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[Display omitted] • Machine learning reveals spatiotemporal dynamics of SOC stocks in tidal marshes. • Sediment salinity and tidal range are key factors influencing SOC stocks prediction. • Invasive S. alterniflora contributes over half of SOC stocks in Yangtze Estuary. • S. alterniflora increased SOC stocks within the first 15 years of its invasion. • S. alternifloras high SOC storage capacity is not sustained in the long term. Spatial quantification of blue carbon ecosystem stocks is crucial for developing policies to mitigate climate change, especially in regions experiencing ongoing wetland disturbance from biological invasions. We integrated multiple machine learning models with the space-for-time substitution method to quantify the spatiotemporal impact of Spartina alterniflora invasion on tidal marsh sediment blue carbon (soil organic carbon – 'SOC') stocks at 100 cm depth in the Yangtze Estuary. Our results show that the invasive S. alterniflora contributed more than half of the total SOC stocks (2,056 ± 379 Gg C, 1 Gg = 106 kg) in the 27,600 ha tidal marshes of the Yangtze Estuary, which were estimated to be 1,107 ± 176 Gg C. S. alterniflora increased the SOC stocks in the Yangtze Estuary within the first 15 years, but this gain was not sustained in the long term, with a gradual decline (by 13.14 Mg C/ha) observed after 15 years of S. alterniflora growth. We found that sediment salinity, tidal range, and human accessibility were strong indicators for modeling and predicting SOC stocks, with Random Forest providing the best simulation of tidal marsh SOC stocks (R2 = 0.894, RMSE=7.646 Mg C/ha, and MAPE=9.469 %). Our study provides much needed information on blue carbon stocks in the Yangtze Estuary under biological invasion stress, and offers guidance for targeted S. alterniflora management actions in the future. [ABSTRACT FROM AUTHOR]

Effective seed dispersal is critical for enabling rapid state shift from a bare tidal flat to a vegetated marsh. While tidal currents are the main dispersal vector in coastal environments, biological characteristics that keep seeds afloat have been shown to influence primary seed dispersal, i.e., seed departure from the parent plant. In contrast, secondary seed dispersal processes that move (germinated) seeds trapped within microsites have been largely neglected. Here, we explore the extent to which the coupling between biotic traits and abiotic factors affects secondary seed dispersal, and whether secondary seed dispersal may explain sudden saltmarsh establishment (i.e., rapid colonization of bare tidal flat by large numbers of seedlings in spring). We used two widely spread pioneer species: Scripus mariqueter and Spartina alterniflora. Combined flume and field results demonstrated that: (1) germination stage, current velocity, and sedimentary regime have a marked effect on the probability of secondary seed dispersal by influencing the threshold lift‐off velocity of (germinated) seeds within microsites; (2) density and bud length are critical biotic traits that best predict the potential of secondary‐dispersal onset after seed germination; (3) S. alterniflora possess a stronger secondary dispersal ability compared to S. mariqueter; and (4) secondary dispersal of germinated seeds in spring may explain observed sudden marsh establishment on bare tidal flats. Our findings provide novel insight relevant to understanding the drivers of seed dispersal and thereby sudden saltmarsh establishment events, with important implications for understanding the effects of climate change on critical state transitions and enabling human‐aided restoration. [ABSTRACT FROM AUTHOR]

Typhoons pose threats to coastal wetlands, but the impacts on carbon stocks remain unclear. This study investigated typhoon effects on salt marsh carbon pools with different vegetation covers (harvested Spartina alterniflora , native Scirpus mariqueter , bare mudflat) in the Yangtze River estuary. During Typhoon Muifa (September 2022), significant erosion occurred in the Scirpus area while the harvested Spartina area experienced sediment deposition, indicating its stronger coastal protection capacity. Grain size analysis validated the geomorphic changes. The harvested Spartina area also captured coarser sediments from the mudflat. Wave data showed the amplified hydrodynamics during typhoons can transport more sediment into marshes. In the Scirpus area, surface sediments (0–15 cm) lost 43% organic carbon and 73% belowground biomass due to erosion. The deposited sediments after typhoons lacked the original high carbon content. In contrast, harvested Spartina areas maintained carbon levels despite intense hydrodynamics. The bare mudflat lost 43% total carbon after experiencing substantial erosion. This study demonstrates harvested Spartina areas effectively mitigated carbon loss and even facilitated carbon sequestration through enhanced sediment trapping during typhoons. With intensifying storm surges, seasonal harvesting of Spartina could balance coastal protection and ecological functions better than complete removal. The carbon sink capacity of sediments with native vegetation is vulnerable to typhoons due to limited resilience. Harnessing bio-geomorphic feedbacks is crucial for preserving blue carbon storage facing climate change. • Sediment sampling and UAV were combined to detect the impact of typhoon on morphological and carbon stock changes in salt marsh. • Harvested Spartina outperformed native Scirpus under storm surges for sedimentation and carbon preservation. • Harvested Spartina can enhance salt marsh carbon sequestration through bio-geomorphic feedbacks. • Salt marshes sensitive to erosion may exacerbate carbon loss during storm surge. • Seasonal Spartina harvesting can balance coastal protection and other ecological roles. [ABSTRACT FROM AUTHOR]

Invasive Spartina alterniflora has become a global management challenge in coastal wetlands. China has decided to eradicate it completely, but the high costs and its provision of beneficial ecosystem functions (EF, in the form of blue carbon and coastal protection) have raised concerns about its removal. Here, using the Yangtze Estuary as a case study, we explore a reasonable pathway of S. alterniflora management that balanced control of invasive species and EF. We simulated the spatial patterns of two key EF – blue carbon storage and wave attenuation – and identified appropriate zones for eradicating S. alterniflora based on their trade-offs. We observed contrasting patterns along the land-sea gradient for S. alterniflora community, with a decrease in blue carbon storage and an increase in wave attenuation. Notably, pioneer S. alterniflora near the foreshore displayed a high cluster of blue carbon storage (63.61 ± 7.33 Mg C ha−1) and dissipated nearly 70% of wave energy by a width of 163 m. The trade-offs between the two EF indicated that the eradication project should be implemented along the seawall rather than the foreshore. Even in the scenario of prioritized shore defense with the largest eradication zone, S. alterniflora still stored 43.1% more carbon (10.67 Gg C) compared to complete eradication and dissipated over 70% of wave energy in extreme events. Our study innovatively integrates eradication and reservation in S. alterniflora management, providing a sustainable and flexible spatial strategy that meets the needs of stakeholders. • Quantified coastal ecosystem functions with complex processes from space. • Invasive Spartina significantly enhances ecosystem functions in the foreshore. • Eradication project of Spartina should be implemented towards landward side. • Setting optimal Spartina zone width enhances coastal wetlands' ecosystem function. • Wise management of Spartina with eradication and reservation. [ABSTRACT FROM AUTHOR]

Abstract Iron plaque (IP) plays an important role in the absorption of heavy metals (HMs) and nutrients in wetland plants. The present study aims to investigate the effect of IP in Spartina alterniflora on the immobilization of wastewater borne HMs and nutrients. The physiological responses and effect of IP formation on the uptake of HMs, nitrogen (N), and phosphorus (P) were studied in S. alterniflora subjected to different synthetic wastewater (SW) levels and waterlogging durations. Results showed that IP formed in roots of S. alterniflora increased significantly with increasing SW concentration but decreased under prolonged waterlogging. Increasing the waterlogging time enhanced the alcohol dehydrogenase activity and the ethylene content in the roots of S. alterniflora. HMs including Cu, Pb, and Cr, did not significantly accumulate in the IP, despite that the IP content increased with the increasing of SW levels. The SEM–EDX analysis revealed that IP formed on the surface of S. alterniflora did absorb HMs such as Cu, Zn, and Cr. At a fixed level of SW, the amount of HMs that accumulated in the DCB extract was substantially proportional to the IP concentration in the root. Increasing of the SW level enhanced the accumulation of P in the leaves and roots of S. alterniflora. In conclusion, IP formed on S. alterniflora helped immobilize SW pollutants, including HMs and P, and the formation of IP and its effect on pollutant immobilization were influenced by the waterlogging conditions. Highlights • High level synthetic wastewater increased the iron plaque (IP) formation. • Formation of root IP decreased with the extension of waterlogging time. • Alcohol dehydrogenase activity enhanced by long time of waterlogging. • The root ethylene content increased with the prolonged waterlogging time. • Heavy metals accumulated in DCB extract was proportional to IP content. [ABSTRACT FROM AUTHOR]

The exotic Spartina alterniflora , which is native to North America, has rapidly invaded the entire eastern coast of China in recent decades. It is not clear whether elevated salinity and inundation associated with accelerated sea-level rises and saltwater intrusion will further increase the already dramatic rates of plant invasions in the future. In this study, we conducted controlled experiments to quantify the independent impacts of flooding salinity, flooding depth, and flooding frequency on the invasive S. alterniflora , as well as on the native Phragmites australis and Scirpus mariqueter in the Yangtze River Estuary, China. The results showed that increasing flooding salinity significantly decreased the height, survival rates, number of new ramets, seed setting rates, and aboveground biomass for P. australis and S. mariqueter , whereas S. alterniflora was less severely affected than the two native species. Elevated flooding depths reduced the seed setting rates for S. alterniflora , but greatly increased the survival rates, number of new ramets, and aboveground biomass. Elevated flooding frequencies decreased the height of S. alterniflora , but promoted the generation of new ramets. In contrast, P. australis tended to have stronger negative responses to increased flooding depths and frequencies than S. alterniflora . The height and aboveground biomass of S. mariqueter also decreased significantly with the increase of flooding depths, whereas no significant decreases were observed for S. mariqueter among flooding frequency levels. Specifically, both asexual and sexual reproduction for P. australis were significantly inhibited by the foregoing experimental conditions, while S. alterniflora still had sustainable competitive advantages by either or both forms of reproduction. These findings suggest that S. alterniflora was more tolerant than native P. australis and S. mariqueter , which may facilitate the spread of invasive S. alterniflora in future scenarios of increased sea-level and saltwater intrusion, or even lead to the local extinction of the endangered S. mariqueter community. [ABSTRACT FROM AUTHOR]

Tidal flat elevation in the estuarine wetland determines the tidal flooding time and flooding frequency, which will inevitably affect the formation of iron plaque and accumulations of heavy metals (HMs) in wetland plants. The present study investigated the formation of iron plaque and HM's (copper, zinc, lead, and chromium) accumulation in S. alterniflora , a typical estuarine wetland species, at different tidal flat elevations (low, middle and high) in filed and at different time (3, 6, 9, 12 h per day) of waterlogging treatment in greenhouse conditions. Results showed that the accumulation of copper, zinc, lead, and chromium in S. alterniflora was proportional to the exchangeable fraction of these metals in the sediments, which generally increased with the increase of waterlogging time, whereas the formations of iron plaque in roots decreased with the increase of waterlogging time. Under field conditions, the uptake of copper and zinc in the different parts of the plants generally increased with the tidal levels despite the decrease in the metals’ exchangeable fraction with increasing tidal levels. The formation of iron plaque was found to be highest in the middle tidal positions and significantly lower in low and high tidal positions. Longer waterlogging time increased the metals’ accumulation but decreased the formation of iron plaque in S. alterniflora . The binding of metal ions on iron plaque helped impede the uptake and accumulation of copper and chromium in S. alterniflora . [ABSTRACT FROM AUTHOR]

The frequency and duration of tidal flooding significantly influence the bioavailability of heavy metals (HMs) in sediment and hence exert toxicological effects on coastal wetland plants. In this study, the combined effects of different water inundation times (3, 6, 9, and 12 h) and HMs (Cu, Zn, Pb, and Cr) on the photosynthesis and physiology of Spartina alterniflora were investigated under greenhouse conditions. Results showed that S. alterniflora was somehow tolerant to the combined HMs treatments, and only the highest level of HM treatment decreased leaf chlorophyll content. Furthermore, the plants did not show any signs of victimization. Different times of water inundation with HMs did not exert any significant effect on the malonaldehyde (MDA) and chlorophyll contents in the leaves of S. alterniflora at day 20. Prolonged water inundation time at day 60 significantly reduced leaf chlorophyll content with the decrease in leaf photosynthetic rate, which was accompanied by a significant increase in the intercellular concentration of CO 2 . At day 60, abscisic acid dose-dependently increased along the different water inundation times, indicating that this phytohormone is involved in plant responses to flooding stress. Peroxidase (POD), superoxide dismutase (SOD), and ascorbate peroxidase (APX), showed different responses to the combined treatment of water inundation and HMs at different times. At day 20, the long duration of water inundation and HMs treatments (9 h+HMs and/or 12 h+HMs) significantly increased enzyme activity in the leaves compared with the control group (6 h). At day 60, the POD and SOD activities in the leaves of S. alterniflora decreased with prolonged water inundation time, and root APX activity significantly decreased compared with the 6 h water inundation treatment. [ABSTRACT FROM AUTHOR]

Abstract: We compared reproductive characteristics of Scirpus mariqueter and Spartina alterniflora in monocultures and mixed communities to assess the importance of clonality in the population distribution and colonization of the two species. In the core S. alterniflora zone, individuals were taller and there were fewer underground tillers than in the Spartina–Scirpus zone. Every sexual S. alterniflora individual produced about two underground tillers in the S. alterniflora zone, which was two thirds as many as in the Spartina–Scirpus zone. In contrast, the height of sexual S. mariqueter was the highest in the mixed zone, whereas the numbers of flowering individuals and vegetative individuals were the highest in the core and the Scirpus–tidal flat zones, respectively. In the Scirpus–tidal flat zone each sexual individual produced 14 vegetative individuals, which was 23 times that produced in the mixed zone, and 45 times that in the core zone. Aboveground biomass and density of sexual individuals decreased from the core to the Scirpus–tidal flat zone. The ratio of aboveground to belowground biomass was lower in core zones of the two species than in their mixed zones. From the S. alterniflora to the tidal flat zone there was a decrease in salinity and redox potential and an increase in soil moisture. [Copyright &y& Elsevier]

With the increase in coastal hazards induced by global change, estuarine deltas are urgently required to enhance nature-based coastal defenses. This study sets an example at the Nanhui nearshore salt marshes in the Yangtze Estuary, China, with a one-dimension wave attenuation empirical model and Landscape Resistance Index (LRI). We explored wave attenuation by salt marshes at site and transect scale, and put forward potential approaches to improve coastal defenses. Results showed that 1) the two 10 m-wide stripes of typical vegetation (Spartina alterniflora and Scirpus mariqueter) could attenuate wave height mostly when incident wave height was 0.22 m and 0.20 m, respectively; 2) under the condition of 0.6 m initial wave height, wave attenuation rate among all transects ranged from 32.50% to 98.30% (71.30 ± 16.09% on average); and 3) Land cover-Position-Length weighted LRI was an effective indicator for the relationship between wave attenuation and landscape pattern. Wave attenuation by salt marshes differ in various environments and are species specific. Wave attenuation along transects was also affected by both land cover and spatial configuration. Thus, we proposed some salt marsh restoration strategies, such as preferential restoration of long transects, differentiation of vegetation configuration, and engineering protections like low levees or breakwaters in front of salt marsh edges. These findings could be used to promote ecological functions in the Yangtze Estuary and other coastal marshes in the world. [Display omitted] • Wave attenuation by vegetation was species-specific and varied with environments. • Landscape Resistance Index was an effective indicator for wave attenuation by salt marshes. • Wave attenuation was influenced by both land cover and spatial configuration. • Transect landscape pattern should be considered in nature-based coastal defense. [ABSTRACT FROM AUTHOR]

Expansion of Spartina alterniflora salt marshes in the East China Sea coast is changing the ecosystem and thus, uncertainty has hampered methane (CH 4) flux accounts in these areas. To analyse seasonal and diurnal patterns of the CH 4 fluxes and their relationship with environmental factors, four plots were established in a salt marsh of the Nanhui coast in the southern fringe of the Yangtze River estuary, differing in sediment salinity and vegetation history and including one bare mudflat. Monthly studies from March 2017 to January 2018 using a chamber technique showed that CH 4 fluxes from the plots ranged from −1.7 to 72.2 mg m−2 h−1. The mature Spartina sites showed higher CH 4 emission, peaking in the summer. In the mudflat CH 4 consumption was observed in January and the summer. The seasonal CH 4 fluxes showed positive correlation (p < 0.05) with temperature, and plant development (height of vegetation), and negative correlation (p < 0.05) with water salinity. Various diurnal cycles in the CH 4 fluxes were observed at different seasons. Average CH 4 emissions were higher during the daytime than at night, however, without significant difference. Thus, the CH 4 fluxes started to rise at noon, and the maximum CH 4 flux was observed after the ebb tide (at 18:00) during nighttime. The diurnal variation in CH 4 fluxes showed a significant correlation with season but not with temperature. [Display omitted] • The Spartina alterniflora salt marsh was a CH 4 source and the mudflat was a CH 4 sink. • Seasonal CH 4 flux showed positive correlation (p < 0.05) with temperature. • Type and age of plant community was a major factor of the CH 4 flux. • Salinity affected spatial and temporal variability of CH 4 flux. [ABSTRACT FROM AUTHOR]

The ferrous iron (Fe2+) facilitates the formation of root Fe plaque of wetland plants, but its effect on the tolerance of wetland plants to artificial sewage stress has been seldom reported. In this study, the influences of Fe2+ on the formation of Fe plaque and its effects on the tolerance of Spartina alterniflora to artificial sewage stress were investigated. The artificial sewage stress decreased the plant height and chlorophyll content and significantly increased the MDA content in leaves. The symptoms of these stresses were alleviated with increasing Fe2+ concentration accompanied by significant increase in leaf alcohol dehydrogenase activity. The increase of Fe2+ concentration significantly increased the root Fe plaque content and reduced the accumulation of toxic metals in leaves of S. alterniflora. These results support our hypothesis that the exogenous Fe2+ supply may enhance the stress resistance of S. alterniflora to artificial sewage containing heavy metals. • Fe plaque content increased with the increase of exogenous Fe2+ concentration. • Increase in the Fe plaque content significantly increased the chlorophylls content • Increase in the Fe plaque content reduced the degree of peroxidation in the leaves • The leaf Cu, Zn, Pb and Cr contents were reduced by the increase in Fe plaque. • Fe2+ treatment significantly reduced the accumulation of Pb in the roots. [ABSTRACT FROM AUTHOR]

Haloxyfop-R-methyl (haloxyfop) can efficiently control Spartina alterniflora in coastal ecosystems, but its effect on soil microbial communities is not known. In the present study, the impact of the haloxyfop on rhizosphere soil bacterial communities of S. alterniflora over the dissipation process of the herbicide has been studied in a coastal wetland. The response of the bacterial community in the rhizoplane (iron plaque) of S. alterniflora subjected to haloxyfop treatment was also investigated. Results showed that the persistence of haloxyfop in the rhizosphere soil followed an exponential decay with a half-life of 2.6–4.9 days, and almost all of the haloxyfop dissipated on Day 30. The diversity of rhizosphere soil bacteria was decreased at the early stages (Days 1, 3 & 7) and recovered at late stages (Days 15 & 30) of the haloxyfop treatment. Application of haloxyfop treatment increased the relative abundance of the genera Pseudomonas , Acinetobacter , Pontibacter , Shewanella and Aeromonas. Strains isolated from these genera can degrade herbicides efficiently, which possibly played a role in the degradation of haloxyfop. The rhizoplane bacterial diversity was reduced on Day 15 while being vastly enhanced on Day 30. Soil variables, including the electric conductivity, redox potential, and soil moisture, along with the soil haloxyfop residue, jointly shape the bacterial community in rhizosphere soil. • Haloxyfop decayed exponentially in the rhizosphere soil of S. alterniflora. • The half-life of haloxyfop in the rhizosphere soil was 2.6–4.9 days. • Soil bacterial diversity decreased significantly in short term treatment (7 days). • The soil bacterial diversity was rehabilitated with the dissipation of haloxyfop. • Haloxyfop treatment increased the abundance of herbicide degrading bacteria. [ABSTRACT FROM AUTHOR]

Although there are studies on nitrous oxide (N 2 O) fluxes in coastal salt marshes, temporal and spatial variations of this greenhouse gas are still uncertain. Especially salt marshes of the East China Sea coast covered by invasive Spartina alterniflora have shown controversial results. To analyse seasonal patterns of N 2 O fluxes and their relationship with environmental factors, three plots dominated by S. alterniflora , and differing in sediment salinity and vegetation history (P1, P2, P3), and one bare mudflat (P0) in a salt marsh of Nanhui shore in the southern fringe of Yangtze River estuary have been established. Monthly studies from March 2017 to January 2018 using a chamber technique showed that average N 2 O fluxes from all four plots ranged from −41.9 to 39.3 μg N 2 O·m−2·h−1, whereas average flux (4.2 μgN 2 O·m−2·h−1) in P1, P2 and P3 was not significantly different from that measured in P0 (1.3 μgN 2 O·m−2·h−1). There was a clear seasonal difference: in spring and summer, all the sites showed slight emission while consumption prevailed in autumn and winter. In vegetated sites this trend was more remarkable than in the bare mudflat. N 2 O flux showed positive correlation (p <.05) with air and sediment temperature, and plant development (height of vegetation). Nitrate was not the limiting factor of N 2 O emission in the Yangtze estuary. In the salt marsh where vegetation community was mature, higher sediment salinity reduced N 2 O emission (P1 < P2) by influencing other environmental factors such as total carbon (TC), total nitrogen (TN) content and sediment texture. In comparison with other tidal macrophytes S. alterniflora showed relatively low N 2 O emission. Therefore, it can be considered as a species for tidal zone stabilisation. Unlabelled Image • Spartina areas are not significant N 2 O sources being at comparatively low level with other tidal macrophytes. • Type and age of plant communities determined the temporal and spatial variability of N 2 O flux. • NO 3 − is not a limiting factor of N 2 O flux in the nitrogen-rich Yangtze estuary. • Sediment salinity affected spatial rather than temporal variability of N 2 O flux. • No significant correlation was found between N 2 O flux and TOC, TN or sediment texture. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Fe plaque content decreases significantly with the elevation of the tidal flat. • The content of Fe plaque in roots of Phragmites is higher than that of Spartina. • High soil Eh is conducive to the formation of crystalline Fe plaque. • The diversity of rhizosphere bacteria in Phragmites is higher than that in Spartina. • The rhizosphere of Phragmites at low tide flat enriches more Fe bacteria than Spartina. As two common estuarine wetland plants in China, Spartina alterniflora and Phragmites australis significantly differ in the mechanism of gas transportation and radial oxygen loss, and this difference can lead to significant differences in the shaping of the rhizosphere bacterial community and the formation of root iron (Fe) plaque. In this study, the difference in root Fe plaque formation between S. alterniflora and P. australis on the redoxcline of tidal flat was determined, and the composition of Fe-oxidizing bacteria (IOB) and Fe-reducing bacteria (IRB) communities in the rhizosphere and Fe plaque of the two plants was compared. With the increase in soil redox potential (Eh), the Fe plaque (amorphous and crystalline forms) content in the roots of S. alterniflora and P. australis decreased significantly. The Fe plaque content in the roots of P. australis was significantly higher than that of S. alterniflora , regardless of the tidal level. High soil Eh improved the formation of crystallized Fe plaque, as the proportion of crystalline Fe plaque increased significantly with the increase in soil Eh. Under similar soil Eh, the microbial diversity of the P. australis rhizosphere was higher than that of the S. alterniflora rhizosphere. The relative abundances of the dominant IOB and IRB, such as the genera Desulfuromonas , Geothermonbacter , Pseudomonas , Paracoccus , Geobacter , Amaricoccus , Pelobacter , and Gallionella , in the P. australis rhizosphere in low-tidal flat are generally higher than those in the S. alterniflora rhizosphere. However, the relative abundances of primary IRB (such as Desulfuromonas) and IOB (such as Pseudomonas) in the rhizosphere of the two plants increased with the increase in soil Eh and soil total Fe content, indicating that the enrichment of Fe bacteria in the S. alterniflora and P. australis rhizospheres may not be the primary determinant of Fe plaque formation. [ABSTRACT FROM AUTHOR]

It is well accepted that tidal wetland vegetation performs a significant amount of water filtration for wetlands. However, there is currently little information on how various wetland plants remove nitrogen (N) and phosphorus (P) and how they differ in their denitrification processes. This study compared and investigated the denitrification and phosphorus removal effects of three typical wetland plants in the Yangtze River estuary wetland (Phragmites australis , Spartina alterniflora , and Scirpus mariqueter), as well as their relevant mechanisms, using an experimental laboratory-scale horizontal subsurface flow constructed wetland (CW). The results showed that all treatment groups with plants significantly reduced N pollutants as compared to the control group without plants. In comparison to S. mariqueter (77.2–83.2%), S. alterniflora and P. australis had a similar total nitrogen (TN)removal effectiveness of nearly 95%. With a removal effectiveness of over 99% for ammonium nitrogen (NH 4 +-N), P. australis outperformed S. alterniflora (95.6–96.8%) and S. mariqueter (94.6–96.5%). The removal of nitrite nitrogen (NO 2 −-N)and nitrate nitrogen (NO 3 −-N)from wastewater was significantly enhanced by S. alterniflora compared to the other treatment groups. Across all treatment groups, the removal rate of PO 4 3--P was greater than 95%. P. australis and S. alterniflora considerably enriched more 15N than S. mariqueter , according to the results of the 15N isotope labeling experiment. While the rhizosphere and bulk sediments of S. alterniflora were enriched with more simultaneous desulfurization-denitrification bacterial genera (such as Paracoccus , Sulfurovum , and Sulfurimonas), which have denitrification functions, the rhizosphere and bulk sediments of P. australis were enriched with more ammonia-oxidizing archaea and ammonia-oxidizing bacteria. As a result, compared to the other plants, P. australis and S. alterniflora demonstrate substantially more significant ability to remove NH 4 +-N and NO 2 −-N/NO 3 −-N from simulated domestic wastewater. [Display omitted] • CWs with plants removed substantially more N than controls. • Plant groups enriched more denitrifying bacteria in plant rhizospheres than controls. • The Spartina and Phragmites groups removed much more N than the Scirpus group. • Phragmites have the highest NH 4 +_N removal rate due to enrichment of AOA and AOB. • CWs with Spartina had the highest removal rate for NO 3 −_N and NO 2 −_N. [ABSTRACT FROM AUTHOR]

Abstract The decomposition of salt marsh plants is affected by the variation of physiochemical factors caused by the change of tide level. In the present study, plant tissues of Spartina alterniflora from controlled metal exposure experiments were subjected to a field decomposition trial at different tidal levels in a tidal flat of Chongming Island, Shanghai. The contents of the metals and Pb stable isotope ratios of the plant litter and the adjacent sediment were followed. The mass loss rate of the root and leaf litters of S. alterniflora decreased with the increase of burial time. Leaf had the highest decomposition rate (0.009 day−1 to 0.020 day−1) compared to that of the roots (0.004 day−1 to 0.005 day−1) and stems (0.002 day−1 to 0.006 day−1). Leaf had the highest decomposition rate possibly due to the significantly lower C/N ratio (16.0–44.6) compared to that of the roots (32.8–88.9) and stems (43.7–120.9). The mass loss rate of the roots and leaves of S. alterniflora was higher in the high tidal marsh than that in the low tidal marsh, especially at the late stages of decomposition. The concentrations of metals in leaf litter of S. alterniflora increased, whereas the pools of metals in most of the plant litters decreased significantly with the increasing of the decomposition time. The ratios of 207Pb/206Pb and 208Pb/206Pb in the root litters decreased significantly in the first 290 days of decomposition and then increased significantly at Day 350, while the Pb isotope ratios in adjacent sediment showed no significant changes. Fast mass loss of plant litters induced the significant decrease in metals' pools at early stages of decomposition, and release of the plant tissue Pb was greatly inhibited due to the slowed mass loss at the late stages of decomposition. Graphical abstract Unlabelled Image Highlights • The mass loss rate of the root and leaf decreased with the increase of burial time. • The mass loss rate of the leaf and root was high in the high tidal marsh. • Metals' concentration increased in leaf with the increasing of decomposition time. • Pb isotope ratio in root litters decreased till the day 290 of decomposition. • Pb isotope ratios in adjacent sediment had no significant changes. [ABSTRACT FROM AUTHOR]