Freshwater Wetlands Research Articles

Water level and vegetation type control carbon fluxes in a newly-constructed soft-sediment wetland

Wetlands support unique biodiversity and play a key role in carbon cycles, but have dramatically declined in extent worldwide. Restoration is imperative yet often challenging to counteract loss of functions. Nature-based solutions such as the creation of novel ecosystems may be an alternative restoration approach. Targeted restoration strategies that account for the effects of vegetation on greenhouse gas (GHG) fluxes can accelerate the carbon sink function of such systems. We studied the relationships between vegetation, bare soil, and GHG dynamics on Marker Wadden in the Netherlands, a newly-created 700-ha freshwater wetland archipelago created for nature and recreation. We measured CO2 and CH4 fluxes, and soil microbial activity, in three-year-old soils on vegetated, with distinct species, and adjacent bare plots. Our results show that CH4 fluxes positively related to organic matter and interacted between organic matter and water table in bare soils, while CH4 fluxes positively related to plant cover in vegetated plots. Similarly, Reco in bare plots negatively related to water table, but only related positively to plant cover in vegetated plots, without differences between vegetation types. Soil microbial activity was higher in vegetated soils than bare ones, but was unaffected by substrate type. We conclude that GHG exchange of this newly-created wetland is controlled by water table and organic matter on bare soils, but the effect of vegetation is more important yet not species-specific. Our results highlight that the soil and its microbial community are still young and no functional differentiation has taken place yet and warrants longer-term monitoring.

Multi-sensor detection of spring breakup phenology of Canada's lakes

The ice phenology of freshwater lakes throughout the Northern Hemisphere has undergone important climate-induced shifts over the past century. In Canada's North, where freshwater lakes and wetlands cover 15 to 40% of the landscape, monitoring ice phenology is vital to understand its impacts on climate, socio-economic, ecological, and hydrological systems. The rapid and dynamic nature of ice phenology events has restricted monitoring efforts to the use of satellite sensors with frequent revisit times (e.g., MODIS, AVHRR), but their low resolution (e.g., > 500 m) limits observations to larger water bodies. However, the increased abundance of high-resolution open-access satellite imagery combined with the rise of cloud-computing technologies has provided opportunities to reduce the trade-off between temporal (i.e., revisit time) and spatial (i.e., pixel size) resolution allowing for lake ice monitoring over broad scales. In this study, we present the Open Pixel-based Earth eNgine Ice (OPEN-ICE) algorithm implemented in Google Earth Engine (GEE), which classifies imagery from multiple open-access optical sensors, then combines them to construct dense annual time series of ice-water observations and estimate pixel spring breakup dates at a 30-m resolution. Using Landsat 7 ETM+, Landsat 8 OLI, and Sentinel-2 MSI scenes over lakes spanning northern latitudes, we build reference datasets to train decision trees that discriminate between ice, water, and clouds. We combine ice-water classifications from each sensor into annual time series and remove misclassifications with a temporal filter applied using a pixel-wise logistic regression. We then detect the sequence of transition from ice to water in each pixel's time series to estimate the occurrence of breakup each year. We deploy the OPEN-ICE algorithm over all freshwater pixels of Canada for the period of 2013 to 2021. Spring ice phenology events estimated by OPEN-ICE show high accuracy when compared to whole-lake breakup dates measured by the Canadian Ice Service in 105 lakes across 9 years, with mean bias errors of −1.10 and − 0.69 days for breakup start and end, respectively. We apply the OPEN-ICE algorithm to 4000 lakes across Canada and evaluate differences in breakup dates across ecozones and lake sizes. Our new OPEN-ICE tool provides accurate estimates of annual spring breakup events applicable across all boreal and arctic regions to monitor the rapid changes taking place in these vulnerable ecosystems.

How does water diversion affect land use change and ecosystem service: A case study of Baiyangdian wetland, China

Baiyangdian wetland is the biggest plant-dominated shallow freshwater wetland in Huabei Plain, providing a wide range of ecosystem services. In the past few decades, the water scarcity and eco-environmental problems resulted from climate changes and human activities have become more and more serious. To relieve the pressure of water scarcity and ecological degradation, the government has implemented ecological water diversion projects (EWDPs) since 1992. In this study, land use and land cover change (LUCC) caused by EWDPs over three decades was analyzed to quantitatively assess the impact of EWDPs on ecosystem services. Coefficients of ecosystem service value (ESV) calculation were improved for regional ESV evaluation. The results showed that the area of construction, farmland and water increased by 6171, 2827, 1393 ha, respectively, and the total ESV increased by 8.04 × 108 CNY primarily due to the increase of regulating service with water area expansion. Redundancy analysis and socio-economic comprehensive analysis showed that EWDPs impacted water area and ESV with threshold and time effect. When the water diversion exceeded the threshold, the EWDPs affected the ESV through influencing LUCC; otherwise, the EWDPs affected the ESV through influencing net primary productivity or social-economic benefits. However, the impact of EWDPs on ESV gradually weakened as time passed, which could not keep sustainability. With the establishment of Xiong'an New Area in China and implementation of carbon neutrality policy, rational EWDPs will become crucial to achieve goals of ecological restoration.

A remote sensing‐based approach for spatiotemporal refined assessment of freshwater wetland ecological risk in coastal zones: A case in Jiangsu's coastal zone

AbstractRapid, long‐term, and robust wetland ecological risk assessment is critical for managing coastal zones. In view of the characteristics of frequent human activities and broken plots in the coastal zone, the traditional assessment method is not fine enough. Satellite earth observation provides an unparalleled source of data for rapidly monitoring and assessing coastal wetland ecological risks through time and across a large spatial range. With the support of multi‐source remote sensing data such as precipitation, temperature, night light, land cover products, etc., a wetland ecological risk assessment method is established in this paper, and the wetland ecological risk is evaluated year by year by a grid. The evaluation results indicate that the ecological risk level of coastal wetlands in Jiangsu Province has shown an upward trend since 2015, with a high ecological risk in the north and a low ecological risk in the south, and the source area mainly appears in the northwest. Meanwhile, the year‐by‐year grid assessment can not only accurately describe the spatial and temporal distribution of wetland ecological risks but also clarify the spatial and temporal characteristics of risk source areas. Additionally, the results obtained by year‐on‐year assessment of consecutive years and clustering and zoning according to the time‐series can better represent the risk status of the time period and exclude the impact of accidental factors on the evaluation results. Although optimization for different types of wetlands can improve the accuracy of assessment, more wetland risk assessment with a longer term and a larger scale, combined with carbon emissions, will provide a basis for global wetland management.

Responses of nitrogen cycling and related microorganisms to brackish wetlands formed by evapotranspiration

Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh (or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate (AOR), denitrifying rate (DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in China. Results showed that marsh ecosystems (ME) exhibited 31% higher AOR and 65% higher DR than non-marsh ecosystems (NE). For NE, freshwater non-marsh wetland exhibited 12% higher AOR than brackish non-marsh wetland. This was probably due to the inhibitory effects of high NH4+ and salinity levels on ammonia-oxidizing archaea in brackish non-marsh wetland. Conversely, DR in brackish non-marsh wetland was 23% higher than that in freshwater non-marsh wetland, with total organic carbon (TOC) significantly influencing this difference, suggesting that the higher DR in brackish non-marsh wetland was mainly due to its higher TOC level. For ME, due to the direct and indirect interference of salinity, brackish marsh wetland displayed 26% lower AOR and 19% lower DR than freshwater marsh wetland. Besides, brackish wetlands harbored distinct ammonia-oxidizing and denitrifying microbial communities compared to freshwater wetlands. The assembly of these communities was dominated by stochastic processes, while brackish wetlands exhibited more prominent deterministic processes than freshwater wetlands. Overall, high evapotranspiration altered activities and community characteristics of ammonia oxidizers and denitrifiers in inland brackish wetlands by enhancing salinity and nutrient levels, while emergent plants occurring in ME could mitigate the adverse effects of salt stress of inland brackish wetlands on nitrogen cycling.

Biological control of invasive floating fern leads to rapid recovery of ecological functions in coastal fresh water wetlands in Louisiana

Biological control of invasive floating fern leads to rapid recovery of ecological functions in coastal fresh water wetlands in Louisiana

Temperature and phosphorus: the main environmental factors affecting the seasonal variation of soil bacterial diversity in Nansi Lake Wetland.

The soil bacteria promote the circulation conversion of lake nutrients and play an important role in maintaining the balance of the lake ecosystem. Few studies have investigated the association of seasonal variation in bacteria and environmental factors in inland freshwater lake wetlands. Nansi Lake is a large shallow freshwater lake in northern China. It is an important hub of the eastern route of the South-to-North Water Diversion Project. In this study, bacterial 16S rRNA genes were used to analyze the variation of soil bacterial community diversity in Nansi Lake Wetland and its influencing factors in different seasons. It is showed that the phylum, family, and genus with the largest relative abundance in the soil of Nansi Lake Wetland are Proteobacteria, Nitrosomonadaceae, and MND1, respectively. There were significant seasonal differences in soil bacterial diversity in Nansi Lake Wetland, which was significantly higher in summer than in winter. Seasonal variation in environmental factors was significantly correlated with the variation in bacterial communities. Temperature and the content of available phosphorus may be the key factors influencing seasonal variation in bacterial diversity. The results of this study further enhance our understanding of the relationship between bacterial community diversity and environmental factors in the lake wetland ecosystem, which can provide scientific data for the conservation of Nansi Lake Wetland.

Morphological, ontogenetic, and molecular investigations of freshwater hypotrich ciliates from China revealed a new genus Heterodeviata gen. nov. (Protista: Ciliophora), and a novel limnetic population of Deviata multilineae

Abstract Hypotrichs are among the most complex and highly differentiated ciliate lineages, which are distributed in diverse habitats. Members of the family Deviatidae Foissner, 2016 are commonly found in freshwater or low-salinity habitats, as well as soils. During a study of freshwater wetland diversity in China, a novel deviatid ciliate Heterodeviata sinica gen. nov. et sp. nov. and a distinct population of Deviata multilineae Zhang et al., 2022 were investigated based on morphology, morphogenesis, and 18S rRNA gene sequences. The new genus Heterodeviata gen. nov. can be characterized by having two or more left and right marginal rows each, one frontoventral cirral row, the presence of caudal cirri, and two dorsal kineties, one of them being a dorsomarginal kinety. Phylogenetic analyses reveal that Heterodeviata is nested in a well-supported clade with Deviata Eigner, 1995, Perisincirra Jankowski, 1978 and Pseudosincirra Gao et al., 2021, which suggests that the family Deviatidae is monophyletic. The close relationship among the Deviatidae genera were supported after extensive morphological and morphogenetic investigations, as well as molecular phylogeny presented here.

“Safe” Sequestration of Additional Phosphorus in Freshwater Wetland and Salt Marsh at Coastal Zone in the Yellow River Delta

“Safe” Sequestration of Additional Phosphorus in Freshwater Wetland and Salt Marsh at Coastal Zone in the Yellow River Delta

Investigation of the concentration, origin and health effects of PAHs in the Anzali wetland: The most important coastal freshwater wetland of Iran

This study investigated the concentration of PAHs in 19 water samples, 34 sediment samples and 22 fish samples of Anzali Wetland, located in north of Iran. The average concentration of ∑PAHs in the wetland sediment was 89.19 μg/kg (8.28–806.64) and 78.31 ng/L (5.14–253.37) in the wetland water. Also, the average concentration of ∑PAHS in the muscle of the investigated fish in the wetland was 23 μg/kg (56.1 to 7.6). The source apportionment of PAHs in water and sediment considering isomeric ratios and statistical methods reveals the predominance of petrogenic origin of the compounds in water and pyrogenic origin in sediment. Overall, the level of contamination in fish is relatively low to moderate, considering ∑PAHs. The findings present clear evidence of low to moderate level of contamination in the wetland, the PAHs contamination however could cross their ecological thresholds in future unless control measures are taken to protect the wetland.

Wetland management practices and secretive marsh bird habitat in the Mississippi Flyway: a review

AbstractManagement regimes on publicly owned freshwater wetlands in the Mississippi Flyway of North America (i.e., Flyway) have historically emphasized waterfowl, but there is limited information on how waterfowl‐focused wetland management affects other wetland‐dependent wildlife. Secretive marsh birds (SMBs) depend on wetlands with emergent vegetation throughout their migratory life cycle and often encounter vegetation and water conditions resulting from waterfowl‐focused management regimes. Thus, there is a need for better understanding of how SMBs are affected by wetland management and the extent to which waterfowl‐focused management regimes provide habitat for SMBs. In this review, we identify the vegetation and water conditions resulting from typical management objectives on freshwater emergent wetlands in the Flyway, review and qualitatively synthesize results from studies that directly evaluate how wetland management practices affect SMBs or their habitat, and assess how the vegetation and water conditions being produced for target species (mainly waterfowl) align with SMB habitat requirements. We searched online databases and used Google Scholar to locate peer‐reviewed literature, technical reports, and graduate theses that pertained to responses of SMBs or their habitat to water‐level manipulation, herbicide application, prescribed fire, disking, mowing, and planting crops. There are several management strategies that complement SMBs and waterfowl, such as reducing cover of woody species and providing flooded emergent vegetation. We also highlight management strategies that may not currently align with SMB life‐cycle needs and suggest adjustments that might promote habitat for SMBs while still achieving waterfowl population objectives. For example, adjusting the dates and duration of spring water‐level drawdowns on a portion of wetlands within a larger complex can provide for spring migrating waterfowl and ensure habitat for migrating and nesting SMBs. Ideally, future studies would address how modifications to management practices affect SMBs and monitor potential effects on waterfowl, resulting in a more holistic approach to wetland management.

Hydrological connectivity shapes multiple diversity facets of snail (Mollusca: Gastropoda) assemblages in freshwater floodplain wetlands

Hydrological connectivity is crucial for supporting aquatic biodiversity and serving ecosystem function in river floodplain wetlands. Although the effects of longitudinal connectivity in the composition of snail (Mollusca: Gastropoda) assemblages is well understood, the effects of lateral connectivity are less evaluated. Here, we evaluated the effects of lateral and longitudinal connectivity on multiple facets of alpha and beta diversity (i.e., taxonomic, functional, and phylogenetic) of freshwater snails in 38 floodplain wetlands in the Da Xing'an Mountains of Northeast China. A total of 9,784 snails subjected to 5 orders, 14 families, 24 genera, and 42 species were collected. Overall, the snail alpha diversity was higher in the nearly isolated wetlands and downstream areas. Multivariate analyses revealed that the taxonomic, functional, and phylogenetic structures of snail assemblages in floodplain wetlands differed significantly across the lateral and longitudinal gradients. Waterscape and climate variables appeared to equivalently explain a large proportion of variations in the taxonomic, functional, and phylogenetic structures of snail assemblages. Lateral connectivity and river order were paramount variables that explain the greatest variation in taxonomic, functional, and phylogenetic structures of the snail assemblages. Our study suggests that hydrological connectivity is a key factor controlling the multiple facets of snail diversity in floodplains. Attention should be paid to the effects of changing climate and waterscape on the multi-faceted diversity of snail assemblages. Due to the extant patterns in assemblage structures, floodplain restoration and management should consider the full spectrum of longitudinal and laterally connectedness to maximize aquatic biodiversity.

Incorporating biotic phosphorus-acquisition strategies into soil phosphorus transformation under long-term salinization in a tidal wetland

Tidal wetland plants can maintain high primary productivity under salinization, even with low phosphorus (P) availability. However, little is known about how they adapt to salinization-induced ecosystem P limitation over time. We established mesocosms using tidal freshwater wetland soils and the salt-tolerant plant Cyperus malaccensis and subjected them to short-term (6 months) and long-term (3.5 years) salinization. Overall, short-term salinization did not change plant or microbial biomass nitrogen/P ratios, whereas long-term salinization increased both, indicating that short-term salinization did not alter ecosystem P limitation, but long-term salinization exacerbated it. Concurrently, short-term salinization reduced the moderately labile inorganic P (Pi) pool, whereas long-term salinization also reduced the hydrolyzable organic P (Po) and primary mineral P pools. During both short- and long-term salinization, moderately labile Pi mobilization exhibited a negative correlation with Fe sulfide concentration and a positive correlation with Fe(III) concentrations. These results suggested that both short- and long-term salinization obtained P through abiotic P-acquisition strategies. Mobilization of the primary mineral P pool and hydrolyzable Po pools was negatively linked to root arbuscular mycorrhizal fungi (AMF) biomass and soil alkaline phosphomonoesterase (ALP) activity, respectively. This indicated that long-term salinization acquired P via biotic P-acquisition strategies. Specifically, soil microorganisms increased fungi predominance and thereby increased ALP activity to convert hydrolyzable Po, while tidal wetland plants enhanced root AMF associations to release carboxylate to transform primary mineral P. Overall, our results highlight that abiotic P-acquisition strategies could offset the ecosystem P limitation during short-term salinization, whereas biotic P-acquisition strategies play a more important role in soil P transformation under long-term salinization. Through biotic P-acquisition, tidal wetland ecosystems can maintain high plant primary productivity through biotic P-acquisition even under P-limited conditions, exhibiting increased resilience to sea-level rise.

Aquatic phosphorus behaviour within a UK Ramsar wetland: Impacts of seasonality and hydrology on algal growth and implications for management

Fundamental to all life, phosphorus is an essential nutrient and, contrastingly, a significant threat to surface water biodiversity globally as one of the most common causes of eutrophication in surface waters worldwide. Freshwater wetland ditches affected by these conditions undergo a conversion from primarily submerged aquatic vegetation to algae or duckweed dominance, leading to anoxic conditions. However, macrophyte biomass harvesting in eutrophic water systems is a promising means of remediation and nutrient recycling. This study seasonally assesses spatial distribution and chemical fractionation of surface water phosphorus, as well as surface biomass abundance and total phosphorus content in the ditch systems at West Sedgemoor (Somerset, UK), a designated site of special scientific interest. Elevated phosphorus concentrations in the surface water were observed across the site, with all sites exceeding e hi the Common Standards Monitoring environmental quality standard value of 0.1 mg L−1 during summer and autumn Sites lacking hydrological flow connectivity with contaminated freshwater inputs, typically had lower surface water phosphorus concentrations than the rest of the moor, with localised hotspots associated with likely cattle related agricultural activity. Summer and autumn were determined as the dominant duckweed growth seasons, in which an estimated 39 kg of phosphorus could be removed via duckweed biomass harvesting, per harvest period.

Methane Emissions Are Highly Variable across Wetland Habitats in Natural and Restored Tidal Freshwater Wetlands

Methane Emissions Are Highly Variable across Wetland Habitats in Natural and Restored Tidal Freshwater Wetlands

Effects of temperature and heat waves on embryonic development of annual fishes from Neotropical wetlands: Implications for climate change scenarios

AbstractClimate change projections predict warmer temperatures and increased frequency of heat waves in many regions across the globe. These scenarios are expected to strongly impact temperature‐dependent life‐history traits of aquatic species, such as the embryonic stage of annual fishes inhabiting temporary freshwater wetlands. Here, we assessed the effects of different incubation temperatures (18, 24, 27 and 30°C) and exposure to heat waves (18–30°C for 6 h) on aspects of the embryonic development: mortality and trajectory (direct development or diapause entry) of two Neotropical species of annual fishes from high‐ (Austrolebias nubium) and low‐altitude (A. cyaneus) areas. Temperatures of 30°C resulted in 100% embryo mortality in both species, and development trajectory differed between species across temperatures. Embryo mortality in the high‐altitude species was higher at 27°C, while a higher number of embryos of the low‐altitude species entered diapause II at 18°C. Embryo mortality and development trajectory after exposure to heat waves were similar between species. In terms of implications for climate change scenarios, temperatures above 27°C seem critical for the embryo survival of both species studied, although they seem capable to endure short‐term events of heat waves. In summary, our results indicate that the persistence of populations of high‐altitude annual fish species may be subject to higher threat under warming scenarios, since embryos from this species were more sensitive to increasing temperatures than the low‐altitude species.

Participatory Rural Appraisal for Assessing Freshwater Wetland Status and Fishery Potential in West Midnapore, West Bengal, India

Participatory Rural Appraisal for Assessing Freshwater Wetland Status and Fishery Potential in West Midnapore, West Bengal, India

HERPETOFAUNA OF THE CHASCHOC LAGOON WETLANDS, TABASCO, MEXICO

This study apports new information on the diversity of amphibians and reptiles in a freshwater wetland of Tabasco. From January to December 2014, monthly samplings were conducted in the Chaschoc lagoon wetlands to establish a checklist of amphibians and reptiles for this site and to detect potential threats to their conservation. Diurnal and nocturnal surveys were conducted in terrestrial habitats, while surveys were conducted in water bodies for turtles and crocodiles. Fifty-five species were detected (12 amphibians, and 43 reptiles), representing 32.4% of the species recorded for Tabasco. Species accumulation models resulted in percentages of inventory completeness above 92 %. Most of the species do not appear in IUCN Red List of threatened species, appendices of CITES, or the list of threatened species of the Official Mexican Norm NOM-59-SEMARNAT-2010. Main threats detected for the herpetofauna were cattle ranching, illegal hunting and collecting, destruction, fragmentation and pollution of the habitat, and intentional fires. We also detected three non-native invasive species of reptiles.

Investigating the potential for a blue carbon economy on Australia’s northern coastline

The term ‘Blue Carbon’ (BC) recognises the ability of mangroves, saltmarshes, and seagrasses to capture and store carbon in their soils and biomass. Given their anoxic sediment, BC ecosystems can sequester up to as much as four times more carbon per hectare, and store it 30–50 times faster, than terrestrial forests. Australia has some of the world’s largest BC storage capacity, with 5–11% of global BC soil stocks and 2–7% of annual BC sequestration, based on available global estimate. Evidence indicates that mangrove and saltmarsh degradation from cyclone damage, feral damage and disease, is occurring throughout the Northern Territory (NT). This is a growing issue with feral animal populations degrading Indigenous lands and areas of conservation significance. This cumulative pressure on BC habitat means that northern Australia is uniquely positioned to expand BC methods to also account for protection and restoration of degraded coastal habitats including freshwater wetlands that have been damaged by non-native feral animals. Researchers from Charles Darwin University (CDU), University of Queensland (UQ), and the Northern Australian Indigenous Land and Sea Management Alliance Ltd (NAILSMA) recently worked to explore the opportunity and potential for economically viable BC methods in the NT. The study had a particular focus on Aboriginal Land gazetted under the Aboriginal Land Rights (NT) Act (1976) (Cth). We present the research outcomes and identify the pathway to focused research on BC stores and tailored methods for generating Australian Carbon Credit Units (ACCUs) and potentially biodiversity credits, in the NT.

Spectral characteristics analysis of typical ground objects in Poyang Lake wetland based on “Zhuhai-1” hyperspectral data

Hyperspectral image data provides new ideas and methods for the fine classification of wetland. Research on wetland spectral characteristics lays the foundation for wetland classification and improves classification accuracy. Based on “Zhuhai-1” hyperspectral image data, combined with the Pure Pixel Index (PPI), this paper extracted the average spectral curves of 11 typical ground objects in Poyang Lake wetland. Two mathematical transformation methods, namely, the continuum removal and the first derivative, were used to analyze the spectral characteristics of the ground objects before and after transformation, in combination with spectral characteristic parameters. The method of combining the mean distance of ground objects with the range of data error was used to select characteristic wavelengths before and after spectral transformation. Finally, the Mahalanobis distance method was used to verify the recognition effect. The results demonstrate that: (1) Spectral transformation can effectively amplify the differences between ground objects. The continuum removal led to an increase in the characteristic bands of four types of vegetation and the emergence of characteristic bands of four types of other ground objects. The first derivative method extended the characteristic bands of four vegetation from red-edge to near-infrared. (2) The method of combining the mean distance and the data error range can effectively screened out the spectral characteristic bands of typical ground objects in Poyang Lake wetland, resulting in hyperspectral dimensionality reduction. (3) The Mahalanobis distance method validates the recognition effect of the characteristic bands. In the screened characteristic bands, the Mahalanobis distance between different ground objects is larger than that between the same ground object, except between shoaly land and road. This study offers valuable insights into spectral recognition and classification of freshwater lake wetlands, and also demonstrates the potential of “Zhuhai-1” hyperspectral image data in wetland research.