the conversion of natural wetlands to aquaculture ponds. The soils of aquaculture ponds are often subjected to prolonged anaerobic conditions and contain reducing sediments rich in electron donors, which can substantially enhance the reduction of Fe(Ⅲ) to Fe(Ⅱ) (Tan et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, some sampling sites showed different trends from the overall pattern after the conversion of natural wetlands. Specifically, in the \u003cem\u003ePhragmites australis\u003c/em\u003e wetland at the Minjiang Estuary and the \u003cem\u003eAegiceras corniculatum\u003c/em\u003e Wetland at the Jiulong River Estuary, Fe(Ⅱ) content exhibited an opposite pattern. This may be due to differences in radial oxygen loss (ROL) from the roots of different wetland vegetation types (Pi et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Cheng et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The adsorption and utilization of Fe(Ⅱ) by plants mainly come from the iron films on their surfaces, which are primarily composed of Fe oxides (St-Cyr and Crowder, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). In natural wetlands, plants with weaker root ROL introduced more anaerobic microsites in the rhizosphere, leading to increased Fe(Ⅱ) content and promoting the formation of thicker iron films on the plant surfaces (Chen et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Neubauer et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). After conversion to aquaculture ponds, although the redox conditions of such vegetated wetland soils do not significantly decrease, the absence of plants disrupts the plant-mediated Fe cycling, ultimately leading to reduced Fe(Ⅱ) content.\u003c/p\u003e\u003cp\u003eAfter natural wetlands are reclaimed to aquaculture ponds, soil properties change from periodic drainage to long-term flooding, resulting in a decrease in soil redox potential ( Hu et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003eb) and an increase in reductive sediments. Studies have shown that Fe\u003csub\u003ep\u003c/sub\u003e can bind with soil humic substances, promoting the formation of Fe-OC complexes (Huang et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Huang et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Correlation analysis in this study also showed a significant positive correlation between Fe\u003csub\u003ep\u003c/sub\u003e and Fe-OC (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Therefore, the observed decline in Fe\u003csub\u003ep\u003c/sub\u003e after wetland conversion is likely attributable to a concurrent reduction in soil organic matter which limits the availability of organic ligands necessary for complexation(Lin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In addition, the decrease in redox potential also promotes the preferential reduction of Fe\u003csub\u003eo\u003c/sub\u003e, which are structurally less stable and more soluble (Thompson et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Consequently, after the conversion of natural wetlands to aquaculture ponds, the Fe activation index of Fe oxides decreases (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), the Fe crystalline ratio increases (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the Fe complexing index decreases. Due to site-specific differences in soil physicochemical properties and vegetation traits, the extent and direction of Fe redox transformations vary after land use change, ultimately resulting in differences in the changes of various Fe oxides (Neubauer et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Saaltink et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e4.2. The impact of wetland conversion to aquaculture ponds on Fe-OC\u003c/h2\u003e\u003cp\u003eCorrelation analysis in the study indicates that soil Fe-OC is mainly positively regulated by factors such as Fe\u003csub\u003ed\u003c/sub\u003e, Fe\u003csub\u003eo\u003c/sub\u003e, Fe\u003csub\u003ep\u003c/sub\u003e, Fe activation index, and Fe complexing index, and negatively regulated by Fe crystalline ratio. Periodic flooding in natural wetlands causes frequent redox changes of soil Fe, and abundant plants and litter provide a large amount of organic carbon sources, creating favorable conditions for the formation of Fe-OC (Chi et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wissing et al., \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). However, after conversion to aquaculture ponds, the reductive conditions become excessively rich ( Hu et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003eb), leading to a lack of electron acceptors in the soil, an increase in reduced Fe content, a significant decrease in various Fe oxides, and a corresponding significant reduction in Fe-OC (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Studies show that soil Fe(Ⅱ) can undergo isotope exchange with Fe(Ⅲ) on the surface of Fe oxides, promoting structural rearrangement within Fe oxides, causing Fe\u003csub\u003eo\u003c/sub\u003e to transform into crystalline Fe oxides (Liu et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Pizarro et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Crystalline Fe oxides indicate a lack of active sites and are less likely to bind with organic carbon compared to Fe\u003csub\u003eo\u003c/sub\u003e (Tian and Lu, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Additionally, under anaerobic conditions, Fe\u003csub\u003eo\u003c/sub\u003e are easily reduced, leading to the release of Fe-OC contained within (Wang et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), thereby exacerbating the loss of Fe-OC after soil use change. Under oxidizing conditions, Fe-OC formed by Fe\u003csub\u003eo\u003c/sub\u003e through physical adsorption or chemical bonding is more stable, but this Fe-OC is prone to dissolution and loss under reducing conditions (Wang et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Under reducing conditions, Fe-OC formed by Fe\u003csub\u003ep\u003c/sub\u003e and organic carbon through coordination bonds or hydrogen bonds is more stable (Herndon et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), which is consistent with the correlation analysis results in this study. When the soil is converted to more strongly reducing aquaculture ponds, a significant correlation between Fe-OC, Fe\u003csub\u003ep\u003c/sub\u003e, and Fe complexing index is observed.\u003c/p\u003e\u003cp\u003eWhen the soil OC:Fe ratio is less than 1, Fe oxides mainly combines with organic carbon through adsorption. When the OC:Fe ratio is greater than 6, the two mainly combine through co-precipitation (Wang et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Therefore, in natural wetlands and aquaculture pond soils, Fe oxides mostly combines with organic carbon through adsorption. As a result, after land use changes, Fe-OC in various wetland soils generally experiences significant loss, with the most obvious loss occurring in \u003cem\u003eKandelia candel\u003c/em\u003e Wetlands (loss in the lower soil layer reaching 187.95%). This phenomenon primarily arises because \u003cem\u003eKandelia obovata\u003c/em\u003e exhibits higher ROL from its roots, leading to sufficient oxidizing conditions in wetland soils, where Fe-OC formation is predominantly based on Fe\u003csub\u003eo\u003c/sub\u003e. After conversion to aquaculture ponds, the soil shifts to a strongly reduced state, favoring Fe\u003csub\u003ep\u003c/sub\u003e as the primary component of Fe-OC. However, land-use conversion results in significant loss of soil organic matter (Herndon et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Lin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), causing a concomitant decline in Fe\u003csub\u003ep\u003c/sub\u003e content, which is tightly bound to humic acids and other organic substances. Among various wetlands, the reduction in Fe\u003csub\u003ep\u003c/sub\u003e is most pronounced in \u003cem\u003eKandelia obovata\u003c/em\u003e wetlands converted to aquaculture ponds, particularly in the ​upper soil layer​.When natural wetlands are converted into aquaculture ponds, a large amount of organic carbon is lost, but the change in Fe oxides content is more stable compared to the loss of organic carbon (Sun et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Under these conditions, the OC:Fe significantly decreases (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the proportion of Fe-OC in total organic carbon does not significantly decline. In addition, the reduction in redox potential leads to the reduction of Fe oxides, causing the loss of Fe\u003csub\u003eo\u003c/sub\u003e, which has more sites binding organic carbon, thereby exacerbating the decreasing trend of OC:Fe (Pizarro et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e4.3. Effect of Fe-related bacteria communities on Fe-OC and suggestions for carbon restoration\u003c/h2\u003e\u003cp\u003eFe-related bacteria are a group of microorganisms that are extremely sensitive to soil redox potential. After natural wetlands are converted into aquaculture ponds, the decrease in redox potential leads to significant changes in the Fe-related bacteria community (Yang et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), which is consistent with the results in this study. However, the process of converting natural wetlands into aquaculture ponds not only involves a decrease in redox potential, but also related to the changes in soil physicochemical properties, such as pH and moisture content (Lin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Studies have shown that soils with lower pH are more conducive to the growth of FeRB (H\u0026ouml;gfors-R\u0026ouml;nnholm et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e), and soils with high moisture content also promote the growth of FeRB due to their sufficient reducing conditions, (Zecchin et al., \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Compared to the \u003cem\u003eKandelia candel\u003c/em\u003e Wetland, the \u003cem\u003ePhragmites australis\u003c/em\u003e wetland and the \u003cem\u003eAegiceras corniculatum\u003c/em\u003e wetland experienced a greater reduction in soil acidity and a significant decrease in moisture content after conversion to aquaculture ponds, which lead to a trend of decreased FeRB community diversity after conversion. In natural wetlands, radial oxygen loss (ROL) from plant roots results in less Fe(Ⅱ) in the soil (S\u0026aacute;nchez-Olivares et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), and FeOB have low diversity due to a lack of electron donors. After conversion to aquaculture ponds, Fe(Ⅱ) significantly increased, which might be the reason of the increase of soil FeOB diversity. However, the root structure of \u003cem\u003eAegiceras corniculatum\u003c/em\u003e is simpler compared to \u003cem\u003ePhragmites australis\u003c/em\u003e and \u003cem\u003eKandelia candel\u003c/em\u003e, with weaker root ROL (Cheng et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and more Fe(Ⅱ). After conversion to aquaculture ponds, soil oxidation decreases while Fe(Ⅱ) decreased, leading to a significant decline in FeOB community diversity in the \u003cem\u003eAegiceras corniculatum\u003c/em\u003e wetland.\u003c/p\u003e\u003cp\u003eFe\u003csub\u003ep\u003c/sub\u003e and Fe\u003csub\u003eo\u003c/sub\u003e are important components in the formation of Fe-OC. In anaerobic environments, Fe\u003csub\u003ep\u003c/sub\u003e, as a key source of Fe(Ⅲ), directly contacts the reducing substances secreted by FeRB, leading to its reduction to Fe(Ⅱ) (Herndon et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Ortiz-Castillo et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Due to its high specific surface area and solubility on the surface, Fe\u003csub\u003eo\u003c/sub\u003e serves as an ideal electron acceptor for FeRB (Martinez et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). During the reduction of Fe\u003csub\u003ep\u003c/sub\u003e and Fe\u003csub\u003eo\u003c/sub\u003e, Fe-OC would be released (Wang et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), which leads to FeRB being mainly regulated by Fe\u003csub\u003eo\u003c/sub\u003e, Fe\u003csub\u003ep\u003c/sub\u003e, and Fe-OC (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Fe\u003csub\u003ep\u003c/sub\u003e often binds with organic matter, and this binding form promotes Fe dissolution, thereby providing more Fe(Ⅱ) substrates for FeOB. The content of Fe(Ⅱ) substrates is a key factor regulating FeOB (Riedel et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2013\u003c/span\u003e), and the results of this study partially confirm this point.\u003c/p\u003e\u003cp\u003eThe mutual adaptation between Fe-related bacterial communities and Fe environments plays a critical role in maintaining the stability of carbon pools in estuarine natural wetlands (Dubinsky et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). However, after conversion to aquaculture ponds, prolonged anaerobic soil conditions, substantial loss of SOC, and the absence of vegetation roots leading to soil compaction further exacerbate the reduced state of the soil. These changes are accompanied by marked shifts in Fe-related bacterial communities (Xiao et al., \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), promoting Fe reduction alongside Fe\u003csub\u003ep\u003c/sub\u003e depletion and Fe\u003csub\u003eo\u003c/sub\u003e crystallization (with Fe crystalline ratio increase magnitudes in both ​upper soil layer​ and ​lower soil layer​ exceeding 100%) (Khandakar et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Lin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). OC:Fe decreases due to SOC loss and reduced Fe oxides, ultimately leading to Fe-OC depletion. Thus, post-conversion strategies such as revegetation (prioritizing plants with high root ROL), could enhance soil SOC, improve soil aeration and oxidizing conditions, regulate Fe-related bacterial communities, and promote Fe oxidation. This would increase the availability of Fe\u003csub\u003eo\u003c/sub\u003e and Fe\u003csub\u003ep\u003c/sub\u003e for binding with organic carbon, restore Fe-OC pool, and achieve long-term stabilization and enhancement of soil carbon sinks.\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis study revealed that the conversion of estuarine natural wetlands into aquaculture ponds induced significant changes in the soil Fe-related bacterial community, and the interaction between Fe and carbon undergo significant changes. After the soil use change, soil Fe-OC content and OC:Fe ratio significantly decreased, accompanied by reduction in Fe activation index and Fe complexing index, and a marked increase in the Fe crystalline ratio significantly. However, these changes vary depending on wetland characteristics, such as ROL from roots and physicochemical properties, resulting in site-specific differences in the extent of of Fe-OC and OC:Fe depletion. Notably, the conversion of \u003cem\u003eKandelia candel\u003c/em\u003e wetlands led to the greatest losses, with Fe-OC in the lower soil layer declining by 187.95% and OC:Fe in the upper layer decreasing by 80.90%. Soil Fe\u003csub\u003eo\u003c/sub\u003e, Fe\u003csub\u003ep\u003c/sub\u003e, and Fe-OC are driving factors regulating Fe-reducing bacterial communities, while Fe-related bacteria, in turn, mediate the transformation of various Fe oxides by influencing the Fe cycling process. Fe oxides (mainly Fe\u003csub\u003eo\u003c/sub\u003e and Fe\u003csub\u003ep\u003c/sub\u003e) influenced Fe-OC formation directly or indirectly by modulating OC:Fe ratios. In natural wetlands, Fe-OC is strongly correlated with Fe\u003csub\u003eo\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001), whereas in aquaculture ponds, Fe-OC also shows a significant correlation with Fe\u003csub\u003ep\u003c/sub\u003e (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01), suggesting a shift in Fe-OC formation pathways under reducing conditions. Overall, the conversion of estuarine natural wetlands to aquaculture ponds alters Fe-related bacterial communities, enhances Fe reduction, Fe\u003csub\u003ep\u003c/sub\u003e depletion, and Fe\u003csub\u003eo\u003c/sub\u003e crystallization, ultimately driving Fe-OC loss. Restoration strategies, such as reintroducing vegetation with high root ROL, are critical for mitigating Fe oxide depletion, reversing crystallization, and stabilizing soil carbon pools in estuarine wetlands.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by the National Key R\u0026amp;D Program of China (2023YFE0113100) and the National Natural Science Foundation of China (42141014).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJunpeng Li:\u003c/strong\u003e Writing-original draft, Visualization, Conceptualization, Software, Data curation. \u003cstrong\u003eQingsong Zeng:\u003c/strong\u003e Visualization, Formal analysis, Conceptualization.\u003cstrong\u003e\u0026nbsp;Shuling Tang:\u0026nbsp;\u003c/strong\u003eWriting-review and editing.\u003cstrong\u003e\u0026nbsp;Yingzi Wu:\u0026nbsp;\u003c/strong\u003eWriting-review and editing. \u003cstrong\u003eYi Zheng:\u0026nbsp;\u003c/strong\u003eWriting-review and editing, Methodology. \u003cstrong\u003eWeiqi Wang:\u003c/strong\u003e Writing-review and editing, Methodology, Resources, Project administration, Validation, Funding acquisition. \u003cstrong\u003ePeipei Xue:\u0026nbsp;\u003c/strong\u003eWriting-review and editing, Methodology. \u003cstrong\u003eJordi Sardans:\u003c/strong\u003e Writing-review and editing, Investigation, Supervision. \u003cstrong\u003eJosep Pe\u0026ntilde;uelas:\u003c/strong\u003e Writing-review and editing, Investigation, Supervision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declared that there is no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAzadi, A., Baghernejad, M., Gholami, A., Shakeri, S., 2021. 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Analysis of soil chronosequence studies using reflectance spectroscopy. International Journal of Remote Sensing 37, 1881\u0026ndash;1901. https://doi.org/10.1080/01431161.2016.1163751\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"plant-and-soil","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"plso","sideBox":"Learn more about [Plant and Soil](https://www.springer.com/journal/11104)","snPcode":"11104","submissionUrl":"https://submission.nature.com/new-submission/11104/3","title":"Plant and Soil","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Iron, Fe-bound organic carbon, Fe-oxidizing bacteria, Fe-reducing bacteria, Aquaculture ponds, Estuarine wetlands","lastPublishedDoi":"10.21203/rs.3.rs-7067479/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7067479/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEstuarine wetlands are critical organic carbon sinks, where Fe oxides bind with organic carbon to form Fe-bound organic carbon (Fe-OC), which plays an important role in carbon sequestration within these ecosystems. The conversion of natural estuarine wetlands into aquaculture ponds leads to notable changes in both the Fe content and the Fe-OC pool. This study analyzed three typical Chinese estuarine wetlands to investigate changes in Fe fractions and Fe-OC during aquaculture pond conversion, employing 16S rDNA sequencing to examine Fe-related bacterial communities (Fe-oxidizing bacteria and Fe-reducing bacteria) dynamics, thereby revealing interactions between these bacteria, soil Fe, and Fe-OC throughout the transformation process. The results showed that after land-use change, Fe-OC and the molar OC:Fe rations (OC:Fe) in all soil layers decreased significantly by over 54% and 49%, respectively, while the Fe crystalline ratio (the ratio of crystalline Fe oxides to free Fe oxide) increased significantly by more than 100% across all layers. Among the Fe fractions, amorphous Fe oxides (Fe\u003csub\u003eo\u003c/sub\u003e), complexed Fe oxides (Fe\u003csub\u003ep\u003c/sub\u003e), and Fe-OC were key factors regulating Fe-reducing bacteria (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01). In turn, those Fe-related bacteria affected the Fe cycle and the transformation of Fe oxides (mainly Fe\u003csub\u003eo\u003c/sub\u003e and Fe\u003csub\u003ep\u003c/sub\u003e), thereby influencing Fe-OC and OC:Fe. The transformation process leads to Fe reduction, Fe\u003csub\u003ep\u003c/sub\u003e depletion, and Fe\u003csub\u003eo\u003c/sub\u003e crystallization, resulting in the loss of Fe-OC. To safeguard the carbon storage function of estuarine wetlands, it is essential to minimize wetland exploitation and implement strategies to curb Fe oxide loss and crystallization, thereby enhancing the stability of these critical carbon pools.\u003c/p\u003e","manuscriptTitle":"Coupled shifts in microbial and mineralogical Fe cycling destabilize organic carbon in converted estuarine wetlands","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-14 17:13:09","doi":"10.21203/rs.3.rs-7067479/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revisions","date":"2025-08-31T07:18:23+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-07-10T12:37:01+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-10T12:05:36+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Plant and Soil","date":"2025-07-09T11:46:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-09T11:44:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"Plant and Soil","date":"2025-07-07T12:28:27+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"plant-and-soil","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"plso","sideBox":"Learn more about [Plant and Soil](https://www.springer.com/journal/11104)","snPcode":"11104","submissionUrl":"https://submission.nature.com/new-submission/11104/3","title":"Plant and Soil","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"8fe531f2-e4e3-4fb8-abc8-b51ee7e1740d","owner":[],"postedDate":"July 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-08T16:02:28+00:00","versionOfRecord":{"articleIdentity":"rs-7067479","link":"https://doi.org/10.1007/s11104-025-08162-3","journal":{"identity":"plant-and-soil","isVorOnly":false,"title":"Plant and Soil"},"publishedOn":"2025-12-05 15:57:59","publishedOnDateReadable":"December 5th, 2025"},"versionCreatedAt":"2025-07-14 17:13:09","video":"","vorDoi":"10.1007/s11104-025-08162-3","vorDoiUrl":"https://doi.org/10.1007/s11104-025-08162-3","workflowStages":[]},"version":"v1","identity":"rs-7067479","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7067479","identity":"rs-7067479","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}