Wetland Health Research Articles

Use of single versus multiple biotic communities as indicators of biological integrity in northern prairie wetlands

As much as 70% of prairie wetlands in Canada have been lost. Although further degradation of natural wetlands is considered to be somewhat offset by wetland construction and restoration, Canada lacks bioassessment tools that can track ecosystem health in prairie wetlands. Indices of biological integrity (IBIs) use one or more biotic communities to compare the biological condition of a particular site to conditions found in least-impacted reference sites. Using the IBI approach, we evaluated the potential of 5 biotic communities to assess wetland health in northern prairie wetlands in Canada. Vegetation in the wet meadow, emergent and open-water zones as well as wetland-dependent songbirds and waterbirds were sampled at 81 semi-permanent/permanent natural and compensation wetlands spanning an environmental stress gradient. Metrics with strong linear relationships to the stress gradient (R2>0.2) were combined into an IBI for each biotic community and were subsequently validated at a suite of test sites. After validation, the entire data set was combined and each IBI was evaluated based on its linear relationship to environmental stress. Wet meadow zone vegetation was a strong indicator of environmental stress (R2=0.68, p<0.001), as was the wetland-dependent songbird community (R2=0.59, p<0.001). The emergent zone vegetation community was a relatively weak and inconsistent indicator of environmental stress, while the open-water zone vegetation and waterbird communities were poor indicators. To evaluate whether monitoring more than one biotic community provided additional information about a site's biological and environmental condition, we produced a two-taxon IBI that combined wet meadow zone vegetation and wetland-dependent songbird metrics. The two-taxon IBI had a marginally stronger linear relationship to the stress gradient (R2=0.72, p<0.001) than any single biotic community alone, although we argue that this added information would not warrant the extra cost, effort, and logistical barriers of sampling both plants and birds. The wet meadow zone vegetation and wetland-dependent songbird IBIs were strong surrogates of one another (R2=0.57), suggesting that wet meadow zone vegetation can be used to predict the health of wetland-dependent songbirds, and visa versa. Our results suggest that habitat for healthy wet meadow zone vegetation and wetland-dependent songbird communities is being degraded as compensation sites are replacing their natural analogs.

Numerical modeling of drag for flow through vegetated domains and porous structures

In this paper, we study flow through vegetated wetlands using high resolution computational models to describe the flow. The goal is to describe drag characteristics of this flow at the large scales as a function of Reynolds number. This work is of importance to scientists and engineers dealing with wetland health and restoration, inland flooding due to tropical storms and hurricanes, and river lining projects. The existence of vegetation affects the flow resistance, which is a major factor in determining velocity and water level distribution in wetlands.For low Reynolds numbers, wetlands behave similarly to porous media, where it is well-known that Stokes flow at the micro-scale can be upscaled through homogenization to Darcy’s Law at the macro-scale. As Reynolds number increases moderately, small-scale drag effects can be captured by adding a quadratic and/or cubic term to the Darcy equation; the so-called Darcy–Forchheimer model. For higher Reynolds numbers, Stokes equation is no longer a valid approximation, and full Navier–Stokes models must be used. We utilize large eddy simulation (LES) to study vegetative drag at high Reynolds numbers. The numerical simulations in this paper are performed using the Proteus Toolkit, which is under development by Kees and Farthing at ERDC.

适应白洋淀湿地健康评价的IBI方法

适应白洋淀湿地健康评价的IBI方法

Assessing national wetland policies’ portrayal of wetlands: Public resources or private goods?

Despite varying degrees of regulation, policies and standards across different nations, wetlands are consistently being destroyed, devastated and converted to other land uses at a rate more rapid than any other ecosystem. We attempt to understand this disconnection between policy and wetland protection by comparing how wetlands are portrayed in eighteen national wetland policies. It was found that nations with strong-market economies tended to subjectively and objectively characterize wetlands in a vague and indirect fashion; whereas nations with weaker-market economies tended to portray wetlands in a direct and distinct fashion. The results suggest that higher degrees of wetland protection are offered in national policies when wetlands are portrayed as public resources; conversely when wetlands are portrayed as private goods, policies are less apt to provide clear platforms for economic incentives leading to ecosystem-wide protection. Given the state of global wetland health and the alarming trend of global wetland decline, we argue that wetland policy frameworks should portray wetlands as public resources in a direct and prescriptive fashion.

Using 14C and 3H to delineate a recharge ‘window’ into the Perth Basin aquifers, North Gnangara groundwater system, Western Australia

The Gnangara Mound and the underlying Perth Basin aquifers are the largest source of groundwater for the southwest of Australia, supplying between 35 and 50% of Perth's potable water (2009–2010). However, declining health of wetlands on the Mound coupled with the reduction in groundwater levels from increased irrigation demands and drier climatic conditions means this resource is experiencing increased pressures. The northern Gnangara is an area where the Yarragadee aquifer occurs at shallow depths (~50m) and is in direct contact with the superficial aquifer, suggesting the possibility of direct recharge into a generally confined aquifer. Environmental isotopes (14C and 3H) and hydrochemical modelling were used to assess the presence of a recharge ‘window’ as well as understand the groundwater residence time within different aquifers. Forty-nine groundwater samples were collected from depths ranging from 11 to 311m below ground surface. The isotopic variation observed in the superficial aquifer was found to be controlled by the different lithologies present, i.e. quartz-rich Bassendean Sand and carbonate-rich sediments of the Ascot Formation. Rainfall recharge into the Bassendean Sand inherits its dissolved inorganic carbon from the soil CO2. Organic matter throughout the soil profile is degraded by oxidation leading to anoxic/acidic groundwater, which if in contact with the Ascot Formation leads to enhanced dissolution of carbonates. Hydrochemical mass balance modelling showed that carbonate dissolution could contribute 1–2mmolkg−1 of carbon to groundwaters recharged through the Ascot Formation. The corrected groundwater residence times of the Yarragadee aquifer in the northern part of the study area ranged from 23 to 35ka, while waters in the southeastern corner ranged from sub-modern to 2ka. Groundwater ages increase with distance radiating from the recharge ‘window’. This study delineates a recharge ‘window’ into the commonly presumed confined aquifers of the Perth Basin, highlighting the need for appropriate sustainable management.

Mangrove expansion in the Gulf of Mexico with climate change: Implications for wetland health and resistance to rising sea levels

Black mangroves ( Avicennia spp.) are hypothesized to expand their latitudinal range with global climate change in the 21st century, induced by a reduction in the frequency and severity of coastal freezes, which are known to limit mangrove colony extent and individual tree size. The Gulf of Mexico is a prime candidate for population expansion to occur because it is located at the northward limit of black mangrove habitat. This may come at the expense of existing coastal saline wetlands that are dominantly Spartina spp. marsh grasses. The present study was conducted to focus on the implications of a marsh to mangrove transition in Gulf wetlands, specifically: (1) wetland resistance to accelerating eustatic sea level rise (ESLR) rates; (2) resistance to wave attack in large storms (increased cyclonic storm frequency/intensity is predicted with future climate warming); and (3) organic carbon sequestration and wetland soil geochemistry. Field sites of adjacent and inter-grown Avicennia germinans mangrove and Spartina marsh populations in similar geomorphological setting were selected in back-barrier areas near Port Aransas and Galveston, TX. Elevation surveys in the more mature Port Aransas site indicate mangrove vegetated areas are 4 cm higher in elevation than surrounding marsh on an average regional scale, and 1–2 cm higher at the individual mangrove scale. 210Pb and 137Cs accumulation rates and loss on ignition data indicate that mineral trapping is 4.1 times higher and sediment organics are 1.7 times lower in mangroves at Port Aransas. This additional mineral trapping does not differ in grain size character from marsh accumulation. Elevation change may also be effected by soil displacement of higher root volumes in mangrove cores. Port Aransas porosities are lower in mangrove rooted horizons, with a corresponding increase in sediment strength, suggesting mangrove intervals are more resistant to wave-induced erosion during storm events. Port Aransas mangroves exhibit higher pore water redox potentials and salinities over entire core depths and depressed pH over rooted intervals, suggesting a distinct diagenetic environment exists relative to marsh sites. The rooting network, which introduces oxygen into the sediment and focuses evapo-transpiration and salt exclusion within this zone, may prove advantageous when competing with grasses by elevating salinities to levels that are toxic for Spartina. Trends observed in the more mature systems of Port Aransas are generally absent in Galveston, suggesting the youth and physically shorter stature of these systems means they have not yet established a unique sediment signature.

Assessment of wetland ecosystem health in Lower Songkhram, Thailand

A study was conducted to assess the ecosystem health of Lower Songkhram wetland in Thailand, using a newly developed wetland ecosystem health index (WEHI) based on analysis of field survey and secondary data of the most dominant physical, environmental and socio-economic factors extracted by principal components analysis (PCA). The most influential physical, environmental and socio-economic factors identified were rainfall and awareness and participation of the local community, which had positive effects, whereas soil electrical conductivity (EC), biochemical oxygen demand (BOD) and urban development had negative effects. Based on the results, 9 of the 40 land units of the study area were in very good or good health, 11 in reasonable health, while 20 were found to be in poor or even very poor condition. These findings will be useful for decision-makers in planning and executing an effective and holistic strategy to prevent further wetland degradation.

Dispatches

Dispatches

Breeding of the Australasian Bittern (Botaurus poiciloptilus) in New Zealand

In Australasia, wetlands and the birds that inhabit them are under considerable threat. Australasian Bitterns (Botaurus poiciloptilus) are a potential indicator of wetland health but there is an urgent need to collect baseline ecological data and understand processes threatening the species so that conservation actions aimed at reversing apparent declines can be implemented. I collated nest records from New Zealand to determine breeding parameters and highlight areas requiring further research. Nests were recorded throughout the country, and all except one were in wetlands. Booming calls were recorded in most months but peaked between September and November. Breeding was observed from August to May, with most activity in November and December. Nests were in a wide variety of vegetation types, frequently Typha orientalis, and sites were usually surrounded by deep water. Breeding parameters appear similar to those of northern hemisphere species of Botaurus. Australasian Bitterns appear to have a high potential breeding capacity, with large clutches, fairly short incubation periods, and a long breeding season but there are no quantifiable data on nesting success. There are major gaps in our knowledge, and research on breeding should focus on assessing the fate of breeding attempts, potential influence of habitat loss and fragmentation on breeding success, vulnerability to predation by introduced mammals, the interaction between predation risk and water levels, and the roles of food and habitat in sustaining populations.

Use of ecological indicators to assess the quality of Great Lakes coastal wetlands

Over 2000 coastal wetland complexes have been identified in the Laurentian Great Lakes watershed, each providing critical habitat for numerous aquatic and terrestrial species. Research has shown there is a direct link between anthropogenic activities (urbanization and agricultural development) and deterioration in wetland health in terms of water quality and biotic integrity. In this study, we evaluate coastal marshes throughout the Great Lakes basin using a suite of published ecological indices developed specifically for coastal wetlands of the Great Lakes (Water Quality Index (WQI), Wetland Macrophyte Index (WMI), and the Wetland Fish Index (WFI Basin)). We surveyed 181 wetlands, including 19 in Lake Superior (11%), 11 in Lake Michigan (6%), 13 in Lake Huron (7%), 92 in Georgian Bay and the North Channel (51%), 18 in Lake Erie (10%), and 28 in Lake Ontario (15%), over a 13 year period (1995–2008). Water quality parameters were measured at every site, while paired fyke nets were used to assess the fish community (132 sites) and macrophytes were surveyed and identified to species (174 sites); all of this information was used to calculate the associated index scores. One-way ANOVA results showed that there were significant differences in wetland quality among lakes. According to the WQI, we found that over 50% of marshes in Lakes Michigan, Erie, and Ontario were in degraded condition, while over 70% of marshes in Lakes Superior, Huron, and Georgian Bay were minimally impacted. Georgian Bay had the highest proportion of wetlands in very good and excellent condition and least number of wetlands in a degraded state. The WMI and WFI showed similar results. This is the largest bi-national database of coastal wetlands and the first study to provide a snapshot of the quality of coastal habitats within the Great Lakes basin. We recommend this information be used to guide conservation and restoration efforts within the Laurentian Great Lakes.

Environmental Impact of Long Piers on Tidal Marshes in Maryland-Vegetation, Soil, and Marsh Surface Effects

Piers may impact the health of coastal wetlands by altering vegetation, soil organic matter accretion, and sediment deposition or erosion. Permit requests for piers have recently increased in the U.S. leading to concern by environmental regulatory agencies on potential impacts. In response, a project was conducted in Maryland to assess the impacts of long piers on plant communities, soils, and marsh surface characteristics. Twenty sites with piers and 20 control sites were assessed. Control sites and pier sites were similar with respect to soil types, marsh surface characteristics, and plant community composition. Shading consistently reduced vegetation density directly beneath piers and occasionally reduced vegetation density adjacent to piers. Shading favored Spartina alterniflora over Distichlis spicata, and Distichlis spicata over Spartina patens. Distribution of marsh surface components (high marsh, low marsh, mudflats, open water) was unaffected by proximity to piers. Direct evidence of pier effects on erosion or deposition was limited to the immediate vicinity of a few piers. In general, thickness of the organic horizons or that of the root mats was unaffected by proximity to a pier. We concluded that any effects of piers on vegetation or erosion were restricted to the close proximity of the piers.

Human impacts on hydrological health and the provision of ecosystemservices: a case study of the eMthonjeni–Fairview Spring Wetland, Grahamstown, South Africa

Wetland hydrological health and the provision of indirect ecosystem services in the eMthonjeni–Fairview Spring Wetland, Grahamstown, South Africa, were assessed in 2008, using the newly developed wetland assessment tools WET-Health and WET-EcoServices. Variation in health and ecosystem services were assessed over time, based on aerial photograph interpretation and the use of the score sheets in these assessment tools. Hydrological health and indirect ecosystem services of the wetland have been altered since 1949, due to human activities both in the catchment and the wetland. The most significant human intervention on the wetland's hydrological health was the result of road construction and invasion by alien plants. Water use by local residents had an unmeasurable effect on hydrological health. Wetland health is related to the provision of wetland ecosystem services, and cumulative impacts in the catchment and wetland have reduced the provision of many indirect wetland ecosystem services.

Hydrologic and mechanical control for an invasive wetland plant, Juncus ingens, and implications for rehabilitating and managing Murray River floodplain wetlands, Australia

Wetlands are prone to increased invasion by plant species following changes in hydrologic regime, leading to shifts in plant community composition and potentially ecosystem function and health. In this paper, the ecology and potential control of Juncus ingens, a native wetland plant in the Murray-Darling Basin of south-eastern Australia, is investigated. J. ingens has benefited from altered Murray River hydrologic conditions by expanding its range and invading seasonally-flooded grassland and riparian habitats along the Murray River. Here results of complementary glasshouse and field research of seedling and mature J. ingens growth and resilience as influenced by hydrologic regime (moist, saturated, partial inundation and when possible, complete inundation) and mechanical control (i.e., clipping) are presented. A moist hydrologic regime (soil held at field capacity) resulted in the most vigorous seedlings (13.9–73.0% more total biomass), while saturated conditions (flooding maintained level with the soil surface) resulted in the most vigorous mature J. ingens (14.1–98.4% more total biomass). Seedling mortality was greatest under complete and prolonged inundation (60% fatal with remaining 40% showing severe stress), conditions suspected to have limited prior invasion but which currently occur infrequently as a result of reduced flooding magnitude. Clipping was fatal for nearly all seedlings regardless of hydrologic regime but was only fatal for mature plants if coupled with prolonged inundation. Coupling ground-level clipping with strategic flooding may be the most effective means for controlling current populations of J. ingens and limiting further invasion, promoting re-colonisation by displaced species and rehabilitating the health of Barmah Forest and similar Murray River floodplain wetlands.

Using ecological indices to measure economic and environmental performance of irrigated agriculture

Growing public concern about the health of rivers and wetlands, and the ecosystems they support, puts pressure on large water users–such as the irrigation industry–to find ways to use less water. At the same time, the growing competitiveness of the economic environment places demands on the industry to maintain its productivity and profitability. This study develops a method, based on the concept of an environmental performance index ( EPI), to measure the economic and environmental performance of irrigated agricultural enterprises. In defining environmental pressure exerted by the irrigation industry the method incorporates certain characteristics of ecological assets affected by water withdrawal for irrigation. As an empirical application, the method was applied to a case study of seventeen natural resource management (NRM) regions within the Murray–Darling Basin (MDB), Australia. Data Envelopment Analysis was used to compute the component distance functions in order to construct an EPI for each considered irrigated enterprise in each NRM region. The results of the analysis show that environmental efficiencies of irrigated enterprises vary considerably across NRM regions. These findings support the case for policy targeting by type of irrigation enterprise and by location of enterprises.

Healthy Evaluation for Wetlands Based on Vague Mathematics: Taking the wetlands on Laizhou Bay′s Coastal Plain of China as a case

Taking the wetlands on Laizhou Bay′s Coastal Plain of Shandong Province of China,this paper evaluated the health of the wetland by using vague mathematics method. The connotation and correlative theories of wetland health were first expatiated here. According to interrelated fundamental, the paper selected twenty three indexes from the ecological character, unitary function and the society environment of the wetland, and then established an indicator system for ecosystem health evaluation of wetland on coastal plain of Laizhou Bay. The indicator system includes monomial index, subtype index and composite index, and each index measures off four grades according to corresponding standard, the grades are excellent health, health, subhealth and illness. The paper established subject degree of each grade for each index and formatted matrix of judgment, and also formatted the right weight vector of each index by referring to the opinion of experts, and ultimately evaluated the health of wetland ecosystem on coastal plain of Laizhou Bay by using two-grad fuzzy comprehensive judging model. In view of the evaluation results some illness factors of the wetland were discussed in the end.

Relative importance of macrophyte community versus water quality variables for predicting fish assemblages in coastal wetlands of the Laurentian Great Lakes

Fish have been shown to be sensitive indicators of environmental quality in Great Lakes coastal wetlands. Fish composition also reflects aquatic macrophyte communities, which provide them with critical habitat. Although investigators have shown that the relationship between water quality and fish community structure can be used to indicate wetland health, we speculate that this relationship is a result of the stronger, more direct relationship between water quality and macrophytes, together with the ensuing interconnection between macrophyte and fish assemblages. In this study, we use data collected from 115 Great Lakes coastal marshes to test the hypothesis that plants are better predictors of fish species composition than is water quality. First we use canonical correspondence analysis (CCA) to conduct an ordination of the fish community constrained by water quality parameters. We then use co-correspondence analysis (COCA) to conduct a direct ordination of the fish community with the plant community data. By comparing the statistic ‘percent fit,’ which refers to the cumulative percentage variance of the species data, we show that plants are consistently better predictors of the fish community than are water quality variables in three separate trials: all wetlands in the Great Lakes basin (whole: 21.2% vs 14.0%; n = 60), all wetlands in Lakes Huron and Superior (Upper: 20.3% vs 18.8%; n = 32), and all wetlands in Georgian Bay and the North Channel (Georgian Bay: 18% vs 17%; n = 70). This is the largest study to directly examine plant–fish interactions in wetlands of the Great Lakes basin.

Simulating urban expansion by coupling a stochastic cellular automata model and socioeconomic indicators

Urbanization is one of the most important anthropogenic activities that create extensive environmental implications at both local and global scales. Dynamic urban expansion models are useful tools to understand the urbanization process, project its spatiotemporal dynamics and provide useful information for assessing the environmental implications of urbanization. A hybrid urban expansion model (NNSCA model) was proposed to simulate rapid urban growth in a typical industrial city, Dongying, China, by coupling a artificial-neural-network-based stochastic cellular automata model and several socioeconomic indictors, i.e., the per capita income of the rural population, the per capita income of the urban population, population and gross domestic products of the city. Good conformity between simulated and actual urban patterns suggested that the NNSCA model was able to effectively simulate historic urban growth and to generate realistic urban patterns. A series of scenario analyses suggested that the expanding urban would threaten the ecosystem health of coastal wetlands in the city unless environmental protection actions are taken in the future. The NNSCA model provides abilities to assess future urban growth under various planning and management scenarios, and can be integrated into ecological or environmental process models to evaluate urbanization’s environmental implications.

Monitoring of aquatic macroinvertebrates as bioindicator for assessing the health of wetlands: A case study in the Central Himalayas, India

Abstract The present contribution encompasses the first case study on the aquatic macroinvertebrates as bioindicators for assessing the health of Asan wetland (area 3.2 km 2 ), located in the foothills of Central Himalayas, India. Monthly sampling from all the sampling sites in five replicates was made for a period of 12 months (July 2002–June 2003) at 9:00–11:00 h. A total of 32 species of macroinvertebrates were found with the Ephemeroptera and Gastropoda being the most abundant component of invertebrates communities. The Shannon–Wiener diversity index calculated for macroinvertebrates ranged from 3.50 to 4.61. Seasonal fluctuations in the density of macroinvertebrates revealed maximum density (451–503 ind m −2 ) during winter and minimum (126–143 ind m −2 ) during monsoon season. The density of macroinvertebrates was influenced by the anthropogenic disturbances and water level fluctuations causing disturbance in the littoral zone of the wetland. The statistical relationships between turbidity, transparency, dissolved oxygen and water temperature and macroinvertebrates of Asan wetland were also computed for assessing the impact of anthropogenic disturbances on macroinvertebrates.

Application of a Vegetation-Based Index of Biotic Integrity for Lake Erie coastal marshes in Ohio

Substantial effort in recent years has been invested in developing monitoring protocols and indicators for assessing the health of coastal wetlands of the Great Lakes. Most efforts have collected data exclusively in Great Lakes coastal wetlands and have not evaluated coastal wetland indicator development in the context of other wetland types in the state, province, or region. “Inland” freshwater wetlands are also subject to multiple hydrologic cycles of differing time scales and in some landscape contexts may be as hydrologically variable as Great Lakes coastal wetlands. The Ohio Environmental Protection Agency developed a Vegetation Index of Biotic Integrity (VIBI) for wetlands based on vascular plants as the indicator taxa group. The extension of the VIBI to Lake Erie coastal marshes was evaluated. Least-impacted Lake Erie marshes did not have significantly lower (or higher) scores (p &amp;lt; 0.001) although the upper 75th percentile of coastal wetland scores was not as high as the upper 75th percentile of inland wetland VIBI scores. Significant correlations (p &amp;lt; 0.01) were observed with two different human disturbance gradients in a combined data set of inland and coastal wetlands. Simultaneous metric evaluation using Principal Components Analysis showed some separation in metric performance between inland and coastal wetlands but also clear overlap, especially between reference-quality inland and coastal systems. Ordination of species presence and abundance data revealed similar patterns with some separation between inland and coastal wetlands but considerable overlap in species composition. Lake Erie coastal marshes represent another type of emergent marsh system. With minor modifications, the VIBI, developed with inland wetland data sets, worked well for assessing Lake Erie coastal wetlands in Ohio. The analysis of data from Ohio coastal wetlands with a larger inland reference data set shows the advantages of treating Great Lakes coastal wetlands as a type of freshwater wetland and working toward indicator development in the context of an overall state or provincial wetland classification and assessment program.

Local and Landscape Influence on Red-winged Blackbird ( Agelaius phoeniceus) Nest Success in Great Lakes Coastal Wetlands

Nest predation has been identified as the primary mechanism contributing to reduction of reproductive success for the marsh-breeding red-winged blackbird ( Agelaius phoeniceus). Differences in rates of nest predation have been linked to nest site characteristics within a wetland, primarily water depth. However, the relationship between the landscape surrounding these habitats and the probability of nest predation is uncertain. Moreover, factors associated with reproductive success could be a potentially powerful indicator of ecological condition in wetland habitats. We investigated the influence of landscape pattern on nest success by monitoring 366 red-winged blackbird nests in 11 coastal wetlands along the south shore of Lake Superior. Of the 366 nests, 39% were successful, 56% failed, and 5% were abandoned or lacked sufficient evidence to determine nest fate. Nest predation accounted for over 93% of total failures. Predation rates ranged from 31% to 97% among the 11 wetland sites. We modeled nest predation using multi-model logistic regression analysis and the Akaike information criterion to identify and parameterize influential variables derived from the nest site, wetland, and landscape surrounding each wetland. Our results indicated that landscape variables comprised over 50% of model prediction weight in 15 of the 17 models. Nest failure was highest at sites within an urban/residential landscape matrix. Reproductive success could be a good indicator of the ecological health of Great Lakes wetlands.