Wetland management in the United States has never been as challenging as in today's highly modified landscape. Initially, wetland science and management emerged as professions in response to widespread conversion of wetlands to other uses and concerns over negative impacts on wildlife populations, especially migratory birds. Consequently, wetland management was focused on wildlife, and the initial management technique was simply to protect wetlands. However, extensive conversion of lands for agricultural and urban expansion over the past 60 years has modified ecosystem processes at the landscape scale sufficiently to compromise wetland management activities on adjacent lands dedicated to conservation. Moreover, society now expects a broad suite of ecosystem services to be delivered. As a result, many previously used wetland management techniques are no longer appropriate because they do not take into account influences of adjacent land uses or other ecosystem services, such as ground-water recharge. Other early management approaches may have been ineffective because they were based on an incomplete understanding of wetland processes or social influences. Meanwhile, wetland losses continued, as well as loss of services provided by the remaining managed wetlands. Regulation starting in the 1970s and subsequent research attention on wetland functioning has led to new knowledge and a broader understanding of wetland processes and recognition of the full suite of services (e.g., water storage, water quality improvement, aquifer maintenance, climate mitigation). To be effective in today's highly modified landscape, knowledge of social choices, political influences, and dynamic wetland processes is required to meet wetland management objectives for a range of ecosystem services. We argue that adopting a process-based perspective is critical to develop strategies to optimize a suite of wetland services, including providing traditional wildlife habitat.

The failure of managed wetlands to provide a broad suite of ecosystem services (e.g., carbon storage, wildlife habitat, ground-water recharge, storm-water retention) valuable to society is primarily the result of a lack of consideration of ecosystem processes that maintain productive wetland ecosystems or physical and social forces that restrict a manager's ability to apply actions that allow those processes to occur. Therefore, we outline a course of action that considers restoration of ecosystem processes in those systems where off-site land use or physical alterations restrict local management. Upon considering a wetland system, or examining a particular management regime, there are several factors that will allow successful restoration of wetland services. An initial step is examination of the political/social factors that have structured the current ecological condition and whether those realities can be addressed. Most successful restorations of wetland ecosystem services involve cooperation among multiple agencies, acquisition of funds from non-traditional sources, seeking of scientific advice on ecosystem processes, and cultivation of good working relationships among biologists, managers, and maintenance staff. Beyond that, in on-site wetland situations, management should examine the existing hydrogeomorphic situation and processes (e.g., climatic variation, tides, riverine flood-pulse events) responsible for maintenance of ecosystem services within a given temporal framework appropriate for that wetland's hydrologic pattern. We discuss these processes for five major wetland types (depressional, lacustrine, estuarine, riverine, and man-made impoundments) and then provide two case histories in which this approach was applied: Seney National Wildlife Refuge with a restored fen system and Bosque del Apache National Wildlife Refuge where riverine processes have been simulated to restore native habitat. With adequate partnerships and administrative and political support, managers faced with degraded and/or disconnected wetland processes will be able to restore ecosystem services for society in our highly altered landscape by considering wetlands in their given hydrogeomorphic setting and temporal stage.

Wetland science emerged as a distinct discipline in the 1980s. In response, courses addressing various aspects of wetland science and management were developed by universities, government agencies, and private firms. Professional certification of wetland scientists began in the mid-1990s to provide confirmation of the quality of education and experience of persons involved in regulatory, management, restoration/construction, and research involving wetland resources. The education requirements for certification and the need for persons with specific wetland training to fill an increasing number of wetland-related positions identified a critical need to develop curriculum guidelines for an undergraduate wetland science and management major for potential accreditation by the Society of Wetland Scientists. That proposed major contains options directed toward either wetland science or management. Both options include required basic courses to meet the general education requirements of many universities, required upper-level specialized courses that address critical aspects of physical and biological sciences applicable to wetlands, and a minimum of four additional upper-level specialized courses that can be used to tailor a degree to students' interests. The program would be administered by an independent review board that would develop guidelines and evaluate university applications for accreditation. Students that complete the required coursework will fulfill the education requirements for professional wetland scientist certification and possess qualifications that make them attractive candidates for graduate school or entry-level positions in wetland science or management. Universities that offer this degree program could gain an advantage in recruiting highly qualified students with an interest in natural resources. Alternative means of educating established wetland scientists are likewise important, especially to provide specialized knowledge and experience or updates related to new management discoveries, policies, and regulations.

The loss of small, seasonal wetlands is a major concern for a variety of state, local, and federal organizations in the northeastern U.S. Identifying and estimating the number of vernal pools within a given region is critical to developing long-term conservation and management strategies for these unique habitats and their faunal communities. We use three probabilistic sampling methods (simple random sampling, adaptive cluster sampling, and the dual frame method) to estimate the number of vernal pools on protected, forested lands. Overall, these methods yielded similar values of vernal pool abundance for each study area, and suggest that photographic interpretation alone may grossly underestimate the number of vernal pools in forested habitats. We compare the relative efficiency of each method and discuss ways of improving precision. Acknowledging that the objectives of a study or monitoring program ultimately determine which sampling designs are most appropriate, we recommend that some type of probabilistic sampling method be applied. We view the dual-frame method as an especially useful way of combining incomplete remote sensing methods, such as aerial photograph interpretation, with a probabilistic sample of the entire area of interest to provide more robust estimates of the number of vernal pools and a more representative sample of existing vernal pool habitats.

Depressional wetlands in agricultural landscapes are easily degraded by sediments and contaminants accumulated from their watersheds. Several best management practices can reduce transport of sediments into wetlands, including the establishment of vegetative buffers. We summarize the sources, transport dynamics, and effect of sediments, nutrients, and contaminants that threaten wetlands and the current knowledge of design and usefulness of grass buffers for protecting isolated wetlands. Buffer effectiveness is dependent on several factors, including vegetation structure, buffer width, attributes of the surrounding watershed (i.e., area, vegetative cover, slope and topography, soil type and structure, soil moisture, amount of herbicides and pesticides applied), and intensity and duration of rain events. To reduce dissolved contaminants from runoff, the water must infiltrate the soil where microbes or other processes can break down or sequester contaminants. But increasing infiltration also diminishes total water volume entering a wetland, which presents threats to wetland hydrology in semi-arid regions. Buffer effectiveness may be enhanced significantly by implementing other best management practices (e.g., conservation tillage, balancing input with nutrient requirements for livestock and crops, precision application of chemicals) in the surrounding watershed to diminish soil erosion and associated contaminant runoff. Buffers require regular maintenance to remove sediment build-up and replace damaged or over-mature vegetation. Further research is needed to establish guidelines for effective buffer width and structure, and such efforts should entail a coordinated, regional, multi-scale, multidisciplinary approach to evaluate buffer effectiveness and impacts. Direct measures in “real-world” systems and field validations of buffer-effectiveness models are crucial next steps in evaluating how grass buffers will impact the abiotic and biotic variables attributes that characterize small, isolated wetlands.

Bottomland hardwood (BLH) forests have important biogeochemical functions and it is well known that certain structural components, including pulsed hydrology, hydric soils, and hydrophytic vegetation, enhance these functions. It is unclear, however, how functions of restored BLH wetlands compare to mature, undisturbed wetlands. We measured a suite of structural and functional attributes in replicated natural BLH wetlands (NAT), restored BLH wetlands with hydrology re-established (RWH), and restored BLH wetlands without hydrology re-established (RWOH) in this study. Trees were replanted in all restored wetlands at least four years prior to the study and those wetlands with hydrology re-established had flashboard risers placed in drainage ditches to allow seasonal surface flooding. Vegetation, soils, and selected biogeochemical functions were characterized at each site. There was a marked difference in woody vegetation among the wetlands that was due primarily to site age. There was also a difference in herbaceous vegetation among the restored sites that may have been related to differences in age or hydrology. Water table fluctuations of the RWH wetlands were comparable to those of the NAT wetlands. Thus, placing flashboard risers in existing drainage ditches, along with proper management, can produce a hydroperiod that is similar to that of a relatively undisturbed BLH. Average length of saturation within the upper 15 cm of soils was 37, 104, and 97 days for RWOH, RWH, and NAT, respectively. Soil moisture, denitrification potential, and soluble organic carbon concentrations differed among wetland sites, but soil carbon and nitrogen concentrations, heterotrophic microbial activity, and readily mineralizable carbon concentrations did not. Significant linear relationships were also found between soil moisture and heterotrophic microbial activity, readily mineralizable carbon, and soluble organic carbon. In addition, sedimentation rates were higher in NAT and RWH wetlands than in RWOH sites. Results of this study suggest that reconnection of bottomland hardwood wetlands to their surrounding watershed through the restoration of surface hydrology is necessary to restore wetland functions important to nutrient and sediment removal.

In the Neotropics, differences in phytogeographic patterns and species richness respond non-randomly to edaphic factors in many upland forests. However, whether wetland forests follow the same species differentiation patterns is not well known. In this paper we analyze the relationship among species occurrences and selected soil characteristics, particularly salinity and acidity, in several wetland plant communities. Plant specimens were collected and soil samples analyzed for exchangeable cations, chloride, and organic carbon. Statistical methods were applied to assess β-diversity and to detect relationships between patterns of floristic variation and spatial variations of the soil conditions. β-diversity was high among vegetation communities. Edaphic conditions were heterogeneous, and landward gradients were present only for salinity and some exchangeable bases. This resulted in a lack of a straightforward relationship of vegetation patterns to salinity. More than 30% of the reported species covaried with at least one of the three acidity-related variables, suggesting that some tolerance to deleterious effects of H and Al³ at pH values < 4 is likely. Thus, in contrast to what we might expect in deltaic regions, acidity rather than salinity was the major factor driving species organization. However, variation of these soil characteristics taken together accounted for only 40% of floristic differences among communities.

Determining the success of restored wetland hydrology is often accomplished by documenting changes in wetland hydroperiod before and after restoration. Ideally, post-restoration hydropatterns would approach those that existed before site degradation. We evaluated the average monthly water-table levels of a mountain floodplain and fen wetland complex before and after restoration with manual wells that included seven or eight years of pre-restoration data and with electronic wells that included one or two years of pre-restoration data. Site restoration included reconstruction of a meandering 1.9 km stream channel to replace a previously straightened channel. A higher water table was noted within 50 m of the restored channel regardless of the length of pre-restoration assessment. Many of the manual wells further from the stream had insignificant changes in average monthly water levels, whereas higher water levels were common for the electronic wells regardless of proximity to the restored channel. The longer pre-restoration assessment period for the manual wells captured the climatic averages of rainfall and provided a more accurate description of pre-restoration conditions. The electronic wells provided the appropriate data to determine if a given area met the compliance aspects of wetland restoration, but a thorough assessment of hydrologic changes could not be accomplished with the electronic well data because of the lower annual rainfall during the shorter pre-restoration assessment. We recommend that pre- and post-restoration assessment periods account for rainfall variability when documenting changes in hydrology associated with wetland restoration in fluvial systems. If no control wetland or water-table data are available, periods of nearly-average rainfall are helpful for evaluating wetland hydroperiod before and after restoration.

In recent years, the Canadian federal government and several provincial governments have issued policies requiring compensatory mitigation (compensation) for unavoidable wetland loss. Canada's approach to compensation has been criticized for lacking guidelines, resulting in reduced transparency, unpredictability, and a lack of consistency. We solicited opinions and then synthesized regional expertise in Atlantic Canada through a Delphi process, established five guiding principles for compensation, and summarized opinion on compensation mechanisms. The five principles underscore the importance of 1) replacing wetland functions at a watershed scale, 2) predictability and transparency in the compensation process, 3) approaching compensation in a manner that is practical for responsible agencies and proponents, 4) assuring that proponents bear the full cost of compensation, and 5) iterative learning to improve compensation. Through the Delphi exercise, we found a preference for restoration, enhancement, and creation as compensation mechanisms, and limited support for mitigation banking. Our findings provide a solid foundation for the development of wetland compensation guidelines in Atlantic Canada and elsewhere.

The Agua Fria River in Arizona's Sonoran Desert was impounded and diverted more than 70 years ago. Immediately below New Waddell dam there are semi-permanent pools, but water has been released into the channel only during rare wet years. To determine whether a propagule bank exists below the dam, and whether it could contribute to the revegetation of the Agua Fria riparian ecosystem should flow be restored to the dewatered reach, we collected 45 soil cores from four plant associations. We examined species in the samples in a growth chamber using the seedling emergence method. A total of 74 species (mostly herbaceous) and an abundance of individuals were present in propagule banks. The propagule banks were similar to those of a free-flowing reference river despite considerable differences in extant vegetation. Riparian species were present in propagule banks of all four associations and were the dominant type in three (Tamarix forests, Tamarix-Salix forests, and Baccharis-Bebbia shrublands). Propagule distribution varied with soil depth in three of the associations (Tamarix forests and the two xerophytic shrublands) with riparian species more prevalent in deep sediment and upland species more prevalent in surface soil and litter. Collectively these patterns suggest that a riparian legacy is present in Agua Fria propagule banks. However, riparian propagule density was low in the Hymenoclea-Bebbia shrublands, reflecting xerification of the riparian corridor. Given the physical barrier of the dam, continued diversion of stream flow, and rare flood releases, local inputs from xerophytes will dominate propagule bank dynamics in the future. Although propagule banks could contribute to redevelopment of the herbaceous component of the vegetation should stream flows be restored to this river reach, the riparian legacy likely will decline over time as riparian propagules reach the end of their lifespan while propagules of xerophytes continue to be replenished.

Beavers (Castor canadensis Kuhl) can influence the competitive dynamics of plant species through selective foraging, collection of materials for dam creation, and alteration of hydrologic conditions. In the Grand Canyon National Park, the native Salix gooddingii C.R.Ball (Goodding's willow) and Salix exigua Nutt. (coyote willow) are a staple food of beavers. Because Salix competes with the invasive Tamarix ramosissima Ledeb., land mangers are concerned that beavers may cause an increase in Tamarix through selective foraging of Salix. A spatial analysis was conducted to assess whether the presence of beavers correlates with the relative abundance of Salix and Tamarix. These methods were designed to detect a system-wide effect of selective beaver foraging in this large study area (367 linear km of riparian habitat). Beavers, Salix, and Tamarix co-occurred at the broadest scales because they occupied similar riparian habitat, particularly geomorphic reaches of low and moderate resistivity. Once the affinity of Salix for particular reach types was accounted for, the presence of Salix was independent of beaver distribution. However, there was a weak positive association between beaver presence and Salix cover. Salix was limited to geomorphic settings with greater sinuosity and distinct terraces, while Tamarix occurred in sinuous and straighter sections of river channel (cliffs, channel margins) where it dominated the woody species composition. After accounting for covariates representing river geomorphology, the proportion of riparian surfaces covered by Tamarix was significantly greater for sites where beavers were present. This indicates that either Tamarix and beavers co-occur in similar habitats, beavers prefer habitats that have high Tamarix cover, or beavers contribute to Tamarix dominance through selective use of its native woody competitors. The hypothesis that beaver herbivory contributes to Tamarix dominance should be considered further through more mechanistic studies of beaver foraging processes and long-term plant community response.

Because Typha × glauca often dominates wetlands where humans have stabilized the natural hydrologic regime, we 1) compared its expansion rates where water levels were stabilized vs. fluctuating and 2) explored the potential for stabilized water levels to allow plants to accumulate more phosphorus (P) and increase growth. In three Wisconsin marshes, the area dominated by Typha expanded linearly over time, but rates were higher where water levels were stabilized than where they fluctuated naturally (based on nine aerial photos from 1963 to 2000). In a large wetland (412 ha) behind a dam, Typha × glauca expanded 81,152 m²/year, and clone diameters extended 3.9 ± 0.61 m/year. In contrast, a mixed stand (mostly T. angustifolia) in an upstream wetland with fluctuating water levels expanded only 2,327 m²/year, and clones extended only 2.5 ± 0.75 m/year. While various factors could have caused these differences, a separate two-factor experiment in outdoor microcosms supported the hypothesis that stabilized water levels alone can enhance T. × glauca spread. The experiment indicated that both stabilized water levels and P additions increased P accumulation and growth of T. × glauca. Constant inundation (5–10 cm deep) allowed T. × glauca to produce 56% more biomass (61.6 ± 4.0 g) than a regime with two drawdowns (39.4 ± 1.9 g; p < 0.001). Plants under constant inundation accumulated 0.15 ± 0.007 g P, which was 36% more than with one drawdown (0.12 ± 0.004 g; p < 0.001) and 67% more than with two drawdowns (0.09 ± 0.005 g; p < 0.001). Also as expected, the addition of 2 g P/m² increased biomass 23% more than the control (57.8 ± 3.0 vs. 46.9 ± 3.0 g/plant; p  =  0.02). Our microcosm results suggest that unavailable P can shift to a form that T. × glauca can use. Thus, internal eutrophication can augment rates of T. × glauca invasion.

Eutrophication from anthropogenic nutrient enrichment is a primary threat to the oligotrophic freshwater marshes of southern Florida. Macrophyte and periphyton response to increased phosphorus (P) has been well documented in both correlative and experimental studies, but the response of consumer communities remains poorly understood, especially in southern marl prairies. We conducted a P-loading experiment in in situ mesocosms in Taylor Slough, Everglades National Park, and examined the response of macroinvertebrate communities. Mesocosms at two sites were loaded weekly with P at four levels: control (0 g P/m²/yr), low (0.2 g P/m²/yr), intermediate (0.8 g P/m²/yr), and high (3.2 g P/m²/yr). After ∼2 yrs of P-loading, macroinvertebrates were sampled using periphyton mat and benthic floc cores. Densities of macroinvertebrate taxa (no./g AFDM) were two to 16 times higher in periphyton mats than benthic floc. Periphyton biomass decreased with enrichment at one site, and periphyton was absent from many intermediate and all high P treatments at both sites. Total macroinvertebrate density in periphyton mats increased with intermediate P loads, driven primarily by chironomids and nematodes. Conversely, total macroinvertebrate density in benthic floc decreased with enrichment, driven primarily by loss of chironomids and ceratopogonids (Dasyhelea). This study suggests that macroinvertebrate density increases with enrichment until periphyton mats are lost, after which it decreases, and mat infauna fail to move into benthic substrates in response to mat loss. These results were noted at nutrient levels too low to yield anoxia, and we believe that the decrease of macroinvertebrate density resulted from a loss of habitat. This work illustrates the importance of periphyton mats as habitat for macroinvertebrates in the Everglades. This study also indicates that in this system, macroinvertebrate sampling should be designed to target periphyton mats or conducted with special attention to inclusion of substrates relative to their coverage.

The Asian freshwater invasive bivalve, Limnoperna fortunei (Dunker 1857), was introduced into South America through the Rio de la Plata estuary (Argentina) at the beginning of the 1990s. Between 1995 and 1996, the bivalve was first observed in the middle reaches of Paraná River, 600 km upstream from its original point of entry to the system. Here, we describe the present zooplankton communities of two secondary channels of the Middle Paraná River floodplain (Colastiné and Santa Fe rivers) and contrast them with pre-invasion communities using zooplankton data obtained during 1974–1975 (Sante Fe River) and 1971–1973/1981–1982 (Colastiné River). In both floodplain rivers, total zooplankton and rotifer abundance during low water were significantly lower in the post-invasion period than they were pre-invasion. Prior to invasion, mean zooplankton abundance in low water was greater than in high water, while post-invasion mean zooplankton abundances during low and high water were similar. The rotifer Keratella was significantly more abundant prior to mollusc invasion. Zooplankton abundance and chlorophyll-a concentration declined compared to the pre-invasion period and were not correlated with post-invasion physical factors. Nutrient concentrations increased post-invasion from increased human development, but did not stimulated zooplankton or phytoplankton.

Biogeochemical transformations in wetlands impact water quality, nutrient transport across landscapes, and greenhouse gas exchanges with the atmosphere. This study examined anaerobic microbial respiration and methanogenesis in surficial sediments of six wetlands lying on glacial terrain in southwest Michigan, USA. Three of the wetlands were mainly groundwater-fed and three were mainly precipitation-fed. Ambient rates of denitrification, sulfate reduction, iron reduction, methanogenesis, and acetate turnover were measured at each wetland. Ambient denitrification rates were not detectable in any wetland, but denitrifying enzyme activity, measured in two wetlands, indicated that the potential to remove nitrate was higher in a groundwater-fed wetland. Iron reduction was measurable mainly in precipitation-fed wetlands while sulfate reduction was only measurable in the groundwater-fed wetlands. Methanogenesis was measurable in all wetlands, with no differences between wetlands with contrasting water sources, indicating that methanogenesis is important regardless of water source. Acetate turnover rates, which reflect total anaerobic respiration and methanogenesis, were higher in the groundwater-fed wetlands and proportional to the sum of the individual carbon mineralization rates across all wetlands. Even though there was substantial variation in the process rates among these wetlands, the general patterns indicate that water source influences the biogeochemical function of wetlands.

Constructed wetlands are cost effective wastewater treatment systems being increasingly used in agriculture. Efficient phosphorus (P) treatment by wetlands can however, be a challenge due to slow removal mechanisms. As a result, extended contact times are often required to achieve desired treatment. There are also concerns related to the long-term sustainability of P treatment. Therefore, a five year dataset from a surface flow constructed wetland located in Bible Hill Nova Scotia, Canada was examined to: 1) determine the effects of continued loading on P treatment and 2) evaluate hydrological impacts on P treatment. The wetland was intensively monitored year-round from November, 2000 through April, 2005 for total P (TP) and soluble reactive P (SRP). Dairy wastewater (milkhouse wash water and liquid manure) was loaded at 1.5 ± 1.0 kg ha⁻¹ d⁻¹ for TP and 1.0 ± 0.9 kg ha⁻¹ d⁻¹ for SRP. Mass reductions for the entire monitoring period were 53.7% and 52.7% for TP and SRP, respectively. Soils in this wetland appeared to have a sustained P adsorption capacity, with treatment being largely influenced by hydrology and fluctuations in wastewater loading rates. Linear regression of monthly TP and SRP mass reductions, with monthly outflow volumes resulted in decreased mass reductions with increased outflow. Monthly mass reductions were > 50% when corresponding outflows were < 100 mm. When monthly outflow exceeded 100 mm, however, mass reductions became highly variable. To maintain effective P management by constructed wetlands, the use of approaches that prevent high external hydrological loadings are recommended.

Nutrient dynamics in wetland ecosystems are largely controlled by soil moisture content. Therefore, the influence of soil moisture content on N mineralization should be explicitly taken into account in hydro-ecological models. The aim of this research was to establish relationships between N mineralization and soil moisture content in loamy to silty textured soils of floodplain wetlands in central Belgium. Large undisturbed soil cores were taken, incubated for 3 months under various moisture contents, and zero order and first order N mineralization rates were calculated. We used the percentage water-filled pore space (WFPS) as an expression of soil moisture because it is a better index for aeration dependent biological processes than volumetric moisture content or water retention. The relationship between the N mineralization rate and %WFPS was described by a Gaussian model. The optimum WFPS for N mineralization ranged between 57% and 78%, with a mean of 65% ± 6% WFPS. Expected annual net N mineralization rates at field temperature (9.7°C) and at optimal moisture content varied between 30 and 186 kg N ha⁻¹ (0–15 cm depth) year⁻¹, with a mean of 110 ± 42 kg N ha⁻¹ (0–15 cm) year⁻¹. The mean N turnover rate amounted to 2.3 ± 1.1 g N 100 g⁻¹ N year⁻¹. Multiple linear regressions between N mineralization and general soil parameters showed that soil structure has an overriding impact on N mineralization in wetland ecosystems.

We assessed short-term temporal and spatial variation of metal contents in the upper 100 cm sediment profile of intertidal marshes vegetated by common reed (Phragmites australis) along the Scheldt estuary in Belgium. The upper 0–100 cm sediment profile was sampled in three reedbeds at 56, 94, and 131 km from the river mouth. Sampling was repeated five times, at approximately two month intervals. Sediment properties such as texture and chloride, carbonate and organic matter content differed among locations. Metal accumulation, which is primarily due to association of metals with organic matter and clay in the surface sediment layer, seemed to be supplemented by an accumulation of sulphide precipitates deeper in the sediments. The depth at which sulphide precipitation significantly contributed to metal accumulation depended on the sampling location, and varied from less than 5 cm in clayey, organic sediments to more than 1 m in sandy sediments. Temporal variation of Cu, Cd, Pb, and Zn concentrations could only be linked to newly formed sulphides or sulphide oxidation at the sites with the lowest sulphide content. At sampling sites containing high sulphide amounts, variations should be primarily attributed to metal exchange and the presence of mobile metal complexes. Litter decomposition at the end of the growing season could hereby play a significant role.

Ground water beneath the seasonal swamp of the Okavango Delta, a recharge wetland in northwestern Botswana, is known to be a sink for solutes. In this study, measurements of organic carbon and inorganic ion concentrations, as well as UV-visible and fluorescence spectroscopy, were used to examine dissolved organic matter (DOM) storage and redox state of fulvic acids in ground water beneath an island and riparian woodland. Increasing dissolved organic carbon (DOC) concentrations along the ground-water flowpath suggests an accumulation of DOM in ground water, especially beneath island centers. However, the increase in DOC concentration was relatively less than the increase in chloride and sulfate concentrations, indicating non-conservative behavior of DOM in ground water beneath wetland islands. In combination with a decrease in fulvic acid content and specific UV absorbance, this result suggests that preferential sorption or destabilization of more aromatic organic compounds may be occurring under conditions of high pH and salinity. Finally, the increase in reduced fluorescence components (semiquinone- and hydroquinone-like components) along the ground-water flowpath strongly supports the transition to reduced fulvic acids in ground water of island centers. The reactivity and potential electron-shuttling function of fulvic acids may play an important role in the dissolution of metal oxides and associated DOM-iron-arsenic interactions in ground water of this recharge wetland.

We investigated how nutrient addition affects the abundance, nutrient storage, and competition between Distichlis spicata and Salicornia bigelovii, two dominant species in salt pans of Northern Gulf of Mexico marshes. Namely, we compared fertilized and unfertilized plots in monospecific areas colonized respectively by D. spicata or S. bigelovii, and in a mixed area colonized by the two species. Nutrient addition generally increased the aboveground biomass and percent cover of the two species, and those increases were moderate to large in relation to the increases found for other marsh plant species. Nutrient addition also generally decreased the carbon:nitrogen and carbon:phosphorus ratios of aboveground and belowground tissues of the two species. Our results provide evidence that, under enhanced nutrient availability, D. spicata is a superior competitor over S. bigelovii in the mixed zone of the salt pan where the two species grow together. However, we did not detect large changes in biomass dominance by D. spicata following fertilization, possibly because the experiment only lasted 10 months. Our results suggest that nutrient addition, by increasing the structural complexity of the leaf canopy and the nutritional quality of plant tissues for first-order consumers, may enhance the value of salt pans as habitat for organisms

In Central México, wetland plants are harvested for weaving, fodder, and fertilizer. To test whether harvesting alters plant diversity, we compared the effects of harvesting all vegetation once, follow-up harvesting of Typha domingensis Pers. one or three more times, and a non-harvested control, using two sites differing in water depth in an annually burned wetland near Morelia, México. After one year, harvesting treatments increased species richness at both the plot (14-m²) and wetland scales, increased the Shannon diversity index at the plot and subplot (1-m²) scales, and changed plant community composition (measured by Bray-Curtis distance) relative to control plots. Response among harvesting treatments was similar, and increased Typha harvesting did not have additive effects on Typha or on community composition. Grasses and short forbs (< 0.5-m tall) significantly increased in importance value in harvested plots, as did five individual forb species that were capable of vegetative spread. Uncommon species were significantly more likely to be found only in harvested plots than only in control plots, and new species (not initially present at the site) tended to recruit in harvested plots. Most new species were perennials that could likely tolerate additional harvesting. All harvesting treatments reduced Typha height, density, and rhizome starch reserves after five months, and responses were significantly affected by site, water depth, flowering ramet density, and pre-treatment values. Typha recovered in all harvested plots after one year, even when harvested four times, although flowering-ramet density declined in the wetter site. Community composition was more highly correlated with water depth and litter cover than with harvesting in an NMS ordination including both sites. Within sites, harvesting, light availability, leaf area index, and litter cover correlated similarly with variation in community composition. Given that our treatments reflect a subset of actual local management practices, harvesting could provide a sustainable and economically attractive management strategy for biodiversity conservation in this system, while the cessation of harvesting could lead to species loss.

Wetland managers rely on a variety of vegetation management techniques to set back plant succession, enhance seed production, create hemi-marsh conditions, and reduce the coverage of invasive plants in wetlands. We evaluated the effects of vegetation management techniques (prescribed burning, cattle grazing, mowing, and disking) on aquatic invertebrate communities in seasonal wetlands in the Rainwater Basin Region of Nebraska, USA. Because many of these wetlands are embedded in an agricultural landscape, we also evaluated the effects of agriculture on aquatic invertebrates. We conducted the study in 24 wetlands during spring 2004 and 2005. In general, aquatic invertebrate richness and diversity were similar among wetlands subjected to different management regimes. However, richness and diversity were highest in grazed wetlands and lowest in disked wetlands. Regardless of the management regime, total benthic and nektonic invertebrate biomasses were higher in managed wetlands than unmanaged wetlands. In 2004, naidid oligochaete biomass was highest in farmed wetlands. Cattle grazing, mowing, and prescribed burning seemed to have the greatest influence on individual taxa; 12, eight, and seven of the taxa (out of 32) had higher biomasses in grazed, mowed, and burned wetlands, respectively. Within mowed wetlands, the biomasses of some taxa (Gyraulus, Lymnaea, and Physa) were lower in managed areas than unmanaged areas, emphasizing the need to leave some areas unmanipulated to provide cover. Because of high spatial and temporal variability in wetlands and aquatic invertebrate communities, the response of aquatic invertebrates to vegetation management techniques was not consistent and no management regime offered a particular advantage in enhancing aquatic invertebrate communities. However, managers should be aware that some type of physical manipulation of aquatic vegetation in wetlands is still warranted on a regular basis to reduce nuisance vegetation, enhance seed production, and create optimal habitat conditions for migratory waterfowl and other wetland-dependent birds.

One critical component of any wetland restoration program is reliably documenting temporal changes in the spatial extent, pattern, and proportion of plant communities within the landscape. This study describes the development of a 2003 baseline vegetation map for a 42,635 ha wetland impoundment located in the northern portion of the remnant Everglades, Florida. Vegetation communities were photointerpreted and mapped with a ¼ ha minimum mapping grid unit from 1:24,000 scale color infrared aerial photography utilizing 1^st order analytical stereo-plotters. Results show an impoundment that has significantly changed in comparison to an earlier 1940s mapping effort. These included the loss of most of the tree island habitat and the establishment of large expanses of invasive cattail adjacent to and downstream of inflow structures with 28% of the grid cells containing cattail. Our techniques will be very useful in evaluating Everglade's restoration and are applicable to wetlands around the world.

Soluble reactive phosphorus (SRP) concentrations in wetland surface waters were measured during laboratory incubations in the presence of wetland soils and Typha leaf litter. Aerated water columns above intact soil cores increased in SRP concentration (up to 73 µg L⁻¹) over 28 days, whereas the water column in cores containing soil and a Typha litter layer showed no concentration increase (remained < 5 µg SRP L⁻¹). In the absence of soil, phosphorus (P) uptake by leaf litter and associated microbial biomass occurred rapidly under oxic conditions (max. 24-hr. uptake, 524 ± 90 µg P g⁻¹ dry litter d⁻¹), but uptake was slower and less complete under hypoxic conditions. At the highest tested initial P concentration of 1 mg L⁻¹, P uptake by litter under hypoxic conditions (< 0.5 mg O₂ L⁻¹) was 41% of the oxic rate, or 216 ± 42 µg P g⁻¹ dry litter d⁻¹. Differences between hypoxic and oxic P uptake rates, however, were not observed at initial SRP concentrations of 100 µg L⁻¹ or less. Our results suggest that leaf litter may be important to mitigating soil P release.

Geographic trends in surface water chemistry and leaf tissue nutrients may reflect gradients of nutrient limitation and broad-scale anthropogenic inputs. In 24 rain-fed (ombrotrophic) peatland bogs in Massachusetts and Vermont, we measured nutrient and metal concentrations in pore-water and in leaf tissues of three common bog plant genera – leather leaf (Chamaedaphne calyculata), northern pitcher plant (Sarracenia purpurea), and peat moss (Sphagnum spp.). The concentrations of N, P, and K were low in leaf tissues of all three plant genera, as were the concentrations of many trace heavy metals, including Cr, Cu, Co, Cd, Mo, and Pb. Stoichiometric ratios of macronutrients (N:P, P:K, and N:K) in plant leaves suggested that plant growth in the sampled bogs was limited by P, or was co-limited by all three macronutrients. N:P and N:K nutrient ratios of Sarracenia purpurea and Sphagnum spp. increased toward the northwest and with elevation, but stoichiometric ratios of Chamaedaphne calyculata did not show any clear geographic trends. A principal components analysis revealed additional distinct differences among the three plant genera in their nutrient and metal concentrations. Furthermore, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), Cu, Mg, NO₃, Al, and K in pore-water increased from the northwest (northwestern Vermont) to the southeast (Cape Cod and eastern Massachusetts near Boston), a gradient of increasing human population density and urbanization. In contrast, pore-water concentrations of SO₄ and Al were highest in the western sites, and SO₄ concentrations increased with elevations. These patterns may reflect atmospheric inputs from the Ohio River Valley leading to increased acidic deposition, causing Al to be leached from soils. Because bogs are naturally low in nutrients and do not receive substantial inputs from surrounding groundwater, the chemical signatures and nutrient stoichiometry of specific bog plant species or genera may provide useful indicators for assessing spatiotemporal changes in atmospheric deposition.

Over 6,110 ha of the commercial production salt ponds surrounding South San Francisco Bay, CA, have been decommissioned and reconnected to the bay, most as part of the largest wetlands restoration program in the western United States. These open water ponds are critical habitat for millions of birds annually and restoration program managers must determine the appropriate balance between retention of ponds versus re-conversion to tidal salt marsh, knowing that both are essential ecosystems for endangered bird species. Our study describes the ecological value of the new open water pond ecosystems as feeding habitats for birds. We used the oxygen rate of change method to determine ecosystem metabolic parameters from high resolution time-series of dissolved oxygen concentration. Areal gross primary production (8.17 g O₂ m⁻² d⁻¹) was roughly double the world's most productive estuaries. High rates of phytoplankton photosynthesis were balanced by equally high rates of community respiration (8.25 g O₂ m⁻² d⁻¹). Metabolic equilibrium was delicately poised: sharp irradiance and temperature shifts triggered short term photosynthesis reduction resulting in oxygen depletion. We converted net primary production (NPP) into potential carrying capacity of the forage biota that support targeted pond waterbirds. NPP was processed through both a pelagic food web, resulting in forage biota for piscivorous birds and a benthic food web, resulting in forage biota for shorebirds and diving benthivores. Both food webs included efficient algal-based and inefficient detrital trophic pathways. The result of all primary production being routed through simple food webs was high potential forage production and energy supply to waterbirds, equivalent to 11–163 million planktivorous fish or 19–78 billion small estuarine clams within the 330-ha pond between May and October. Food quantity does not necessarily equal quality and these systems have the potential to produce toxic or inedible algae. Our study provides the first measurement of primary production in the open water ponds of San Francisco Bay and presents a novel approach for transforming primary production into forage production as a metric of an ecosystem's energetic carrying capacity.

Sultan Marshes, an important ecosystem and wildlife refuge in the Develi Basin in Turkey, originally included two lakes and two freshwater marshes, with a total surface area of 176 km², surrounded by wet meadows and salt steppes. The Develi Irrigation Project changed the Sultan Marshes severely starting in 1988 by diverting surface and ground-water flows from the wetlands. Water diversions caused more than 1 m decline in water levels in the lakes and marshes. Spatial changes in the Sultan Marshes ecosystem with time were analyzed using Landsat images from 1980, 1987, 2000, and 2003 that were transformed into five information classes (water, marsh, agriculture, dry lake, and steppe) by unsupervised classification. Changes were identified by a post-classification change detection method. Classification accuracies were 89% to 93%, and accuracies of the change maps were 80% to 85%. The analysis showed that lake surface areas decreased by 93% from 1980 to 2003. Yay Lake was almost completely dry in 2003. The marshes receded more than 50%, and the surrounding steppe expanded into the lakes and marshes. Agriculture expanded in the western and eastern parts (Kepir Marshes) of the study area. Although the years 2000 and 2003 had lower than average annual precipitation, and lower annual precipitation than in 1980 and 1987, the changes in Sultan Marshes are so large that they cannot be solely attributed to weather fluctuations. Surface water diversions and increased use of spring waters and ground water are responsible for the changes.

We tested whether a trade-off exists between tolerance to flooding and tolerance to drought in wetland plants by assessing biomass accumulation, relative growth rate (RGR), survival rate, and physiological response of three wetland plants growing in drought or flooded environments. In wetlands of China's Sanjiang Plain, Carex lasiocarpa typically occurs at low elevations (10–50 cm water depths), Carex limosa at medial elevation (10–30 cm depths), and Deyeuxia angustifolia at high elevation (0–10 cm depths). Plants of three species were subjected to flooding and drought treatments (25 days) in a greenhouse experiment. In the flooding treatments, biomass accumulation (range 0.007–0.031 g per plant) and survival rate (11%) were lowest in D. angustifolia. Relative growth rate (RGR) was highest in C. lasiocarpa (−0.006 d⁻¹), intermediate in C. limosa (−0.051 d⁻¹), and lowest in D. angustifolia (−0.118 d⁻¹) at the end of the flooding experiment. Alcohol dehydrogenase (ADH) activity in C. lasiocarpa and C. limosa increased with flooding time, whereas ADH in D. angustifolia did not vary over the experimental period. These results indicated that tolerance to flooding from highest to lowest among the three species was: C. lasiocarpa > C. limosa > D. angustifolia. In the drought experiment, RGR was lower in C. lasiocarpa, but higher in C. limosa and D. angustifolia. At this experiment's end, only D. angustifolia plants still survived. Under drought conditions, production of malondialdehyde (MDA, an indicator for assessing a plant's ability to tolerate drought) showed the same pattern as ADH production under flooded conditions for all species. These results indicated that tolerance to drought from highest to lowest among the three species was: D. angustifolia > C. limosa > C. lasiocarpa. Our experiments indicate that a trade-off exists between tolerance to flooding and tolerance to drought in the three marsh plants.

Using data sets from two separate studies, we assessed within-year variation in aquatic invertebrate communities in 31 seasonally flooded (seasonal) wetlands in aspen (Populus spp.) – dominated forests in north central Minnesota. Principal components analysis (PCA) indicated that, in each case, three axes explained > 55% of variance in aquatic invertebrates, with the first axis strongly correlated with sampling date. Indicator species tests showed that this variation along axis 1 was largely due to shifts in abundance of crustaceans, Diptera and other insects, leeches, and other taxa. Temporal shifts in aquatic invertebrate community structure pose a major obstacle for ecological studies of aquatic invertebrates in seasonal forest wetlands and should receive more attention from investigators planning research in these and perhaps other wetland habitats.