Open Water Wetlands Research Articles

Removal of nutrients, trace organic contaminants, and bacterial indicator organisms in a demonstration-scale unit process open-water treatment wetland

A demonstration-scale unit process open-water wetland system was built to treat water from an effluent-dominated river (i.e., a river in which the flow consisted almost entirely of municipal wastewater effluent from May to October). Monitoring of the system over a two-year period indicated effective removal of nitrate, with concentrations decreasing by over 90% during summer. The temperature-independent areal first-order nitrate removal rate constant, k20, ranged from 61.7 to 68.1myr−1 after the microbial community was established, which is significantly higher than values typically observed in full-scale surface flow wetlands. The beta-adrenergic blockers, atenolol and propranolol, as well as the antiviral drug, acyclovir, were removed by photolysis and biotransformation in the wetland biomat, whereas the antiepileptic drug, carbamazepine, exhibited little removal. The bacterial indicators E. coli and enterococci decreased substantially during summer, mainly through sunlight exposure. Models of contaminant removal based upon measured flow rates and performance data collected at a similar pilot-scale system agreed well with measured data for nitrate and the trace organic contaminants. The model accurately predicted removal of enterococci but systematically over-predicted the removal of E. coli. During the two-year study period, routine maintenance was necessary to prevent colonization of the water surface with duckweed (Lemna spp.). Unit process open-water (UPOW) wetlands may offer a low-cost means of improving water quality in natural treatment systems that can be integrated with conventional surface-flow wetlands and other managed natural systems. The quantitative models of contaminant removal described in this study can be used to design natural treatment systems that balance the needs for local water quality requirements, available land and site-specific requirements.

Habitat selection and activities of dabbling ducks during non‐breeding periods

ABSTRACTWestern Tennessee is an important region for waterfowl during non‐breeding periods, supporting >40% of the Mississippi Flyway population of American black ducks (Anas rubripes). Understanding habitat selection and activities of waterfowl during the non‐breeding period is important for directed habitat management on national wildlife refuges and in other wetlands important in meeting regional waterfowl conservation objectives. During November–February 2011–2013, we investigated diurnal habitat selection and activities of dabbling ducks (Anatini) among 5 common wetland types relative to emergent cover, water depth, and energetic carrying capacity (i.e., duck energy days [DEDs]) in western Tennessee, USA. We observed waterfowl daily and sampled food resources monthly at Tennessee and Cross Creeks National Wildlife Refuges. Mallard (Anas platyrhynchos), gadwall (A. strepera), northern pintail (A. acuta), and American green‐winged teal (A. carolinensis) selected moist‐soil wetlands over wooded, aquatic bed, and open water wetland types. Gadwall also selected deeper wetlands containing submersed aquatic vegetation. Foraging was the dominant activity of all dabbling ducks in mudflats and moist‐soil wetlands, and it was also dominant in wooded wetlands for green‐winged teal and gadwall. Deep, open water was avoided by dabbling ducks. Selection of wetland types was negatively correlated with increasing water depth and positively correlated with increasing emergent cover and DEDs. Shallowly flooded moist‐soil and wooded wetlands provide high‐energy foods and dense emergent cover, and are important to a diversity of dabbling ducks during winter. © 2017 The Wildlife Society.

Controls on plot-scale evapotranspiration from a constructed fen in the Athabasca Oil Sands Region, Alberta

In the Athabasca Oil Sands Region of the Western Boreal Plain mining companies now recognize the importance of reclaiming peatlands, as they cover >50% of the pre-mined regional landscape. To date, reclamation efforts have focused on marsh and open water wetlands. However, these wetland systems are not abundant in the sub-humid climate of the WBP because of their excessive evapotranspiration (ET) losses, compared to peatland wetlands. The experimental Nikanotee Fen was constructed as part of the landscape reclamation, engineered with the intent to support natural fen vegetation and hydrologic processes. The influences of vegetation and treatment types on plot-scale energy fluxes and ET demands were examined over the 2014 growing season, one year post-construction. Actual ET and environmental variables, such as water table, soil moisture, temperature and relative humidity, were monitored in thirty-one study plots comprising control, moss and seedling plots (with and without wood-strand mulch), as well as three ponds. Actual ET was measured with weighing lysimeters and used to correct equilibrium ET, calculated using the Priestley-Taylor combination method. A roaming meteorological station was instrumented to quantify and compare available energy over different cover types. Modeled plot-scale ET was validated against continuously measured eddy covariance ET values. Cumulative ET exceeded precipitation in all plot types with average rates of 4.4, 3.2, 3.9 and 2.8mm/day from open water, control, seedling and moss plots, respectively. Mulch reduced ET rates in both seedling and moss plots, where moss-mulch plots showed the lowest rates (2.4mm/day). The presence of mulch lowered the near-surface vapour pressure deficit, thus providing a more favorable microclimate for moss establishment by elevating near-surface relative humidity and reducing air and soil temperature by ∼2°C. Although vapour pressure deficit did not significantly control ET (p>0.05), mulch appeared to have a greater influence on ET in moss plots than seedling plots. Water table position displayed a weak yet significant (p<0.05) control on ET in seedling plots. As these reclamation practices have not yet been well tested in the Alberta oil sands region; this study provides recommendations to reduce evaporative stress and aid in the establishment of functioning constructed peatland ecosystems.

English

This study assessed the current status of Awoja in Ngora district of Eastern Uganda.&nbsp; Remote sensing, household survey, In Pac S methodology and focus group discussions were used to acquire data from April to July, 2015.&nbsp;&nbsp; Landsat satellite imageries from 2007 and 2013 were acquired by USGS Earth Explorer to quantify land use/cover changes.&nbsp;&nbsp; Five land use/cover types were identified namely; (1) open water (2) wetland (3) tree cover (4) agriculture and (5) built up area.&nbsp; The findings indicate a fivefold increase in built up area by 154.27Km2 and open water changed by 8.7 Km2 and a reduction in wetland area by -1.0Km2&nbsp; tree cover by -48.07Km2 and agriculture area by -11.4.0Km2. The survey results indicated deforestation, wetland encroachment, poor attitude and over population as the main reasons for degradation. In Pac S methodology findings showed convergence in the perceived indicator of degraded watershed in terms of water and soil quality; vegetation type and species diversity among the lay people and technocrats. The focus group discussion findings indicated a negative trend in land use/cover change.&nbsp; There is need for a concerted effort to design an appropriate restoration strategy for Awoja. &nbsp; Key words: Land use/cover, remote sensing, GIS and other methods.

Vegetation alters the effects of salinity on greenhouse gas emissions and carbon sequestration in a newly created wetland

Wetland creation or restoration in degraded areas has become a new type of disturbance worldwide. Coastal wetlands serve a vital role in global carbon cycles; thus, it is important to understand the impacts of wetland creation on carbon storage functions. Carbon emissions and accumulation in wetlands are reported to be highly site-specific depending on factors such as salinity, plant type and productivity, and water table. This study investigated the effects of different salinities (<2‰, ∼5‰ and >10‰) on greenhouse gas emissions and carbon sequestration of created wetlands in the Yangtze River estuary. CH4 emissions significantly declined with increasing salinity, likely because of the higher sediment sulfate content at higher salinities. CO2 emissions were highest at intermediate salinities (∼5‰). In unvegetated sites, the absolute CO2 emission equivalent was 0.178kgm−2y−1 in the <2‰ salinity treatment, which was 8.09 times higher than the >10‰ salinity treatment. In vegetated sites, the <2‰ salinity treatment had the highest annual net flux of carbon. Thus, despite the high carbon emission of low salinity wetland, enhanced plant productivity resulted in a high carbon absorption rate. Overall, these results demonstrate that the presence of vegetation altered the effects of salinity on carbon equivalency in created wetlands. This study suggests that to conserve the wetland carbon sink function, landscape design for wetland restoration in estuarine regions should consider creating open water wetland in high salinity regions and restoring vegetation in low salinity regions to facilitate the growth of macrophytes such as Phragmites australis.

Avian Communities of the Northern Mackenzie Mountains, Northwest Territories, Canada

Basic knowledge of the abundance and distribution of birds and their habitats and the relationships between them is limited for many parts of Arctic Canada, including montane regions. This information is important for conservation purposes as bird populations and habitats shift and as interest in development of northern areas increases. We characterized bird communities in the Mackenzie Mountains of the Northwest Territories by conducting point counts (n = 376) in June 2009 and 2010 and using community analysis metrics (multiple response permutation procedures, indicator species analysis, non-metric multidimensional scaling) to statistically and graphically describe bird data in six habitat types: coniferous forest, deciduous forest, shrub (short and tall), alpine tundra, and open water wetlands. Distinct habitats had significantly different bird communities, as shown by using multiple response permutation procedures (p &lt; 0.005). Of 51 species, 32 had significant (p &lt; 0.05) indicator values for one habitat type (n = 15) or groups of habitats (n = 17) in an indicator species analysis. The tall shrub habitat type had the most indicator species (six species) followed by alpine tundra (five species), then the combined conifer, deciduous, and wetland habitat group (four species) and the deciduous forest habitat types (three species). Species richness was highest in the tall shrub (n = 37), alpine (n = 30), and conifer and short shrub (n = 29) habitats. We also observed eight bird species not previously known to occur in the area, or which were outside published ranges. Our results highlight the variability in bird community composition between the major habitat types in the Mackenzie Mountains, serve as a baseline for future bird studies in the region, and underscore the need for more research in the area with impending anthropogenic changes.

Sunlight inactivation of fecal indicator bacteria in open-water unit process treatment wetlands: Modeling endogenous and exogenous inactivation rates

A pilot-scale open-water unit process wetland was monitored for one year and found to be effective in enhancing sunlight inactivation of fecal indicator bacteria (FIB). The removal of Escherichia coli and enterococci in the open-water wetland receiving non-disinfected secondary municipal wastewater reached 3 logs and 2 logs in summer time, respectively. Pigmented enterococci were shown to be significantly more resistant to sunlight inactivation than non-pigmented enterococci. A model was developed to predict the inactivation of E. coli, and pigmented and non-pigmented enterococci that accounts for endogenous and exogenous sunlight inactivation mechanisms and dark processes. Endogenous inactivation rates were modeled using the sum of UVA and UVB irradiance. Exogenous inactivation was only significant for enterococci, and was modeled as a function of steady-state singlet oxygen concentration. The rate constants were determined from lab experiments and an empirical correction factor was used to account for differences between lab and field conditions. The model was used to predict removal rate constants for FIB in the pilot-scale wetland; considering the variability of the monitoring data, there was general agreement between the modeled values and those determined from measurements. Using the model, we estimate that open-water wetlands at 40° latitude with practical sizes can achieve 3-log (99.9%) removal of E. coli and non-pigmented enterococci throughout the year [5.5 ha and 7.0 ha per million gallons of wastewater effluent per day (MGD), respectively]. Differences in sunlight inactivation rates observed between pigmented and non-pigmented enterococci, as well as between lab-cultured and indigenous wastewater bacteria highlight the challenges of using FIB as model organisms for actual pathogens in natural sunlit environments.

Sunlight inactivation of viruses in open-water unit process treatment wetlands: modeling endogenous and exogenous inactivation rates.

Sunlight inactivation is an important mode of disinfection for viruses in surface waters. In constructed wetlands, for example, open-water cells can be used to promote sunlight disinfection and remove pathogenic viruses from wastewater. To aid in the design of these systems, we developed predictive models of virus attenuation that account for endogenous and exogenous sunlight-mediated inactivation mechanisms. Inactivation rate models were developed for two viruses, MS2 and poliovirus type 3; laboratory- and field-scale experiments were conducted to evaluate the models' ability to estimate inactivation rates in a pilot-scale, open-water, unit-process wetland cell. Endogenous inactivation rates were modeled using either photoaction spectra or total, incident UVB irradiance. Exogenous inactivation rates were modeled on the basis of virus susceptibilities to singlet oxygen. Results from both laboratory- and field-scale experiments showed good agreement between measured and modeled inactivation rates. The modeling approach presented here can be applied to any sunlit surface water and utilizes easily measured inputs such as depth, solar irradiance, water matrix absorbance, singlet oxygen concentration, and the virus-specific apparent second-order rate constant with singlet oxygen (k2). Interestingly, the MS2 k2 in the open-water wetland was found to be significantly larger than k2 observed in other waters in previous studies. Examples of how the model can be used to design and optimize natural treatment systems for virus inactivation are provided.

Biotransformation of trace organic contaminants in open-water unit process treatment wetlands.

The bottoms of shallow, open-water wetland cells are rapidly colonized by a biomat consisting of an assemblage of photosynthetic and heterotrophic microorganisms. To assess the contribution of biotransformation in this biomat to the overall attenuation of trace organic contaminants, transformation rates of test compounds measured in microcosms were compared with attenuation rates measured in a pilot-scale system. The biomat in the pilot-scale system was composed of diatoms (Staurosira construens) and a bacterial community dominated by β- and γ-Proteobacteria. Biotransformation was the dominant removal mechanism in the pilot-scale system for atenolol, metoprolol, and trimethoprim, while sulfamethoxazole and propranolol were attenuated mainly via photolysis. In microcosm experiments, biotransformation rates increased for metoprolol and propranolol when algal photosynthesis was supported by irradiation with visible light. Biotransformation rates increased for trimethoprim and sulfamethoxazole in the dark, when microbial respiration depleted dissolved oxygen concentrations within the biomat. During summer, atenolol, metoprolol, and propranolol were rapidly attenuated in the pilot-scale system (t1/2 < 0.5 d), trimethoprim and sulfamethoxazole were transformed more slowly (t1/2 ≈ 1.5-2 d), and carbamazepine was recalcitrant. The combination of biotransformation and photolysis resulted in overall transformation rates that were 10 to 100 times faster than those previously measured in vegetated wetlands, allowing for over 90% attenuation of all compounds studied except carbamazepine within an area similar to that typical of existing full-scale vegetated treatment wetlands.

Community congruence of plants, invertebrates and birds in natural and constructed shallow open-water wetlands: Do we need to monitor multiple assemblages?

Biomonitoring is a common means of evaluating wetlands. It is based on the premise that the community composition of one taxonomic group is indicative of overall biology and the underlying environmental conditions at a wetland. To be a good bioindicator, there must be adequate concordance between the indicator group and other biotic assemblages. Otherwise, multi-assemblage monitoring is necessary to glean a complete picture of wetland condition. In 32 sites ranging from reference wetlands to stormwater retention ponds, we evaluated concordance in community composition among the six most commonly monitored wetland assemblages: waterfowl, wetland dependent songbirds, aquatic macroinvertebrates, and plants in the wet meadow, emergent, and open-water vegetation zones. We also assessed agreement in environmental correlates among these six assemblages and investigated the impact of human disturbance on cross-assemblage concordance. We found that cross-assemblage concordance was positive (p<0.03 in 14 of 15 pair-wise comparisons, p=0.06 in 15th case), but relatively low (Mantel R values 0.11–0.37), suggesting that the assemblages are mediocre surrogates for one another. Yet, we found very strong agreement among environmental correlates of the six assemblages, especially along the first axis of assemblage-specific ordinations (mean Spearman rho=0.923), indicating that despite low concordance, the six assemblages are likely responding to the same environmental gradients. Thus, while a single assemblage may not serve as a surrogate for the other assemblages, it should yield an adequate estimate of underlying environmental conditions and the degree of disturbance. Most important among the environmental correlates were sediment and water nutrient levels, shoreline slope, and the size of wet meadow and emergent vegetation zones. Perhaps most interestingly, we found that the strength of cross-assemblage concordance was greatest in reference wetlands and was lower (p≤0.05) in constructed wetlands. This implies that cross-assemblage concordance present in undisturbed sites may not persist in disturbed wetlands where several of these cross-assemblage relationships deteriorate. Furthermore, a general change in cross-assemblage concordance may itself be indicative of human disturbance in wetlands.

Methane emissions from riverine and swampy coastal wetlands: influence of open and macrophyte‐infested areas

The atmospheric concentration of methane (CH4) exerts a strong influence on the global climate. Notably, wetlands are important CH4 sources, whose emission represents an ecosystem process depending on such wetland characteristics as organic matter, temperature, pH, methanogenesis and CH4 oxidation, all of which vary on the basis of the type of wetland. Methane fluxes were investigated in a preliminary study in the region, using the chamber method in the open water and macrophyte-infested wetlands of swampy and riverine types in Kilifi, a coastal district in Kenya, Africa. Despite a lack of significant interactions, the macrophyte-infested areas emitted the highest quantity of methane of about 21.96 ± 0.04 mg CH4 m−2 day−1, compared with the water areas that emitted about 19.35 ± 0.05 mg CH4 m−2 day−1. The preliminary CH4 fluxes measured in this study are below the range reported from previous wetland field experiments in the tropics and temperate regions, indicating the need to conduct a series of similar experiments to produce more precise total estimates in the entire region.

Plant community, environment, and land-use data from oil sands reclamation and reference wetlands, Alberta, 2007–2009

Our goal was to evaluate the success of wetland reclamation efforts on oil sands mining company lease-holdings in Alberta, Canada. Already, 60 200 ha of land have been disturbed by mining, and an additional 419 800 ha will be mined in the future. Wetland reclamation efforts have been underway for 35 years, and current mine closure plans call for the construction of 15 840 ha of wetland habitat. There are, however, no accepted criteria by which the Alberta Government can evaluate constructed wetlands. We employed the reference condition approach, comparing reclamation wetlands to appropriate natural analogues with plants as bioindicators of wetland condition. The data set includes 74 wetlands, spanning a range in salinity, nutrient levels, size, and degree of human disturbance. Reclamation wetlands include those contaminated with oil sands tailings (oil sands process affected, OSPA, n = 13) and those free from tailings (oil sands reference, OSREF, n = 12). In contrast, some natural wetlands are exposed to agricultural impacts (AG, n = 12), but the majority represent our least-disturbed condition (reference wetlands, REF, n = 37). The data set includes species relative abundance from plant communities in the wet meadow, emergent, and open-water vegetation zones. In addition, we measured water and sediment chemistry variables and physical variables to quantify local environmental conditions. We also quantified land use surrounding 45 of the wetlands in a series of nested buffers ranging from 300 m to 2000 m from the edge of each wetland's open-water zone. This data set represents the most comprehensive, publicly available data on reclamation wetlands from the lease areas of the two largest oil sands mining companies. It may be used to investigate changes in wetland plant community composition along both natural and human-caused environmental gradients, including contamination by oil sands mine tails. The data could also inform studies into the effects of surrounding land use on wetland plants and local-level environmental conditions. Information about reclamation wetlands could serve as a basis for tracking reclamation trajectories over time, whereas information about reference wetlands could be used to characterize natural variability in plant communities in shallow open-water wetlands from the Boreal Plains ecoregion.

Relative influence of local- and landscape-level habitat quality on aquatic plant diversity in shallow open-water wetlands in Alberta’s boreal zone: direct and indirect effects

Reclamation usually involves modification of the local environment to achieve some biotic target, but if the influence of Landscape Condition on that target is great, we may fail to meet it despite efforts at the local-level. We sought to determine the relative influence of local- and landscape-level habitat on aquatic plant diversity in shallow open-water wetlands. Furthermore, we asked whether the influence of Landscape Condition should be attributed to direct (dispersal-related) effects, or to the indirect effect of landscape variables that influence local habitat quality. Finally, we asked if spatial scale (300–2000 m) would affect conclusions about the relative influence of local- and landscape-level effects. Using structural equation modeling, we found that Local Condition is consistently more influential than Landscape Condition. As landscape size increases, the relative importance of Landscape Condition declines and there is a trade-off between its direct and indirect components. At ≤500 m direct landscape effects were of greater importance than indirect effects, whereas indirect effects of Landscape Condition became more important at ≥1500 m. This suggests that the dominant mechanism by which land use influences diversity depends on the spatial extent of the landscape. We recommend that reclamation designs include a high proportion of wetland habitat and incorporate seeding/planting if diverse plant communities are desired. Additionally, we note that the influence of the landscape is strongest within 300 m. Thus, the focus of reclamation efforts should remain at the in-lake level and the immediate surroundings: this is where efforts will achieve the greatest effect on aquatic plant diversity.

A survey of hydrological changes to wetlands of the Murrumbidgee River

The Floodplain (1974 flood height) of the Murrumbidgee River between Wagga Wagga and Hay Weir in New South Wales encompasses 174,700 ha. In this study area, open water wetlands occupy 2,005 ha and red river gum wetlands occupy 47,075 ha. A total of 570 ha of the red river gum has been killed by increased inundation. Fifty one percent of the open water wetlands (62% of total area) have been affected by local hydrological change. Water levels in 11% of open water wetlands (24% of total area) are now heavily controlled, and 31% (36% of total area) have been made permanent. the water regimes of Murrumbidgee wetlands are less altered that those of Murray River wetlands, but their extent of local hydrological control is similar to wetlands of the Namoi River. Future wetland surveys should record the degree and type of control of their water regimes.

التغيرات البيئيه للمسطحات المائيه في جنوب العراق إعتمادا على الدراسات البالينولوجيه

Palynological techniques are useful in reconstructing past environments, especially when other sources of information are lacking. We have embarked on a palynological study of the wetlands in Southern Iraq in an attempt to determine the nature and extent of past plant communities and other conditions prior to the drying of the wetland in the 1990s. Ten 1-m depth cores were collected from selected locations in marshes and shallow open water wetlands in Mesopotamian wetlands of Southern Iraq. Pollen diagrams from three short cores from the Hawizeh wetlands serve as a reference because this site has not been drained. The palynomorphs in these cores were Gramineae, Chenopodiaceae, Typha, Isonandra lanceolata, Bursarea, Artocarpus, Ireantea, Arenga, Crinum, Palmae, Navia, Tofieldia, Ipomorea, Xyris, and Morus. Fungal spores including Polyporisporites, Pluricellaesporites palyadosporites, Fusiformisporites, Spegazzinites indicus, Diporisporites, Plochmopellinites, Lycoperdon, Miliolinites, Dryadosporites constrictus, and Trichothyrites padapakarensis were noteworthy. Charcoal was scattered through the cores and indicate activities associated with human settlements. Many other forms of cuticles, filaments, insects, algae, and foraminifera test linings were also recorded. A second set of pollen samples were analyzed from 160 soil samples from eight cores collected from the wetland area which was dried during the 1990s. These data show a mixture of pollen and spores that could be used to evaluate past vegetation, climatic, and ecological changes. Preliminary results indicated that chenopodiaceous have increased while germinate types have declined which probably reflected desertification and a trend towards a more aeolian landscape during the 1990s. It is hoped that these studies will be useful in establishing conditions of the wetlands prior to destruction and will assist in setting restoration goals in the future. Case studies of one deep borehole (153 m) near Amara city for evaluating late Quaternary history and dig of 3 m depth to evaluate ancient desertification by wetland dryness were taken for correlation and connection with this recent sediment.

Remote Sensing and Wetland Ecology: a South African Case Study.

Remote sensing offers a cost efficient means for identifying and monitoring wetlands over a large area and at different moments in time. In this study, we aim at providing ecologically relevant information on characteristics of temporary and permanent isolated open water wetlands, obtained by standard techniques and relatively cheap imagery. The number, surface area, nearest distance, and dynamics of isolated temporary and permanent wetlands were determined for the Western Cape, South Africa. Open water bodies (wetlands) were mapped from seven Landsat images (acquired during 1987 – 2002) using supervised maximum likelihood classification. The number of wetlands fluctuated over time. Most wetlands were detected in the winter of 2000 and 2002, probably related to road constructions. Imagery acquired in summer contained fewer wetlands than in winter. Most wetlands identified from Landsat images were smaller than one hectare. The average distance to the nearest wetland was larger in summer. In comparison to temporary wetlands, fewer, but larger permanent wetlands were detected. In addition, classification of non-vegetated wetlands on an Envisat ASAR radar image (acquired in June 2005) was evaluated. The number of detected small wetlands was lower for radar imagery than optical imagery (acquired in June 2002), probably because of deterioration of the spatial information content due the extensive pre-processing requirements of the radar image. Both optical and radar classifications allow to assess wetland characteristics that potentially influence plant and animal metacommunity structure. Envisat imagery, however, was less suitable than Landsat imagery for the extraction of detailed ecological information, as only large wetlands can be detected. This study has indicated that ecologically relevant data can be generated for the larger wetlands through relatively cheap imagery and standard techniques, despite the relatively low resolution of Landsat and Envisat imagery. For the characterisation of very small wetlands, high spatial resolution optical or radar images are needed. This study exemplifies the benefits of integrating remote sensing and ecology and hence stimulates interdisciplinary research of isolated wetlands.

Beaver ( Castor canadensis) mitigate the effects of climate on the area of open water in boreal wetlands in western Canada

Shallow open water wetlands provide critical habitat for numerous species, yet they have become increasingly vulnerable to drought and warming temperatures and are often reduced in size and depth or disappear during drought. We examined how temperature, precipitation and beaver ( Castor canadensis) activity influenced the area of open water in wetlands over a 54-year period in the mixed-wood boreal region of east-central Alberta, Canada. This entire glacial landscape with intermittently connected drainage patterns and shallow wetland lakes with few streams lost all beaver in the 19th century, with beaver returning to the study area in 1954. We assessed the area of open water in wetlands using 12 aerial photo mosaics from 1948 to 2002, which covered wet and dry periods, when beaver were absent on the landscape to a time when they had become well established. The number of active beaver lodges explained over 80% of the variability in the area of open water during that period. Temperature, precipitation and climatic variables were much less important than beaver in maintaining open water areas. In addition, during wet and dry years, the presence of beaver was associated with a 9-fold increase in open water area when compared to a period when beaver were absent from those same sites. Thus, beaver have a dramatic influence on the creation and maintenance of wetlands even during extreme drought. Given the important role of beaver in wetland preservation and in light of a drying climate in this region, their removal should be considered a wetland disturbance that should be avoided.

The Role of the Wetland Reserve Program in Conservation Efforts in the Mississippi River Alluvial Valley

The Mississippi River Alluvial Valley includes the floodplain of the Mississippi River from Cairo, Illinois, USA, to the Gulf of Mexico. Originally this region supported about 10 million ha of bottomland hardwood forests, but only about 2.8 million ha remain today. Furthermore, most of the remaining bottomland forest is highly fragmented with altered hydrologic processes. During the 1990s landscape-scale conservation planning efforts were initiated for migratory birds and the threatened Louisiana black bear (Ursus americanus luteolus). These plans call for large-scale reforestation and restoration efforts in the region, particularly on private lands. In 1990 the Food, Agriculture, Conservation and Trade Act authorized the Wetlands Reserve Program (WRP). The WRP is a voluntary program administered by the United States Department of Agriculture that provides eligible landowners with financial incentives to restore wetlands and retire marginal farmlands from agricultural production. As of 30 September 2005, over 275,700 ha have been enrolled in the program in the Mississippi River Alluvial Valley, with the greatest concentration in Louisiana, Arkansas, and Mississippi, USA. Hydrologic restoration is common on most sites, with open-water wetlands, such as moist-soil units and sloughs, constituting up to 30% of a given tract. Over 33,200 ha of open-water wetlands have been created, potentially providing over 115,000,000 duck-use days. Twenty-three of 87 forest-bird conservation areas have met or exceed core habitat goals for migratory songbirds and another 24 have met minimum area requirements. The WRP played an integral role in the fulfillment of these goals. Although some landscape goals have been attained, the young age of the program and forest stands, and the lack of monitoring, has limited evaluations of the program's impact on wildlife populations.

A semiparametric hedonic model for valuing wetlands

A semiparametric hedonic price function is estimated to examine the effects of proximity to wetlands on property values using extensive wetland inventory and housing market data from Portland-Oregon, USA. The semiparametric method used in this study allows for estimation of the hedonic price function with flexible functional form and is computationally easier than most non-parametric models. Four general categories of wetlands – open water, emergent vegetation, forested and scrub shrub wetlands – are differentiated. The results indicate that proximity to open water wetlands has a positive association with property values, while the other types of wetlands have either a negative or insignificant relationship.

The effect of phosphorus enrichment on the nutrient status of a northern Everglades slough

The response of wetlands to elevated nutrient loads typically has been examined in the context of using wetlands for nutrient removal. However, concern over the degradation of natural wetlands following anthropogenic disturbance continues to increase. Most research has focussed on the response of emergent wetlands, with an emphasis on the role of macrophytes. In this study, 21 1.8 m2 enclosures (mesocosms) were placed in a pristine open-water (slough) wetland and subjected to 7 inorganic phosphorus (P) loads; 0, 0.4, 0.8, 1.6, 3.2, 6.4, and 12.8 g/m2/y. This study demonstrated that while the rate of specific P accumulation was a function of the loading rate, the duration of loading is a critical factor in the ultimate P concentration in the biota and soil. Thus, time is an important consideration when determining response to enrichment. Phosphorus added to the slough was removed rapidly by the initially abundant metaphyton (unattached floating and suspended periphyton) and epipelon (benthic periphyton), which concentrated P 10- to 50-fold above background periphyton concentrations. Metaphyton concentrated P more rapidly than epipelon; however, both assemblages stabilized P concentrations between 2.6–3.0 g/kg. Water lily responded to elevated P loads with increased leaf size and nutrient accumulation. After 2-y, water lily P concentrations in the highest loaded mesocosms were similar to those observed in periphyton. Soil and porewater nutrients were slower to respond to P enrichment. Soil P concentrations were unchanged by P enrichment except for the highest loaded mesocosms. After 1-y of P loading, mesocosms receiving 12.8 g/m2/y had soil P concentrations almost 2-fold higher than background concentrations. Porewater P concentrations also showed little change throughout the experiment, with the exception of load 12.8 g/m2/y, which increased dramatically after the 1st year. During the 2nd year, average porewater P concentrations in this highest load were over 50-fold higher than background concentrations. Nitrogen concentrations in periphyton and water lily also generally increased in response to increased P loads. The high affinity of periphyton and water lily for P, combined with their subsequent influence on N uptake, suggests that these components can play an important role in wetland nutrient cycling. The disappearance of these communities may result in a reduction in the nutrient assimilative capacity of wetlands.