Management strategies of translocated pondweed Monochoria hastata and its ecological and economic impacts.

Understanding the impacts of, and options for, controlling invasive species is crucial to their management. Wetlands are a widely invaded ecosystem, since dispersal of aquatic species is facilitated by seasonal flooding. This study evaluated the effects of the translocated pondweed Monochoria hastata on fish and rice production in two wetlands of Bangladesh over six years (2017-2022). Fish and rice production were compared between control (negligible M. hastata) and three treatments under different M. hastata management methods comprising manual-, herbicide- and mechanical-treatment. Density of M. hastata increased significantly in all treatment groups over time in both wet and dry seasons. However, M. hastata density was lower by 270% in the dry season than the wet season. For fishes, a negative relationship between M. hastata density and fish production was recorded for snakeheads and catfishes, the most saleable fishes, whereas a mixed pattern was recorded for barbs and minnows across treatments. A positive relationship occurred between the density of M. hastata and production of the most common fish, mud eel, and therefore, the overall fish production increased in all treatment groups. Compared to control plots, rice production was lower in M. hastata infested plot groups. Among the M. hastata infested plot groups, rice production in herbicide-and mechanical-treatment groups was similar but lower than the manual-treatment group. Although manual-treatment plots yielded greater rice production, the weed management cost was also higher. This study provides evidence that translocated M. hastata can be of an invasive nature and impact rice production, not only by reducing yield but also by increasing the production costs through additional management for M. hastata control. Its presence in wetlands in Bangladesh can increase overall fish production due to the overriding influence of increased mud eel yield which has little demand locally but can decrease the species of high demand (e.g. snakehead and catfish). None of the existing control measures are effective in controlling M. hastata. Further research is needed on better management approaches for both agricultural and fish production in areas invaded by M. hastata.

Enhanced pollution removal from canal water by coupling aeration to floating treatment wetlands.

Floating treatment wetlands (FTWs) are natural solutions for purifying polluted water, providing a green surface area and improving city landscape. This study investigated if the efficiency of FTWs can be improved by aeration for treating contaminated canal water. The three used plant species were Canna generalis, Phragmites australis, and Cyperus alternifolius. The experiment was carried out in three FTWs with aeration and three without aeration to compare the removal for COD, NH4+-N, E. coli, PO43--P, and Fe. In the aerated FTWs, air blowers were installed to run at two different air flow rates of 2.5 L min-1 (Batch 1) and 1.0 L min-1 (Batch 2). Aeration increased the dissolved oxygen concentrations in each tank, which came over 6.5 mg L-1 in both batches. This study sheds light on the positive impact of aeration has on COD and NH4+-N removal: these are nearly three-fold higher compared to non-aeration conditions and reached approximately 99% (1.7-log reduction) for E. coli removal. Additionally, the plant growth rate in the aerated FTWs was higher than in the non-aerated ones. The average shoot growth rate of Phragmites australis was 0.76 cm d-1 for the aerated FTW which was two-fold higher compared to the non-aerated one.

This article investigates the treatment performance of Floating Treatment Wetlands (FTWs) coupled with aeration to reduce the diffuse pollution in canal water. The results showed that the aeration enhanced the treatment of organics and nutrients, and the plant growth of the aerated FTWs was two-fold higher than that of non-aerated FTWs, which has a phytoremediation potential for treating canal water in Ho Chi Minh city.

Review of hydraulic conditions optimization for constructed wetlands.

Hydraulic conditions exert a comprehensive and vital influence on constructed wetlands (CWs). However, research on this subject is relatively limited. Hydraulic parameters can be categorized into design and operational parameters based on their properties. The design parameters are represented by the hydraulic gradient, substrate porosity, and aspect ratio, while operational parameters are represented by the hydraulic retention time, hydraulic loading rate, and water depth. These parameters directly or indirectly affect the operational lifespan and pollutant removal performance of CWs. Currently, the primary measures for optimizing the hydraulic conditions of CWs involve hydraulic structure and numerical simulation optimization methods. In this review, we aimed to elucidate the impact of hydraulic conditions on CW performance and summarize current optimization strategies. By highlighting the significance of hydraulic parameters in enhancing pollutant removal and extending operational lifespan, this review provides valuable insights for improving CW design and management. The findings will be useful for researchers and practitioners seeking to optimize CW systems and advance the application of nature-based solutions for wastewater treatment.

Investigating the effect of hydraulic residence time, artificial aeration and plants presence on different constructed wetland designs treating oil industry effluent.

Constructed Wetlands (CW) have gained popularity over the last decades due to their cost-effectiveness, easy and simple operation and environmental compatibility in wastewater treatment. This ecological engineering technology appears particularly ideal for low-income regions. In this study, three widely used CW types (horizontal flow, vertical flow, and hybrid CW) were constructed and evaluated for their effectiveness in removing various pollution parameters (BOD5, COD, TSS, NH4-N, NO3-N, and TP) from an industrial effluent. Different configurations were tested such as CW type, hydraulic residence time, plants presence, and artificial aeration. Results showed that the hybrid CW configuration (i.e., vertical flow CW followed by horizontal subsurface flow CW) achieved the highest removal rates of all pollutants, i.e., more than 90% of BOD5, COD, TSS, and NH4-N. The single horizontal flow and vertical flow CW designs showed variations in the removal of NO3-N and TP (less than 30%), which were significantly improved (50% and 70%, respectively) by using the hybrid CW system. Artificial aeration significantly improves the performance of the CW system, especially for ammonia nitrogen and organic matter removal, while plants presence is also beneficial in the treatment performance. An 8-days HRT seems to be adequate for high removal rates in passive CW designs, though in aerated wetlands a lower HRT of 4 days seems sufficient. These findings suggest that the hybrid CW system could be a promising option for efficient wastewater treatment in developing regions.

[Spatial distribution of soil microorganisms in the Zoige Plateau peatland, Southwest China]. / 若尔盖高原泥炭沼泽土壤微生物空间分布.

Understanding the composition and spatial distribution patterns of microbial communities in plateau peatland soils is crucial for preserving the structural and functional stability of highland wetlands. We collected 50 soil samples from the core conservation area of Zoige peatland along horizontal and vertical distributions to analyze the soil bacterial and fungal diversity by using high-throughput sequencing technology, combined with Mantel tests and multiple regression on matrices (MRM) statistical methods, as well as the spatial distribution characteristics of community structure similarity at a local scale. The results showed that the dominant soil bacterial and fungal groups were Chloroflexi (accounting for 33.2% and 25.1% of the total bacterial community in horizontal and vertical directions, respectively) and Ascomycota (54.7% and 76.4%). The similarity of microbial community structure in both horizontal and vertical directions decreased with increasing spatial distance of the sampling points. The turnover rates of bacterial and fungal communities in the vertical direction were 8.8 and 8.6 times as those in the horizontal direction, respectively. Based on the relative abundance of the communities, we classified microbes into six groups. As the number of rare species in the community increased, the slope of community distance decay decreased. The conditionally rare or abundant taxa (CRAT) category group showed the most similar spatial distribution characteristics to the total microbial community. Mantel analysis indicated that soil organic carbon, total nitrogen, and available phosphorus were key factors driving the distribution of bacterial and fungal communities in the horizontal direction, while soil organic carbon, available carbon, pH, and soil bulk density were the main factors determining the vertical distribution. MRM analysis further showed that both soil physicochemical indicators and spatial distance significantly affected the assembly of microbial communities, where soil factors explained more about the vertical distribution of microbial communities than the horizontal distribution. The impact of soil factors on microbial community distribution was much greater than that of spatial factors through diffusion limitation. In summary, the microbial communities in the plateau peatland soils exhibited more pronounced vertical distribution differences and environmental response characteristics.

Modelling the drivers of land use and land cover change of the great Amanzule wetland ecosystem to inform the development policy of the southwestern oil-rich region of Ghana.

This study focused on the current and future drivers of land-use change and its impact on the Amanzule wetland. It suggests policy implications for reviewing and strengthening existing policies for sustainable land use. This study employed remote sensing and GIS techniques, including participatory rural appraisal techniques. The administration of questionnaires and focus group discussions were conducted in the Ellembelle and Jomoro municipalities, where the Amanzule wetland provides economic and social services. The results showed increased land use over the last 32 years driven by various drivers, including food crop production, rubber plantations, oil and gas establishments, and infrastructure development. The study further revealed that these drivers could influence land-use change in 18 years (2018-2036). Urbanisation, cropland, rubber plantations, and shrubland will drive land-use change in the study area between 2036 and 2054. The Amanzule wetland area is expected to decrease from 272.34 ha in 2018 to 210.60 ha by 2036. The wetland area is expected to further decrease from 210.60 ha in 2036 to 174.33 ha by 2054. Other land use classes, such as mangrove and swamp forests, are also expected to decrease within the same period. The study recommends advocating for a wetland policy, enforcing the Land Use and Spatial Planning Act 925 and the Petroleum Exploration and Production Act 919 for sustainable development.

Treatment of domestic wastewater and extracellular polymeric substance accumulation in siphon-type composite vertical subsurface flow constructed wetland.

In this study, the siphon-type composite vertical flow constructed wetland (Sc-VSsFCW) was constructed with anthracite and shale ceramsite chosen as the substrate bed materials. During the 90-day experiment, typical pollutant removal effects of wastewater and extracellular polymeric substance (EPS) accumulation were investigated. Meanwhile, X-ray diffraction and scanning electron microscopy were used to examine the phase composition and surface morphology to analyze adsorptive property. Additionally, we evaluated the impact of siphon effluent on clogging and depolymerization by measuring the EPS components' evolution within the system. The findings reveal that both the anthracite and shale ceramsite systems exhibit impressive removal efficiencies for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), chemical oxygen demand (COD), ammonium nitrogen (NH4 +-N), and nitrate nitrogen (NO3 --N). However, as the experiment progressed, TP removal rates in both systems gradually declined because of the saturation of adsorption sites on the substrate surfaces. Although the dissolved oxygen (DO) levels remained relatively stable throughout the experiment, pH exhibited distinct patterns, suggesting that the anthracite system relies primarily on chemical adsorption, whereas the shale ceramsite system predominantly utilizes physical adsorption. After an initial period of fluctuation, the permeability coefficient and porosity of the system gradually stabilized, and the protein and polysaccharide contents in both systems exhibited a downward trend. The study underscores that anthracite and shale ceramsite have good effectiveness in pollutant removal as substrate materials. Overall, the hydraulic conditions of the double repeated oxygen coupling siphon in the Sc-VSsFCW system contribute to enhanced re-oxygenation capacity and permeability coefficient during operation. The changes in EPS content indicate that the siphon effluent exerts a certain depolymerization effect on the EPS within the system, thereby mitigating the risk of biological clogging to a certain extent. PRACTITIONER POINTS: The system can still maintain good pollutant treatment effect in long-term operation. The re-oxygenation method of the system can achieve efficient and long-term re-oxygenation effect. The siphon effluent has a certain improvement effect on the permeability coefficient and porosity, but it cannot effectively inhibit the occurrence of clogging. The EPS content did not change significantly during the operation of the system, and there was a risk of biological clogging.

Performance and mechanisms of constructed wetland integrated microbial fuel cell for remediation and detoxification of leather tannery wastewater.

Several previous studies concerned of microbial fuel cells integrated into constructed wetlands, nevertheless, their application as a convenient treatment for wastewater is still developing. In this experimental investigation, five CW-MFC systems were similarly designed, setup, and operated in a batch mode for two subsequent cycles. Each cycle lasted for 10 days to evaluate the performance of CW-MFC system for the remediation of real leather tannery wastewater (LTW). Four CW-MFCs were planted, each with different type of vegetation including Conocarpus, Arundo donax, Canna lily, and Cyperus papyrus in CW1-MFC, CW2-MFC, CW3-MFC, and CW4-MFC, respectively. The fifth CW5-MFC was maintained unplanted and considered as the control system. The performance of each CW-MFCs systems was evaluated mainly based on the removal of organic content (COD), total dissolved solid (TDS) elimination, and power generation. The results demonstrated that the four types of plants maintained healthy and no sign of wilting was observed during the 20 days of monitoring. For the first cycle of batch operation, maximum removal efficiencies of COD were 99.8%, 99.5%, 99.7%, 99.6% and 99.5% with power outputs of 10,502.8, 10,254.6, 9956.4, 10,029.6, and 9888.0 mW/m3, while, maximum TDS elimination were 46.7%, 39.7%, 60.8%, 55.5%, and 13.8% observed in CW1-MFC, CW2-MFC, CW3-MFC, CW4-MFC, and CW5-MFC, respectively. Very comparable results were observed in the second operation cycle. Results of phototoxicity test indicated that the germination of Hordeum vulgare and Triticum aestivum were 100% watered with treated effluent compared to 90% accomplished with tap water as the control solution for both types of seeds.

Phosphorus removal in surface flow treatment wetlands for domestic wastewater treatment: Global experiences, opportunities, and challenges.

Treatment Wetlands (TWs) are widely used for the treatment of domestic wastewater, with an increasing emphasis on provision of multiple co-benefits. However, concerns remain regarding achieving stringent phosphorus (P) discharge limits, system robustness and resilience, and associated guidance on system design and operation. Typically, where P removal is intended with a passive TW, surface flow (SF) systems are the chosen design type. This study analysed long-term monitoring datasets (2-30 years) from 85 full-scale SF TWs (25 m2 to 487 ha) treating domestic sewage with the influent load ranging from 2.17 to 54,779 m3/d, including secondary treatment, tertiary treatment, and combined sewer overflows treatment. The results showed median percentage removals of total P (TP) and orthophosphate (Ortho P) of 28% and 31%, respectively. Additionally, median areal mass removal rates were 5.13 and 2.87 gP/m2/yr, respectively. For tertiary SF TWs without targeted upstream P removal, 80% of the 44 systems achieved ≤3 mg/L annual average effluent total P. Tertiary SF TWs with targeted upstream P removal demonstrated high robustness, delivering stable effluent TP < 0.35 mg/L. Seasonality in removal achieved was absent from 85% of sites, with 95% of all systems demonstrating stable annual average effluent TP concentrations for up to a 30-year period. Only two out of 32 systems showed a significant increase in effluent TP concentration after the initial year and remained stable thereafter. The impact of different liner types on water infiltration, cost, and carbon footprint were analysed to quantify the impact of these commonly cited barriers to implementation of SF TW for P removal. The use of PVC enclosed between geotextile gave the lowest additional cost and carbon footprint associated with lining SF TWs. Whilst the P-k-C* model is considered the best practice for sizing SF TWs to achieve design pollutant reductions, it should be used with caution with further studies needed to more comprehensively understand the key design parameters and relationships that determine P removal performance in order to reliably predict effluent quality.

Responses of soil fungal community composition and function to wetland degradation in the Songnen Plain, northeastern China.

Introduction: Wetlands are ecosystems that have a significant impact on ecological services and are essential for the environment. With the impacts of rapid population growth, wetland reclamation, urbanization, and land use change, wetlands have undergo severe degradation or loss. However, the response of soil fungal communities to wetland degradation remains unknown. It is crucial to comprehend how the diversity and population dynamics of soil fungi respond to varying levels of degradation and ecological progression in the wetlands of the Songnen Plain. Methods: In this study, high- throughput sequencing technology to analyze the variety and abundance of soil fungi in the undegraded (UD), light degraded (LD), moderate degraded (MD), and severe degraded (SD) conditions in the Halahai Nature Reserve of Songnen Plain. This study also explored how these fungi are related to the soil's physicochemical properties in wetlands at various degradation levels. Results: The findings indicated that Basidiomycota and Ascomycota were the primary phyla in the Songnen Plain, with Ascomycota increasing and Basidiomycota decreasing as wetland degradation progressed. Significant differences were observed in soil organic carbon (SOC), total nitrogen (TN),and soil total potassium (TK) among the succession degradation stages. With the deterioration of the wetland, there was a pattern of the Shannon and Chao1 indices increasing and then decreasing. Non-metric Multidimensional Scaling (NMDS) analysis indicated that the fungal community structures of UD and LD were quite similar, whereas MD and SD exhibited more distinct differences in their fungal community compositions. Redundancy analysis (RDA) results indicated that Soil Water content (SWC) and total nitrogen (TN) were the primary environmental factors influencing the dominant fungal phylum. According to the FUNGuild prediction, Ectomycorrhizal and plant pathogens gradually declining with wetland degradation. Discussion: In general, our findings can offer theoretical support develop effective solutions for the preservation and rehabilitation of damaged wetlands.

Inverse modeling of 2010-2022 satellite observations shows that inundation of the wet tropics drove the 2020-2022 methane surge.

Atmospheric methane concentrations rose rapidly over the past decade and surged in 2020-2022 but the causes have been unclear. We find from inverse analysis of GOSAT satellite observations that emissions from the wet tropics drove the 2010-2019 increase and the subsequent 2020-2022 surge, while emissions from northern mid-latitudes decreased. The 2020-2022 surge is principally contributed by emissions in Equatorial Asia (43%) and Africa (30%). Wetlands are the major drivers of the 2020-2022 emission increases in Africa and Equatorial Asia because of tropical inundation associated with La Niña conditions, consistent with trends in the GRACE terrestrial water storage data. In contrast, emissions from major anthropogenic emitters such as the United States, Russia, and China are relatively flat over 2010-2022. Concentrations of tropospheric OH (the main methane sink) show no long-term trend over 2010-2022 but a decrease over 2020-2022 that contributed to the methane surge.

Microplastics abundance and potential ecological risk assessment in sediment, water and fish of Deepor Beel-a Ramsar Wetland of the Brahmaputra plain, India.

Microplastics (MPs) are increasingly recognized as environmental contaminants with complex impacts on fish and other aquatic organisms. This study determined the microplastics abundance and the induced-ecological risks of microplastics in water, sediment, and commonly harvested fishes of a Ramsar site, Deepor Beel of Assam, India. Six samples of water and sediment were collected with nine individuals of two commonly harvested fish species Puntius sophore (Pool Barb) and Gudusia chapra (Indian River Shad). The abundance of microplastics in water and sediments were analyzed through organic matter digestion using hydrogen peroxide (H2O2, 30%) and sodium chloride (NaCl) for density separation. Potassium hydroxide (KOH, 10%) was used for digestion of fish gut. The microplastics were identified visually and chemically characterized through micro-Raman spectroscopy. Total 467 microplastic particles in water and sediment, and 62 particles in fish were identified. An average concentration of 0.55 ± 0.06 particles/L in water, 4.03 ± 0.41 particles/100 g in sediment samples, 3.83 ± 2.26 particles/individual in Puntius sophore, and 6.5 ± 3.40 particles/individual in Gudusia chapra were detected. Fibers accounted to the major shape of microplastic in water (54%) and sediment (50%), whereas fragments (65%) were the major shapes detected in both fishes. The color composition includes blue, black, red, green, brown, yellow, and transparent. Fiber particles size ranged between 150 and 1782 µm, fragments within 85-325 µm, and sphere within 85-220 µm. Chemical characterization of microplastics revealed polymer types including polypropylene (PP = 27%), polyvinyl chloride (PVC = 25%), acrylonitrile-butadiene-styrene (ABS = 18%), polycarbonate (PC = 13%), polyethylene (12%), and polystyrene (PS = 5%). PHI levels were at hazard level III and V for water and sediment samples and at level IV for both fish species. The PLI at hazard level I indicated low pollution levels, whereas the PERI were within danger and extreme danger levels. This study is the first report in abundances of microplastics and the ecological risk assessment of microplastics in surface waters, sediments and fishes of Deepor Beel wetland.

The fate of sulfamethoxazole in microcosms of the macrophyte Schoenoplectus californicus and its impact on microbial communities.

Sulfamethoxazole is a widely used antibiotic frequently found as an environmental pollutant. It can alter microbial communities and increase antibiotic resistance, becoming a public health risk. Constructed wetlands have the potential for removing sulfamethoxazole from polluted waters, but the role of different macrophytes in this process is not well understood. We investigated the fate of sulfamethoxazole and its effect on bacterial communities in microcosms containing Schoenoplectus californicus, an altitude-tolerant macrophyte. Within the first 10 h after introducing sulfamethoxazole (initial concentration 5 mg/L) to the microcosms, the concentration in the liquid phase significantly differed between microcosms with and without S. californicus. However, over the long term (15 and 30 days post-addition), the removal percentage (around 75%) in the liquid phase was not significantly influenced by S. californicus, indicating that sediments might be primarily responsible for removing the antibiotic. The presence of S. californicus promoted algae growth in the microcosms, and we determined that algae contributed to sulfamethoxazole removal from the liquid phase, likely through adsorption. Additionally, we characterized bacterial communities in the microcosm sediments via nanopore sequencing to identify changes following sulfamethoxazole addition. The relative abundance of Proteobacteria increased from 37-46% to 48-99% with the addition of the antibiotic. Conversely, the relative abundance of cyanobacteria decreased significantly after sulfamethoxazole was added (from 17 to 35% to less than 2%), suggesting it may serve as a biological marker for sulfamethoxazole pollution. In addition, the functional profile of the community was estimated from taxonomic diversity using PICRUST.

Quantitative assessment of the key drives shaping the long-term dynamics of geographically isolated wetlands: A case study within the Nenjiang River Basin, Northeast China.

Geographically isolated wetlands (GIWs) offer a diverse array of ecosystem services and contribute largely to landscape functions. Numerous studies have documented the substantial pressures on wetland ecosystems from both natural changes and human activities worldwide. However, the quantification of these impacts on GIWs remains scarce. This study presents an assessment of the spatiotemporal dynamics of GIWs in the downstream portion of the Nenjiang River Basin, Northeast China, over a 38-year period (1978-2015). We quantitatively evaluated the impacts of anthropogenic activities and natural changes using a five-stage wetland dataset (1978, 1990, 2000, 2008, and 2015) and four-stage (1990, 2000, 2010, and 2015) land use datasets. Our findings indicate that 86% of the GIWs in the study area have vanished, primarily replaced by unused land (28.39%) and farmland (54.90%). Anthropogenic activities were identified as the main cause of wetland loss from 1978 to 2008, whereas natural changes have played a more significant role in recent years of GIWs. Considering the ongoing regional trends of warming and drying, it is imperative to conserve and restore GIWs to maintain their ecosystem services for a broad spectrum of beneficiaries.

Consequences of intense drought on CO2 and CH4 fluxes of the reed ecosystem at Lake Neusiedl.

Reed (Phragmites australis) dominated wetlands are commonly known as strong carbon (C) sinks due to the high productivity of the reed plant and C fixation in the wetland soil. However, little is known about the effects of drought on reed-dominated wetlands and the possibility of Pannonian reed ecosystems being a source of greenhouse gases (GHG). The drought at Lake Neusiedl had a particular impact on the water level, but also had consequences for the reed belt. Therefore, we investigated the drought-influenced C fluxes and their drivers in the reed ecosystem of this subsaline lake over a period of 4.5 years (mid-2018 to 2022). We applied eddy covariance technique to continuously quantify the vertical turbulent GHG exchange between reed belt & atmosphere and used vegetation indices to account for reed growth. Methane emissions decreased by 76% from 9.2 g CH4-C m-2a-1 (2019) to 2.2 g CH4-C m-2 a-1 (2022), which can be explained by the falling water level, the associated drying out of the reed belt and its consequences. Carbon dioxide emissions initially decreased by 85% from 181 g CO2-C m-2 a-1 (2019) to 27 g CO2-C m-2 a-1 (2021), but then increased to twice the 2019 level in 2022 (391 g CO2-C m-2 a-1). Due to the drying reed belt, the reed initially grew into formerly water-covered areas within the reed belt, especially in 2021, leading to higher photosynthesis through 2021. This development stopped and even reversed in 2022 as a consequence of the sharp decrease in sediment water content from about 65 to 32 Vol-% in mid-2022. Overall, drought led to a decoupling of the reed ecosystem from the open lake area and developed the wetland into a strong C source.

Ecological networks in savannas reflect different levels of hydric stress in adjacent palm swamp forest ecosystems.

Palm swamp forests are wetland ecosystems typical of the Brazilian Cerrado, which in recent decades have undergone intense changes due to land use alterations and climate change. As a result of these disturbances, many palm swamps have been experiencing significant drying, which can also affect adjacent vegetation. In the present study, we evaluated whether the drying of palm swamps affects the structure of plant-herbivore networks located in adjacent savanna areas in Brazil. Our results show that savanna areas adjacent to dry zones of palm swamps have fewer interactions, fewer interacting species, and a less specialized topology, which corroborates our expectations. Our findings indicate that the drying of palm swamps also has propagated impacts on adjacent savanna vegetation, impairing more specialized interactions in these environments. On the other hand, contrary to expectations, plant-herbivore networks in dry zones displayed higher modularity, lower nestedness and lower robustness than those in wet zones, suggesting that in dry environments, species tend to compartmentalize their interactions, even with lower interaction specialization. This is the first study to investigate the impacts of environmental drying on the structure of plant-herbivore networks in tropical ecosystems, highlighting the complexity of these effects and their differential impact on specialized and generalized interactions. Understanding these dynamics is crucial for developing effective conservation and management strategies in the face of ongoing environmental changes.

Unraveling the synergistic promotion mechanism of Fe0 coupling phragmites australis biomass for nitrogen removal in coastal wetland: From low to moderate salinities.

The simulated coastal constructed wetlands supplemented with Fe0 and phragmites australis (P.A) biomass (CW-M) were constructed to improve nitrogen removal under different salinities (0-15‰). Results showed that the denitrification performance of CW-M were improved significantly, with the higher NO3--N removal of 72-94% and lower N2O emission flux, when compared with mono-P.A biomass(CW-bio), mono-Fe0 system (CW-Fe) and control system. The nitrogen removal showed a trend of first increasing (0‰-7‰) and then decreasing (7‰-15‰) with the highest NO3--N removal of 94% and enhanced removal efficiency of 41% in CW-M. Fe0 and P.A biomass coupling could reduce the stress of salinity on denitrification. Batch experiments have demonstrated that Fe0 and P.A biomass could mutually stimulate more total organic carbon and total iron (TFe) release as electron donors for denitrification. Meanwhile, appropriate salinity could also promote the release of TFe. The typical heterotrophic denitrifying genera Bacillus and iron autotrophic denitrifying genera Thermomonas have the highest proportion in CW-M, with 21.83% and 0.10%, respectively. Fe0 and P.A biomass adding simultaneously promoted the carbon and iron metabolism, further enhancing the nitrogen metabolism process. The joint enhancement of autotrophic and heterotrophic denitrification contributes to NO3--N removal in CW-M for treating saline, low C/N wastewater in coastal wetlands.

Nitrogen inputs promote wetland carbon dioxide and nitrous oxide emissions in China: a meta-analysis.

Nitrogen is the most limiting nutrient in wetland ecosystems. Changing in nitrogen nutrient status has a great effect on wetland carbon and nitrogen cycling. However, there is much uncertainty as to wetland greenhouse gas emissions response to nitrogen inputs in China. In this study, we synthesized 177 paired observations from 27 studies of greenhouse gases emissions related to nitrogen additions across wetland in China. The results showed nitrogen inputs significantly contributed to wetland carbon dioxide (CO2) and nitrous oxide (N2O) emissions but had no significant effect on methane (CH4). We further analyze the relationship between greenhouse gases emissions and soil properties, climate factors under nitrogen inputs. Regression analyses introducing explanatory variables showed that high nitrogen inputs (12 g N m-2 yr-1-24 g N m-2 yr-1) contributed more significantly to wetland CO2 and N2O emissions. Compared to other wetland types, alpine peatlands have a greater impact on CO2 and N2O emissions following nitrogen input. In addition, high altitude (> 1500 m and ≤ 3500 m) could promote wetland CO2 and N2O emissions more significantly after nitrogen input, but ultra-high altitude (> 3500 m) reduced CO2 emissions. CO2 and N2O emissions were more significantly promoted when mean annual temperature (MAT) was positive, and CO2 emissions increased with increasing mean annual precipitation (MAP). Wetland CO2 emissions can be significantly promoted when soil is acidic, while N2O emissions can be significantly promoted when soil is alkaline. N2O emissions increased with increasing of soil total nitrogen (TN) and soil organic carbon (SOC) contents. These findings highlight the characteristics of wetland greenhouse gas emissions following nitrogen input, and improve our ability to predict greenhouse gas emissions and help meet carbon neutrality targets.

Soil nitrogen-related functional genes undergo abundance changes during vegetation degradation in a Qinghai-Tibet Plateau wet meadow.

Climate change and anthropogenic activities have significantly contributed to the degradation of wet meadows on the Qinghai-Tibet Plateau (QTP). Soil nitrogen (N) availability is a crucial determinant of the productivity of wet meadow vegetation. Furthermore, soil microbial nitrogen functional genes (NFGs) are critical in the transformation of soil N. Nevertheless, the dynamics of NFGs in response to vegetation degradation, as well as the underlying drivers, remain poorly understood. In this study, wet meadows at varying levels of vegetation degradation on the QTP, categorized as non-degraded (ND), slightly degraded (SD), moderately degraded (MD), and heavily degraded (HD), were examined. Soil samples from depths of 0 to 10 cm and 10 to 20 cm were collected during different growth cycles (June 2020, August 2020, and May 2021). The analysis focused on NFGs involved in organic nitrogen fixation (nifH), archaeal and bacterial ammonia oxidation (amoA-AOA and amoA-AOB, respectively), and nitrite reduction (nirK), utilizing real-time fluorescence quantitative PCR. Our findings indicate a significant decline in the abundance of NFGs with intensified vegetation degradation, exhibiting notable spatial and temporal fluctuations. Specifically, the relative NFGs followed the pattern: nirK > amoA-AOA > amoA-AOB > nifH. Redundancy analysis revealed that vegetation cover was the primary regulator of NFGs abundance, accounting for 56.1%-57% of the variation. Additionally, soil total nitrogen, pH, and total phosphorus content were responsible for 38.5%, 28.2%, and 7% of the variability in NFGs, respectively. The (amoA-AOA + amoA-AOB + nirK) ratios associated with effective N transformation indicated that the vegetation degradation process moderately increased the nitrification potential. IMPORTANCE: Our research investigates how the degradation of meadows affects the tiny organisms in soil that help plants use nitrogen, which is essential for their growth. In the Qinghai-Tibet Plateau, a region known for its unique ecosystems, we found that as meadows deteriorate-due to climate change and human activities-the number of these beneficial organisms significantly decreases. This decline could reduce soil fertility, impacting plant life and the overall health of the ecosystem. Understanding these changes helps us grasp how environmental pressures influence soil and plant health. Such knowledge is crucial for developing strategies to preserve these vulnerable ecosystems and ensure they continue to sustain biodiversity and provide resources for local communities.

Effect of plant species on wastewater treatment performance of a subsurface vertical-flow constructed wetland with step-feeding at low temperature.

To improve the treatment performance of constructed wetlands under low-temperature conditions, this study investigated the effects of plant species on wastewater treatment performance at low temperature and the associated microbiological characteristics in a subsurface vertical-flow constructed wetland (VFCW) with step-feeding. The results showed that the redox microenvironment in the VFCW filter with step-feeding could be restored and optimized by planting appropriate species that can tolerate low temperature, ensuring a high nitrification performance for the system. Correspondingly, the abundance and activity of three functional microbes (namely nitrifiers, denitrifiers, and anammox bacteria) increased to different degrees in the system, eventually ensuring ideal nitrogen removal by the VFCW. Compared with the VFCW planted with Phragmites australis and Acorus gramineus, the operation performance of the VFCW planted with Iris wilsonii could be recovered at low temperature, and its chemical oxygen demand, total phosphorus, total nitrogen, and ammonium nitrate removal rates could respectively reach 95.7%, 99.2%, 93.0%, and 94.4%, respectively. Moreover, nitrogen removal in the system relied on the nitrification/denitrification and partial denitrification - anaerobic ammonium oxidation processes. Nitrosomonas, Nitrospira, Thauera, and Candidatus Brocadia were the four dominant bacterial genera in the filter layer.