Altered Wetlands Research Articles

Secretive marsh bird occupancy across a spectrum of hydroelectric reservoir management in western montane Canada

AbstractDam construction projects have created opportunities for water security, targeted flood protection, and energy production but at the cost of increasing anthropogenic pressure on affected aquatic ecosystems. Wetland ecosystems are often among the most vulnerable, as underlying hydrological regimes influence overall wetland structure and function. Marsh bird species are wetland and riparian habitat specialists, many of which are experiencing population declines across North America. We examined how the alteration of hydrological regimes for generating hydroelectric power affected the occurrence of secretive marsh bird species in the western montane region of British Columbia, Canada. We established survey stations in wetlands across 2 regions, the West Kootenay and the Columbia Wetlands, sampling across a spectrum of hydrological regimes and other potentially relevant factors. At each station, we assessed wetland occupancy during the breeding season using broadcast‐callback surveys focused on 5 secretive marsh bird species: American bittern (Botaurus lentiginosus), American coot (Fulica americana), pied‐billed grebe (Podilymbus podiceps), sora (Porzana carolina), and Virginia rail (Rallus limicola). Additionally, we measured vegetation structure and the proximity and size of nearby water bodies for each survey station. We then used occupancy models to assess important correlates behind wetland occupancy for these marsh bird species, considering water management operations, regional differences, and local‐ and landscape‐level wetland characteristics. Secretive marsh bird species were more likely to occupy wetlands in areas with less frequently altered hydrological regimes. Occupancy models highlighted local‐ and landscape‐level characteristics as important correlates for wetland occupancy by marsh birds. Wetlands with frequently altered hydrological regimes had more open water cover and less tall vegetation present, conditions that were negatively associated with occupancy. Altered wetlands in this study were farther from the next nearest wetland, which was also negatively associated with occupancy. We suggest reservoir management is altering vegetation communities within these wetlands, indirectly promoting lower occupancy of secretive marsh bird species.

Wetland Vegetation Response to Groundwater Pumping and Hydrologic Recovery

An investigation of wetland vegetation response to groundwater alteration was conducted at the J.B. Starkey Wilderness Park, a large municipal wellfield in the area of west Florida, USA. Decades of historic groundwater withdrawal had created a gradient of impacted wetlands on the wellfield, after which time the groundwater pumping rates were reduced. Nineteen cypress dome wetlands were grouped, based on their hydrologic histories, as either most-altered (least inundation), marginally-altered (intermediate inundation), or least-altered (near-normal inundation). Annual species–level monitoring data were used to evaluate understory plant community response to the hydrologic recovery that resulted from reduced groundwater pumping. Species richness, cover, prevalence index (PI), and species importance percentages were assessed during pre- (2005–2007) and post- (2012–2014) hydrologic recovery periods. The vegetation in marginally- and most-altered wetlands responded to hydrologic recovery with increased species richness and lower PI values (i.e., greater hydrophytic character). However, species importance percentages indicated greater variation in the recovery of most-altered wetlands, where species composition often remained different from least-altered wetlands. Although reductions in groundwater pumping caused sufficient passive hydrologic recovery to elicit a vegetation response, further reductions and/or more time may be needed before the vegetation of some altered wetlands can become comparable to that of least-impacted wetlands.

Temporal Patterns of Wetland-Associated Bird Assemblages in Altered Wetlands in Turkey

A loss of wetlands, one of the highly sensitive ecosystems, necessitates the monitoring and assessment of wildlife population trends for the continuity and sustainable management of species. The goal of our study was to evaluate temporal changes in wetland-associated bird composition by conducting monthly counts during December 2006 - November 2007 and March 2015 - February 2016 in Efteni Lake, Duzce, Turkey. This lake has been exposed to structural change including shoreline length, area and depth for the last 50 years. Wetland-associated bird richness decreased, and abundance increased during the decade, but this change was not significant except for two species with an increased population, ferruginous duck Aythya nyroca and great crested grebe Podiceps cristatus. Cluster analyses resulted in two groups: the breeding season from April to September, and the non-breeding season from October to March. The most numerous species were observed mostly during the non-breeding season. Some guilds, including diving carnivores, omnivores, shoreline omnivores and herbivores species were more prevalent during the non-breeding season. The insectivores had higher population densities during the breeding season. Thus, wetland-associated bird abundance during the non-breeding season was higher than during the breeding season, although species richness was the opposite. The planned restoration of habitats of Efteni Lake should have a positive impact on birds by creating more space available to them. Our result should help to better understand the impact of habitat changes on waterbird assemblages. Long-term monitoring of Efteni Lake will be useful for the wetland-associated avian community, and for other animal and plant communities.

Sustainability of constructed wetlands using biochar as effective absorbent for treating wastewaters

Coconut shell as biochar was acquired by warm disintegration of natural material under limited supply of oxygen. It offers basic and financially savvy techniques to treat wastewater and diminishing carbon impression. Combination of both (constructed wetland and biochar) advancements was established to expand the efficiency in the treatment of domestic and tannery wastewater. Reduction in parameters such as pH, turbidity, and other physico-chemical parameters from domestic and tannery wastewater utilizing biochar from coconut shell was researched by blending the biochar with the wetland soil. The biochar altered wetlands demonstrated noteworthy reduction efficiencies of 99.9% and 85% in turbidity and TDS when contrasted with the normal wetlands which showed an effectiveness of 98% and 77.7% in reducing turbidity and TDS, for domestic wastewater. For tannery wastewater, the biochar mixed wetlands demonstrated a reduction efficiency of 99% and 83% in turbidity and TDS, separately when contrasted with the ordinary wetlands which displayed a reduction efficiency of 87% and 74% in reducing turbidity and TDS. The normal wetlands showed better productivity of 93% in nitrogen reduction when contrasted with biochar wetlands with a reduction efficiency of 77%. Concentration of Cr has been diminished marginally more in biochar wetlands.

Assessing the Changes of Ecosystem Services in the Nansi Lake Wetland, China

Wetlands provide many essential ecosystem services for human well-being. The ecological assessment of wetland ecosystem services is problematic and thus is an important focus in the field of ecological research. In this study, an ecological assessment system containing the ecosystem product value, ecosystem regulation service value, and ecosystem cultural service value was established to calculate the gross ecosystem product in the Nansi Lake Wetland, China. Based on remote sensing images, field studies, and literature reviews, the gross ecosystem product was estimated for the years 1985, 1992, 2005, 2011, and 2017. The results showed that the gross ecosystem product of the Nansi Lake Wetland increased from 40.91 × 108 USD in 1985 to 46.28 × 108 USD in 2017. The gross ecosystem product of the altered wetlands increased by about 8.5 times with a rising linear relationship, while natural wetlands presented a nonlinear relationship. Furthermore, except for the changes in climatic condition, anthropogenic interference factors such as coal mining activities, farming practices, and government policies have promoted significant services in the Nansi Lake Wetland over the past 30 years. This study could provide important insight into the ecological assessment of wetland ecosystems and thus inform policy for the protection and better use of wetland resources.

Soil Conditions Following Hydrologic Restoration in Cypress Dome Wetlands

Soil characteristics and decomposition rates were investigated in 12 geographically isolated wetlands (cypress domes) across a gradient of hydrologic alteration (altered, marginally altered and least altered sites) seven years after passive recovery from historic groundwater withdrawals. Above- and belowground decomposition rates were determined in transition (seasonally flooded) and outer deep (semi-permanently) hydrologic zones. Flood duration, frequency, redox conditions, pH, and soil organic matter were measured to potentially explain patterns across the alteration gradient. Despite the reduction in groundwater withdrawals, altered sites exhibited fewer days of inundation in transition and outer deep zones compared to marginally altered and least altered wetlands. Over a 56 week period, altered wetlands displayed greater decomposition in the aboveground outer deep zone (73.3 ± 4.0% mass remaining) and in the belowground transition zone (62.0 ± 4.5% mass remaining) compared to marginally and least altered sites. Analyses indicated that marginally altered wetlands were more comparable to least altered wetlands however differences in altered wetland soils (including decomposition) persist. Although wetland hydrology has been partially restored, additional time and/or further site augmentation may be needed for altered sites to be functionally equivalent to least altered wetlands and in some cases (e.g., excessive subsidence) the degree of past alteration may limit restoration potential.

Impacts of human-induced environmental change in wetlands on aquatic animals.

Many wetlands harbour highly diverse biological communities and provide extensive ecosystem services; however, these important ecological features are being altered, degraded and destroyed around the world. Despite a wealth of research on how animals respond to anthropogenic changes to natural wetlands and how they use created wetlands, we lack a broad synthesis of these data. While some altered wetlands may provide vital habitat, others could pose a considerable risk to wildlife. This risk will be heightened if such wetlands are ecological traps-preferred habitats that confer lower fitness than another available habitat. Wetlands functioning as ecological traps could decrease both local and regional population persistence, and ultimately lead to extinctions. Most studies have examined how animals respond to changes in environmental conditions by measuring responses at the community and population levels, but studying ecological traps requires information on fitness and habitat preferences. Our current lack of knowledge of individual-level responses may therefore limit our capacity to manage wetland ecosystems effectively since ecological traps require different management practices to mitigate potential consequences. We conducted a global meta-analysis to characterise how animals respond to four key drivers of wetland alteration: agriculture, mining, restoration and urbanisation. Our overarching goal was to evaluate the ecological impacts of human alterations to wetland ecosystems, as well as identify current knowledge gaps that limit both the current understanding of these responses and effective wetland management. We extracted 1799 taxon-specific response ratios from 271 studies across 29 countries. Community- (e.g. richness) and population-level (e.g. density) measures within altered wetlands were largely comparable to those within reference wetlands. By contrast, individual fitness measures (e.g. survival) were often lower, highlighting the potential limitations of using only community- and population-level measures to assess habitat quality. Only four studies provided habitat-preference data, preventing investigation of the potential for altered wetlands to function as ecological traps. This is concerning because attempts to identify ecological traps may detect previously unidentified conservation risks. Although there was considerable variability amongst taxa, amphibians were typically the most sensitive taxon, and thus, may be a valuable bio-indicator of wetland quality. Despite suffering reduced survival and reproduction, measures such as time to and mass at metamorphosis were similar between altered and reference wetlands, suggesting that quantifying metamorphosis-related measures in isolation may not provide accurate information on habitat quality. Our review provides the most detailed evaluation to date of the ecological impacts of human alterations to wetland ecosystems. We emphasise that the role of wetlands in human-altered ecosystems can be complex, as they may represent important habitat but also pose potential risks to animals. Reduced availability of natural wetlands is increasing the importance of altered wetlands for aquatic animals. Consequently, we need to define what represents habitat quality from the perspective of animals, and gain a greater understanding of the underlying mechanisms of habitat selection and how these factors could be manipulated. Furthermore, strategies to enhance the quality of these wetlands should be implemented to maximise their conservation potential.

Levantamento populacional do cervo-do-pantanal Blastocerus dichotomus (Mammalia, Cervidae) no Parque Nacional de Ilha Grande e entorno: implicações para a conservação

Nós conduzimos um levantamento populacional aéreo do cervo-do-pantanal, Blastocerus dichotomus (Illiger, 1815), no Parque Nacional de Ilha Grande e seu entorno, entre os estados do Paraná e Mato Grosso do Sul, Brasil, na estação seca. Utilizamos a técnica da contagem dupla, e a população foi estimada em 1.079 ± 207 cervos em uma área amostral de 1.081 km², corresponde a uma densidade de 0,998 ± 0,192 ind/km². A população mostrou-se mais concentrada no interior do parque, ocupando também várzeas alteradas fora dos limites do parque. Estes resultados devem subsidiar medidas de manejo e conservação da população no parque nacional e seu entorno, devido à enorme pressão antrópica sobre a população de cervos na região.

Evaluation of groundwater and phosphorus transport in fractured altered wetland soils

Nutrient loss from altered wetlands to waterways may influence the water quality of downstream water resources. To test potential nutrient transport from a highly fractured agricultural field of altered wetland to waterways, we computed water and solute budgets in a large field (320 ha) experiment. The water level was raised in a drainage canal for 28 days (raising stage) to generate water flow to the field and then lowered (drainage stage) to generate back flow to the canal. Differential sampling stations (DISS) equipped with an Eh-pH measuring system were installed to monitor and sample crack and matrix water separately. Water flowing in cracks exhibited Eh > 250 mV and EC < 1.5 dS m ―1 while in the matrix, the Eh was <100 mV and EC exceeded 3.0 dS m ―1 . High similarity was found between crack water measured in the DISS and water that drained directly into the drainage canal. We proposed a conceptual model for water and solute transport by a dual-domain system. Most of the water flow occurs in the cracks and most of the solute reaches the cracks by advection and diffusive flow mechanisms in the soil matrix. The conceptual model is based on the assumption that the crack and matrix domains are in chemical disequilibrium because of low transport rate from the matrix to the cracks relative to water flow rate in the cracks. Using this conceptual model, we calculated that during the drainage stage, only 0.64 kg P, compared with 3700 kg of the non-sorptive sulfate ion, were transported from the field to the canal. The oxidized conditions in the crack walls lead to Fe-hydroxide precipitation. These fresh precipitate amorphous iron hydroxides serve as an adsorption sink to P and other potential adsorbates.

Using Hydrologic Equivalent Wetland Concept Within SWAT to Estimate Streamflow in Watersheds with Numerous Wetlands

Using models such as the Soil and Water Assessment Tool (SWAT) to quantify the conveyance, storage, and retention functions of wetlands is a cost-effective means of generating the scientific information required for watershed management and protection/restoration. However, it has been a challenge to appropriately represent wetlands in models, and few SWAT applications reported in the literature have considered wetlands. The objectives of this study were to (1) demonstrate how to incorporate wetlands into a SWAT model using a hydrologic equivalent wetland (HEW) concept and (2) use the SWAT model to simulate the streamflows in the 4506 km 2 upper portion of the Otter Tail River watershed in northwestern Minnesota. The HEWs were defined in terms of six calibrated parameters: the fraction of the subbasin area that drains into wetlands (WET_FR), the volume of water stored in the wetlands when filled to their normal water level (WET_NVOL), the volume of water stored in the wetlands when filled to their maximum water level (WET_MXVOL), the longest tributary channel length in the subbasin (CH_L1), Manning's n value for the tributary channels (CH_N1), and Manning's n value for the main channel (CH_N2). The model performance was judged in terms of three statistics: the Nash-Sutcliffe coefficient (Ej 2 ), the coefficient of determination (R 2 ), and the performance virtue (PVk). For the study area, the HEWs were determined to have a value for WET_FR ranging from 50% to 96%, i.e., draining more than 50% of the subbasins, depending on the spatial distribution and types of the wetlands in each subbasin. A with a minimal alteration tended not to contribute water to the streams until it reached its maximum capacity, as indicated by identical calibrated values for WET_NVOL and WET_MXVOL for all the subbasins except for the three that included altered wetlands. The results indicated a strong linear relationship between WET_NVOL and the corresponding surface area (R2 = 0.98) and an overall average depth of 0.85 m for the HEWs. The parameters WET_NVOL and WET_MXVOL may primarily represent the storage function of the wetlands, whereas the conveyance and retention functions would be reflected by the latter five parameters. In addition, the SWAT model incorporating the HEW assumption had an acceptable or satisfactory performance in simulating the streamflows for an evaluation period from 1 December 1969 to 31 May 1975 at daily, monthly, seasonal, and annual time steps (Ej 2 > 0.36, PVk > 0.75), although its performance varied from one evaluation station to another and might be weak for spring and fall in some evaluation years. Nevertheless, additional model runs with the no wetland and synthetic wetland assumptions, which are two approaches typically used to deal with wetlands for modeling purposes, indicated that the HEW concept is superior in incorporating wetlands into SWAT for the study area.

Oxygen depletion and phosphorus release following flooding of a cultivated wetland area in Denmark

Geografisk Tidsskrift, Danish Journal of Geography 108(2):17–25, 2008 The rewetting of altered wetlands is becoming increasingly widespread. When flooding cultivated soils, the oxygen (O2) availability is reduced, subsequently, ferric hydroxides can dissolve and associated inorganic phosphorus (P) will be mobilized. This study shows the temporal and spatial dynamics of O2 depletion following flooding using planar optodes and the subsequent release of Fe and P in two depth intervals in an experimental column set-up. The column was kept flooded for 48 days and thereafter partly drained and flooded again. Results document that large amounts of P (0.2 t P ha-1) have accumulated in the present plough-layer (Ap) during the last 22 years, which represent roughly 15% of the present inorganic P stock in the Ap. As a result of flooding, fully anoxic conditions were observed within 3 days (within 10 h in Ap) and concentrations of dissolved Fe and P in the soil solution increased simultaneously after 7 days of flooding. Thus, P reaction kinetics was markedly delayed as compared to O2 availability. P concentrations in soil water afterflooding (up to 0.15 mg L−1) accounted for only 0.034% of the inorganic P stock in the Ap which is a significantly smaller fraction of the potential P-release as compared to previous investigations. This is considered a result of only a minor fraction of the total inorganic P being directly associated with ferric hydroxides and thereby sensitive to short-term anoxic conditions as well as differences in the methodology used in this study (soil/water ratio). Finally, reactions releasing Fe and P were noted to be partly reversible upon draining.

The Geochemistry of Phosphorus in Peat Soils of a Semiarid Altered Wetland

An understanding of P transformations in altered wetlands has mainly developed from temperate and humid regions with neutral to acidic soils. Little is known regarding downstream water quality impact of P transformations in semiarid wetlands that undergone repeated cycles of drying and rewetting. The P geochemistry was studied using the Hedley fractionation scheme in the altered peat soils of the Hula Valley, Israel. The peat soils were sampled according to the peat depth and redox potential characteristics. The mean total P concentration (Pt) in the surface peat horizons (1190 ± 300 mg kg−1) was significantly higher than in the anaerobic (EH &lt; −220 mV) peat layers (650 ± 260 mg kg−1). The concentrations of P in all fractions except the most labile P were significantly higher in the aerobic (EH = 400 mV) peat layers. The predominant extractable fractions in the surface peat horizons were Ca‐P extracted by 1 M HCl (21–60% of Pt), Iron‐P extracted by 0.5 M NaOH (11–41% of Pt), and residual P extracted by H2SO4 (20–40% of Pt). The source of the Ca in the Ca‐P fraction was mainly from gypsum dissolution following the rewetting cycles. The results clearly showed that the drainage of these wetlands facilitated rapid organic matter (OM) oxidation, release of organically bound metals and P followed by sesquioxides and gypsum precipitation. These geochemical transformations enhanced the Pt concentration per mass of altered peat soil and changed the P distribution among the different pools. Most of the P is currently associated with Fe oxides and hydroxides and/or coprecipitated with Ca.

Effects of wetland excavation on avian communities in eastern Washington

Despite having an arid climate, the Columbia River Basin of eastern Washington is one of the most important areas for breeding, migrating, and wintering wetland birds in the Pacific Northwest. Extensive farmland irrigation near the O’Sullivan Reservoir and other areas has raised water tables, resulting in closed canopies of emergent vegetation in what are now permanent, shallow wetlands. During 1994–95, we found that avian communities on vegetation-filled wetlands excavated to create open water had greater mean densities of dabbling and diving ducks (Anatidae), shorebirds, American coots (Fulica americana), and terns (Sterna spp.) than untreated control wetlands. Densities of yellow-headed blackbirds (Xanthocephalus xanthocephalus) were greater on excavated wetlands, while the densities of red-winged blackbirds (Agelaius phoeniceus), Sora (Porzana carolina), and Virginia rails (Rallus limicola) were greater on unaltered sites. Densities of marsh wrens (Cistothorus palustris) and other passerines were similar among excavated and control wetlands. Zooplankton biomass was greater on altered wetlands and generally greater in older excavations. We suggest that managers may design constructed wetland basins to improve population management of diverse wetland bird species by creating an appropriate mix of wetland habitats at the landscape level.

Ecological functions and human values in wetlands: A framework for assessing forestry impacts

The term “value” usually connotes something of use or desirable toHomo sapiens. Values ascribed to many wetlands include providing habitats for fishing, hunting, waterfowl, timber harvesting, wastewater assimilation, and flood control, to name a few. These perceived values arise directly from the ecological functions found within the wetlands. Ecosystem functions include hydrologic transfers and storage of water, biogeochemical transformations, primary productivity, decomposition, and community/habitat. An analysis of the relationship among wetland functions and values, showed that over-utilization or intensive removal of wetland values (e.g., timber harvesting with drainage), can often result in a loss of specific wetland functions. An assessment procedure comparing changes in wetland function from both a disturbed and reference wetland was developed. This approach scales the wetland functions in a reference system to 100% and then compares the altered wetlands’ functional response. Methods to analyze wetland functions in the field are outlined along with examples of the effects of forestry activities on wetland response.