Search

[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]

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]

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 15 N than S. mariqueter, according to the results of the 15 N 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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Understanding the sensitivity of soil bacteria to environmental fluctuations can enhance the management of microbial ecosystem services in artificial mangrove wetlands. In this study, the variation in bacterial diversity and metabolic functions in different compartments (bulk soil, rhizosphere soil, and rhizoplane) of the soil and mangrove plant along the tidal elevation gradient was studied in Xiatanwei (Xiamen China) mangrove wetland park, a Kandelia obovata-dominated artificial mangrove stand. With the increase of the tidal flat elevation, the soil pH, total organic matter, and soil moisture contents decreased significantly, while the soil electric conductivity and redox potential increased significantly. The bacterial diversity in the bulk soil and the rhizosphere soil both decreased with the elevation of tidal levels. The relative abundance of the dominant phyla in the bulk and rhizosphere soils decreased with the rise of the tidal flat level. A significant rhizosphere effect was observed in the roots of K. obovata that the rhizosphere soil had higher bacterial diversity and richness than that in the bulk soil nearby. The rhizosphere soil of K. obovata at the low-tidal flat was enriched with the genera Nitrospira and Planctomycetes, which are valuable for the mangrove ecosystem. The Chao1 estimator and Shannon index of the bacterial community in the rhizoplane of K. obovata were much lower than that in the rhizosphere and bulk soils. Results of Biolog-Eco assay show that the bacterial groups in low tidal flat bulk soil had the highest ability in utilizing the carbon sources, which was indicated by the high values of average well color development and the high McIntosh index, and the utilization ability of carbon source decreased with the increase of tidal flat levels. The variation of the soil humidity and Eh jointly shaped the diversity and metabolic function of soil bacterial communities along the tidal flat elevation gradient., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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 207 Pb/ 206 Pb and 208 Pb/ 206 Pb 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., (Copyright © 2019 Elsevier B.V. All rights reserved.)