Previous research on habitat associations of pond-breeding amphibians has used community assemblages as response variables because the intensive labor required to quantify population size is usually prohibitive. However, wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum) oviposit egg masses that can be surveyed rapidly; thus, we were able to quantify the influence of within-pond parameters on their annual breeding effort. During 2000–2001, we assessed the effects of hydroperiod, within-pond vegetation, canopy closure, hydrologic isolation, fish occurrence, and pond size on egg mass counts of wood frogs and spotted salamanders at 124 ponds in western Rhode Island. Study sites were stratified by road density, which served as an indirect measure of non-breeding habitat quality and quantity. Hydroperiod had a significant influence on annual breeding effort. Egg masses of both species were most abundant in seasonal ponds that dried between 1 August and 30 November. Breeding populations of spotted salamanders were smaller in ponds that dried before the end of July, whereas breeding populations of wood frogs were reduced in ponds that did not dry during our two-year study. Both species usually attached egg masses to shrubs or branches in shallow water near the water surface, which may explain why both species oviposited more egg masses in ponds with substantial vegetation complexity, including extensive coverage by shrubs and persistent non-woody vegetation. Although wood frogs were more likely than spotted salamanders to avoid ovipositing in ponds with fish, egg mass counts of both species were substantially reduced in ponds containing fish. Numbers of egg masses for spotted salamanders and wood frogs were similar between larger ponds and those as small as 0.05 ha and 0.15 ha, respectively. Previously, researchers proposed protecting isolated wetlands > 0.2 ha to sustain populations of pond-breeding amphibians, but our research suggests that wetlands as small as 0.05 ha may provide critical breeding habitat for some species in southern New England.

The relationship between environmental factors and the spatial distribution of maintained and actively used burrows of the grapsid crab Helograpsus haswellianus was studied at three saltmarsh sites in southeast Queensland, Australia. The sites had been modified by runnelling for mosquito-control, a method that transports low-amplitude tides to areas of saltmarsh. The study investigated the relationship between burrow density, burrow aperture size, and runnelling, as well as the effect of flooding or non-flooding tides and distance from a tidal source. Responses differed at the three sites. The most consistent pattern across all sites was that active burrows were most numerous between 30 and 50 m from the saltmarsh / mangrove interface at the landward side of the tidal source. At particular sites, there were significant relationships between burrow aperture size, tidal period, and the presence of runnels. Generally, few small burrows occurred low on the shore, while larger burrows were distributed across the shore to 50 m. At naturally dry sites, more burrows occurred within 5 m of the runnel, whereas at naturally wet sites, fewer burrows were found close to the runnel. As runnels transport low-amplitude tides, moisture conditions required for burrowing may very between flooding and non-flooding tides. Overall, the influence of tides on the density of crab burrows and their aperture sizes was of more importance than the presence of runnels alone.

Reference wetlands play an important role in efforts to protect wetlands and assess wetland condition. Because wetland vegetation integrates the influence of many ecological factors, a useful reference system would identify natural vegetation types and include models relating vegetation to important regional geomorphic, hydrologic, and geochemical properties. Across the U.S. Atlantic Coastal Plain, depression wetlands are a major hydrogeomorphic class with diverse characteristics. For 57 functional depression wetlands in the Upper Coastal Plain of South Carolina, we characterized the principal vegetation types and used a landscape framework to assess how local (wetland-level) factors and regional landscape settings potentially influence vegetation composition and dynamics. Wetland sites were stratified across three Upper Coastal Plain landscape settings that differ in soils, surface geology, topography, and land use. We sampled plant composition, measured relevant local variables, and analyzed historical transitions in vegetative cover types. Cluster analysis identified six vegetation types, ranging from open-water ponds and emergent marshes to closed forests. Significant vegetation-environment relationships suggested environmental “templates” for plant community development. Of all local factors examined, wetland hydrologic regime was most strongly correlated with vegetation type, but depression size, soil textural type, and disturbance history were also significant. Because hydrogeologic settings influence wetland features, local factors important to vegetation were partly predictable from landscape setting, and thus wetland types were distributed non-randomly across landscape settings. Analysis of long-term vegetation change indicated relative stability in some wetlands and succession in others. We developed a landscape-contingent model for vegetation dynamics, with hydroperiod and fire as major driving variables. The wetland classification, environmental templates, and dynamics model provide a reference framework to guide conservation priorities and suggest possible outcomes of restoration or management.

It is well documented that Louisiana is experiencing wetland loss at rates greater than any other locale in the world. High rates of relative sea-level rise, a combination of eustatic sea-level rise and subsidence, is anticipated to compound this problem further in the future through increased flooding and encroachment of saline water into freshwater wetlands. The research presented in this paper examines the interactive effect of increased salinity level, flooding depth, and soil type on the growth responses of a dominant Louisiana fresh-water marsh plant, Panicum hemitomon, whose prevalence in Louisiana is currently in decline. This study was conducted under greenhouse conditions and employed a factorial design consisting of three salinity levels (0, 1.5, 3.0 ppt), three hydrologic regimes (0, 10, 20 cm), and two soil types (high organic content, low organic content). Panicum hemitomon productivity was significantly reduced even under the relatively small increases in salinity level (1.5 and 3.0 ppt) imposed in this study. Interestingly, moderate flooding tended to increase productivity, although this relationship was not statistically significant. Significantly greater productivity was observed for plants grown in mineral soil compared with organic soil. These results indicate that any degree of saline influx into P. hemitomon-dominated wetlands will result in decreased vigor and localized decline of this species. Moderate increases in the degree of freshwater inundation may not be as damaging as originally expected and, in fact, may actually stimulate production. However, if increased flooding is accompanied by increased salinity levels, which is anticipated to occur, then the overall effect on this species will be detrimental.

There are very few published reports of soil respiration rates from tropical peatlands, despite their importance to global carbon cycling. This study quantified in situ soil respiration rates in a suite of tropical peatlands in Micronesia and Hawaii using a soil CO₂ flux chamber connected to a LI-COR 6400 Portable Photosynthesis Infrared Gas Analyzer. Soil respiration rates were higher in the warmer Micronesian peatlands (2.15–2.54 umol m⁻² s⁻¹) than in the cooler Hawaiian montane peatlands (0.83–1.81 umol m⁻² s⁻¹). The lone exception was the taro-cultivated peatland in Micronesia that had low soil respiration rates likely due to low amount of litterfall, root biomass, and root production. Deep standing water decreased soil respiration rates, while lowered water levels had mixed effects on soil respiration rates. Surprisingly, measured soil respiration rates were lower than rates measured in temperate and boreal peatlands in the summer. However, soil respiration rates in tropical peatlands are not limited by large diurnal or seasonal changes and can continue respiring at the same rates, resulting in higher annual CO₂ flux rates compared to other non-tropical peatlands.

Recovery of wetland function is the primary goal of wetland creation. This study was undertaken to quantify denitrification and soil characteristics of wetlands created after lignite mine reclamation in east Texas, USA. Surface-soil denitrification rate and capacity were quantified using an acetylene (C₂H₂) inhibition/gas chromatography method in created wetlands of two age classes (4–8 years, and 10 years) on two mine soil types. Soil texture, pH, total-N, ammonium (NH₄ ), nitrate (NO₃⁻), cation exchange capacity (CEC), total-P, and organic matter (OM) content were determined. Soil characteristics varied by soil type and by age. Denitrification rate ranged from less than 1 to 105 kg N ha⁻¹yr⁻¹, was highly variable, but did not differ among created wetlands. Denitrification rate was similar between natural and created wetlands. Denitrification capacity, denitrification rate when nitrate is in excess, ranged from 23 to 302 kg N ha⁻¹yr⁻¹ and varied by soil type. Denitrification appears to function as well in wetlands created on mine soil as in natural wetlands, but may be limited by soil characteristics.

This study determined lethal dose levels of road salt on selected macroinvertebrates from a Michigan, USA wetland under different testing conditions and related those levels to in situ chloride concentrations of standing water habitats along multi-lane highways. We conducted simultaneous acute (24 and 96 h) and chronic (15 d) toxicity experiments using laboratory containers, containers adjacent to a wetland, and in situ modular field PVC microcosms. Data showed that Callibaetis fluctuans, Physella integra, Hyallela azteca, and Chaoborus americanus had relatively high tolerance to elevated road-salt levels. Depending on test condition, road-salt 96 h LC₅₀ estimates ranged from greater than 5000 mg l⁻¹ (2558 mg l⁻¹ Cl⁻) to >10,000 mg l⁻¹ (4502 mg l⁻¹ Cl⁻) road salt for C. fluctuans and P. integra, respectively. For H. azteca and C. americanus, mortality was generally low at all salt concentrations, with road-salt 96 h LC₅₀ estimates >10,000 mg l⁻¹. Chloride concentrations of 43 impacted Michigan wetlands ranged from 18 to 2700 mg l⁻¹ Cl⁻¹, with 75% <334 mg l⁻¹, indicating that macroinvertebrate LC₅₀ chloride estimates for the study species are well above most concentrations of the 43 wetlands.

Wetland habitats continue to be lost at a unsettling rate, especially freshwater emergent wetlands that are isolated geographically. These are the predominant wetlands found in arid and semi-arid environments, where they serve as foci of regional biodiversity. This is especially true of the playa wetlands of the Southern High Plains of Texas, USA. The factors that determine and maintain biotic diversity in these wetlands are understood poorly. Consequently, this study examined the effect of island biogeographic and landscape features on the diversity of aquatic macroinvertebrates in playa wetlands. Macroinvertebrates were collected from playas three times during the spring and summer of 1994 and categorized as resident or transient taxa based on life history strategies. Diversity was estimated using taxonomic richness (richness) and Fisher's log-series alpha (α). Surrounding land-use practices influenced resident richness, whereas playa surface area affected resident and transient richness, as well as resident α. However, relationships differed among sampling dates. Regression analyses suggested that transient richness and α were influenced more by insular characteristics than by landscape features. The converse was true for resident richness and α. Therefore, both insular and landscape characteristics affected the diversity of macroinvertebrates in playa wetlands, but impacts were dependent on life-history strategy and time since inundation (i.e., sampling date). Consequently, conservation and management efforts targeting macroinvertebrates in playa wetlands will need to focus on the wetlands and characteristics of adjacent watershed features.

This study presents measurements and modeled estimates of fall water requirements for the seasonal wetlands under moist soil management at Lower Klamath National Wildlife Refuge in northern California, USA. For three representative seasonal wetlands on the refuge, we measured the total volume of water required to fill the units and partitioned this volume into three components: surface water volume, ET losses, and soil-saturation requirements. Flood-up of seasonal wetlands required an average inflow rate of 0.87 ha-m/ha, with a range from 0.55 to 1.08 ha-m/ha. Over half of this water goes to saturate the underlying soils. We present a model for determining the approximate fall water requirement of any seasonal wetland on the refuge, given information on the effective porosity, depth to groundwater, average precipitation and ET, and the volumetric capacity of the wetland. Using a combination of measurements and modeled or assumed rates, we estimated the total fall water requirements for the refuge for 1999, 2000, and 2001. The estimates compared favorably with measured fall water deliveries to the refuge for the three years. Lastly, we compared annual water requirements for seasonally flooded and permanently flooded wetlands at Lower Klamath National Wildlife Refuge. Water requirements for the two wetland habitat types are approximately equal, although there are differences in the timing of demand and the consumptive use. Permanently flooded wetlands require water throughout the season to satisfy evapotranspiration needs, and none of this water is returned to the system. Seasonally flooded wetlands require water only in the fall during flood-up, and much of this water is returned to the system in the spring.

Woodland vernal pools occur commonly throughout northeastern North America. These pools provide preferred breeding habitat for mole salamanders (Ambystoma spp.) and wood frogs (Rana sylvatica) and support an abundant and diverse macroinvertebrate fauna. Vernal pool hydrology, and especially hydroperiod or duration of the wet phase, affects the composition and productivity of pool fauna. The hydrology of ephemeral wetlands is dominated by local weather conditions. In this paper, I report a ten-year record of the relationships between precipitation and evapotranspiration and water-level change and hydroperiod in four typical southern New England vernal pools. Long-term average precipitation is evenly distributed throughout the year in the Northeast; potential evapotranspiration peaks in the summer months and exceeds precipitation from mid-June through mid-September. This period of water deficit causes the period of maximum vernal pool drying. Vernal pool hydroperiods were shorter and pools dried earlier in those years with larger cumulative water deficits, especially when early spring ground-water resources were below long-term means and late winter snowpack was reduced or absent. Weekly water-level change in vernal pools was significantly related to precipitation and potential evapotranspiration, with precipitation having 2–5 times greater effect than evapotranspiration. Under climate-change predictions of more episodic precipitation and increased evapotranspiration, vernal pools would dry earlier in the year and remain dry longer. These changes would adversely affect the successful reproduction of pool-breeding amphibians and isolate the remaining productive pools.

Alligators create disturbance patches within the Everglades, but little is known about spatial and temporal variation in alligator holes throughout this ecosystem. Forty-eight alligator holes in Water Conservation Area 3 of the central Everglades were sampled to assess variation in morphology and vegetation and to identify landscape- and habitat-level features that correlate to alligator-hole variation. Field observations and plant community ordination suggested three distinct categories of alligator holes: holes containing shrub/tree species (shrub holes), holes surrounded by marsh (marsh holes), and holes dominated by cattails (cattail holes). Shrub holes were the most species-rich and diverse of the three types. All alligator holes except for cattail holes contained a greater richness of vascular plants than the surrounding marsh. Cattail holes were deeper than shrub or marsh holes, and all holes were deeper than surrounding marsh. Major landscape features that may influence structure of alligator holes seem to be distance from canals and surrounding marsh vegetation matrix. Alligator holes increase spatial heterogeneity, influence plant community composition and structure, and increase biological diversity. Restoration and management plans for the Everglades ecosystem should ensure that this landscape feature is perpetuated.

Many small estuaries and coastal lagoons in different parts of the world may be classified as temporarily closed/open ecosystems. They are blocked off from the sea for varying lengths of time by a sand bar, which forms at the estuarine mouth. The lengths of the closed and open phases, which are determined primarily by the interaction of river inflow and the sea in the mouth region, affect the structure and functioning of the estuarine biotic community. Freshwater inflow to such estuaries is normally not measured, and observations on the duration of estuarine mouth openings/closures are very scarce. As a result, relevant management decisions are often made on the basis of general experience and intuitive judgment. This paper describes an innovative approach for linking hydrologic data to mouth state in ungauged estuaries. A key characteristic in the method is the stream/river flow duration curve. It is first established for a daily index, which reflects the upstream catchment wetness and is calculated using rainfall information from the nearest rain gauge(s). This duration curve is then used to convert the current precipitation index time series into a continuous daily inflow time series at the ungauged estuarine mouth location. The conversion is based on the assumption that precipitation index values in a small catchment, and daily inflows to the estuarine mouth correspond to similar probabilities on their respective duration curves. The paper further illustrates how the generated inflow data could be used for the simulation of a continuous time series of estuary mouth openings/closures. Inflows are routed through a reservoir model, and the estuary mouth is considered open on days when the spillage from an estuarine “reservoir” occurs. The approach is illustrated using limited observed data on estuary mouth conditions from the South African coastline.

A chronosequence of restiad peat bogs (dominated by Restionaceae) in the lowland warm temperate zone of the Waikato region, North Island, New Zealand, was sampled to identify the major environmental determinants of vegetation pattern and dynamics. Agglomerative hierarchical classification of vegetation data from 69 plots in nine different-aged bogs, initiated from c. 600 to c. 15,000 cal yr BP, identified eight groups. Six of these groups formed a sequence from sedges through Empodisma minus, the main peat-forming restiad species, to phases dominated by a second restiad species, Sporadanthus ferrugineus. The sequence reflected bog age and paralleled patterns of temporal succession over the last 15,000 years (from early successional sedges through mid-successional Empodisma to late successional Sporadanthus) derived from previous studies of plant macrofossils and microfossils in peat cores. This indicated that different-aged bogs in the Waikato region could be used to interpret temporal succession. The remaining two classificatory groups comprised plots from sites modified by drainage, fire, or weed invasion and currently dominated by non-restiad species. The relationships between environmental variables and the six groups representing restiad bog succession indicated that, as succession proceeds, von Post decomposition index and nutrients in the top 7.5 cm peat zone decrease. The most useful indicators of successional stage were von Post, total P, total N, and % ash. Environmental response curves of the dominant plant species separated the species along nutrient and peat decompositional gradients, with early successional species having wider potential environmental ranges than late successional species. Empodisma minus, a mid-successional species, also had a relatively wide environmental range, which probably contributes to its key role in restiad bog development.

The germination ecology, including primary and secondary dormancy, mortality of seeds, and seed-bank type, of 20 fen grassland species from Northern Germany was investigated using a combination of burial and germination experiments. To analyze primary dormancy and effects of after-ripening (dry storage for 28 days) on freshly matured seeds, germination was measured at two fluctuating temperature regimes (15/25°C and 5/15°C) in the light and in darkness. Temporal changes in dormancy were investigated by burying seeds at 8–10 cm depth in nylon bags, exhuming samples at bimonthly intervals over a period of two years, and analyzing germination at the above-mentioned temperature and light treatments. Additional seed samples were retrieved five years after burial to determine seed longevity and seed-bank type. Freshly matured seeds of all species except Bromus racemosus showed primary dormancy. Dry after-ripening significantly increased germination in Parnassia palustris and Triglochin palustre. Mortality of buried seeds of Bromus racemosus, Sanguisorba officinalis, and Succisa pratensis reached 100% within 12 months (transient seed banks). All other species germinated both in the first and in the second growth period after burial and (with the exception of Briza media) showed annual changes in dormancy. For Silene flos-cuculi and Juncus filiformis, dormancy cycles were detected only in the dark treatments. Most species had a lower percentage germination in darkness than in the light, and the greatest suppression of germination in darkness was found in the small-seeded species (Juncus filiformis and Parnassia palustris). The retrieval of seed samples after five years revealed that most of the fen grassland species examined have short-term, persistent seed banks and thus are buffered against years of poor seed production and/or seedling survival. In addition, a large proportion of the species maintain long-term, persistent seed banks from which re-establishment is possible if management practices and site conditions of degenerated fen grasslands become appropriate following restoration measures.

The relation between the occurrence of riverine wetlands in floodplains along a humid to semi-arid climatic continuum was studied in two regions. The first included 36 mid-reach streams from Colorado to Iowa, USA, a region with a broad range of PET ratios (potential evapotranspiration/precipitation) from 0.70 to 1.75. The second region included 16 headwater streams in eastern North Carolina with PET ratios ranging from 0.67 to 0.83. Wetland boundaries were identified in the field along transects perpendicular to the floodplain. The width of jurisdictional wetlands was compared with flood-prone width (FPW) and expressed as a percent. An increase in PET ratio corresponded to an exponential decrease in the percentage of the FPW that is wetland. Soil texture, duration of overbank flow, and stream order did not correlate with percentage of FPW that was wetland. Streams with a PET ratio greater than 0.98 did not have wetlands associated with them. Greater channel cross-sectional areas correlated positively with greater wetland widths in both study regions. Overbank flow did not appear to contribute to wetland prevalence. Supplemental ground-water sources, however, as indicated by greater base flows, could not be ruled out as sources contributing to wetland occurrence.

In northern peatlands with water tables at or near the surface, the Sphagnum moss layer is potentially the only aerobic region where CH₄ oxidation can occur. We hypothesized that mosses with varying physiologies would create different conditions for methane-oxidizing bacteria and, in turn, affect rates of CH₄ consumption. We measured in-vitro CH₄ consumption potential of Sphagnum magellanicum and Sphagnum capillifoliun taken from the same habitat and S. magellanicum and Sphagnum majus across habitats to compare and contrast species and environmental effects. In certain cases, S. capillifolium consumed CH₄ more rapidly than S. magellanicum taken from identical habitats, although the greatest difference in consumption rates between species was only 29 μg CH₄ g⁻¹ dry moss d⁻¹, compared to a maximum difference of 126 and 415 μg CH₄ g⁻¹ dry moss d⁻¹ in S. magellanicum and S. majus sampled from different habitats. In most cases, CH₄ was consumed most rapidly in the lower, non-photosynthetic portions of the Sphagnum mosses, and consumption potential increased with an increase in the concentration of CH₄ in the habitat. We hypothesize that CH₄ consumption occurred internally, likely in the hyaline cells, as external surface sterilization did not significantly alter CH₄ consumption rates. This work provides evidence that different Sphagnum moss species have variable ability to oxidize CH₄, although inter-species differences are small compared to differences across habitats.

Nutrient limitation is often assumed to be similar among the species of a plant community. However, limitation can differ among ecosystems and among life forms and individual species within a particular ecosystem. Peatlands have some of the lowest nutrient availabilities and highest acidities among wetland types, but the relative roles of nutrient limitation and pH stress in structuring peatland plant communities are unknown. Accordingly, we measured changes in above-ground net primary production (ANPP) and percent cover of plants to additions of low levels of N, P, and calcium carbonate in a bog and fen in northern Minnesota, USA. Plots were treated for three years with a combination of 2 or 6 g N m⁻² yr⁻¹ as ammonium, 0.67 or 2 g P m⁻² yr⁻¹, and/or calcium carbonate to raise the pH of the bog from 3.8 to 4.9 and the pH of the fen from 4.9 to 6.4. In the bog, the low N treatment increased ANPP, whereas the high N treatment inhibited ANPP. Lime addition also stimulated ANPP. The whole-community bog response was largely due to bryophytes, which accounted for 76% of ANPP on average. However, the productivity of the shrub community (18% of total ANPP) increased with P additions but only during the third year of fertilizer application. Productivity of the bog graminoids did not respond significantly to any addition. Fen ANPP was stimulated by P addition, but the effect was isolated to graminoids (95% of total ANPP), and this was largely due to the response of Carex exilis. Our results suggest that low nutrient availability does not necessarily imply nutrient limitation of peatland plant communities. Furthermore, life forms and individual species responded differently, indicating that there are several levels of nutrient limitation within each peatland community. In particular, bog Sphagnum mosses appear to have a very low tolerance for N. Production and community structure were controlled by N-availability and pH in the bog and by P-availability in the fen.

Two sets of small scale systems of staged, vertical-flow constructed wetlands (VFCW) were operated in a greenhouse to study the purification of dibutyl phthalate (DBP) in admeasured water. Each system consisted of two chambers in which water flowed downward in chamber 1 and then upward in chamber 2. The systems were intermittently fed with wastewater under a hydraulic load of 420 mm·d⁻¹. The measured influent concentrations of DBP in the experimental system were 9.84 mg·l⁻¹, while the other system was used as a control and received no DBP. Effluent concentrations of the treated system averaged 5.82 μg·l⁻¹ and were far below the Chinese DBP discharge standard of ≤0.2 mg·l⁻¹. These results indicate the potential purification capacity of this new kind of constructed wetland in removing DBP from a polluted water body.

Peatlands often show patterns of small-scale topographic self-organization, such as hummock and hollow assemblages. When attempting to characterize peatland pore-water quality, little attention is typically paid to the micro-site characteristics of the sampling location, or only one microtopographical form is sampled for consistency. However, no information exists regarding whether or not these microtopographic landforms exert a direct influence over, or are influenced by, the chemistry of peat pore waters beneath them. As part of a larger study examining the role of peatlands in catchment-scale methylmercury cycling, the pore waters beneath several peatland microtopographical landforms were sampled for methylmercury. Pore-water methylmercury (MeHg) concentrations at the water table followed the trend: Shallow Hollow > Lawn > Hummock > Deep Hollow, with the shallow hollows having pore-water methylmercury concentrations over 3.5 times higher than that found in deep hollows. There was no significant difference in MeHg concentrations in pore waters from −25 cm. More detailed profiles of MeHg, sulfate and DOC concentrations, and pH in a poor fen shallow and deep hollow and a raised bog hollow show strong differences in pore-water solute chemistry, suggesting a complex interplay among hydrology, biogeochemistry, and microtopography. Evidence of wide variation in pore-water quality between sites and over time has significant implications for the sampling approaches used to characterize peatland pore-water chemistry.

The benthic invertebrates of three adjacent wetlands in northeastern Ohio, USA were sampled with a benthic corer during May–August 2001. The three wetlands consisted of a deep created wetland that overflowed into a shallow created wetland and a pre-existing natural wetland. The created wetlands were four years old and seeded with cattails. Forty-two invertebrate taxa were collected from all wetlands combined, and 11 taxa were abundant (represented >1% of total). Taxa richness, evenness, and community similarity were comparable among the three wetlands. Seed shrimp (Ostracoda), midges (Diptera: Chironomidae), copepods (Copepoda), fingernail clams (Bivalvia: Sphaeriidae), and water fleas (Cladocera) were the five most abundant taxa (38%, 13%, 11%, 9%, and 8%, respectively). Clams were significantly more abundant in the natural wetland, whereas no significant difference in density of other invertebrates was detected among wetlands. Laboratory inundations of soil taken from the rapidly drying basins of the natural and shallow created wetlands produced 10 taxa that survived the dry periods with desiccation-resistant stages and were dominated by microcrustaceans, Aedes mosquitoes (Diptera: Culicidae), clams, and annelid worms. Our data indicate that the created wetlands developed benthic invertebrate communities that were similar to the adjacent natural wetlands in a short period of time (four years), but clams were slow to colonize the human-made habitats.

Water-level monitoring was initiated on several wetland complexes on the Canadian Prairies in the early 1960s. Many of these wetland complexes are still actively being monitored using a method that obtains point measurements of water depth that can be used to determine water-level changes over time. This paper describes the depth-gauging method used in obtaining long-term water-level data for wetlands on the Canadian Prairies. This method has proven to be very reliable provided that observers are diligent about following procedural guidelines. Point measurements of relative depth resulted in stage values within 25 mm of those measured using conventional level surveys. In wetlands where more than one monitoring marker is deployed to monitor the range of water levels, a conversion factor is often used to determine maximum depth. The accuracy in determining maximum depth with a conversion factor is considered to be within 50 mm. Experience has demonstrated that the reliability of this method is dependent on the consistency of data collection, vigilance in the field, and careful screening of the data. Maintaining horizontal position of the measurement location is important, as the lowest point in the wetland is used as a relative datum. Vertical movements of the monitoring marker can also result in errors in the data if not identified and corrected accordingly.