Forested wetlands in metropolitan areas function to support biodiversity, protect water quality, store floodwaters, and maintain streamflow, but they also function to provide natural areas for passive recreation, education, and esthetic appreciation for the surrounding human populations. However, the presence of dense human populations in the watersheds of wetlands is usually associated with disturbance and the diminution of the capacity of the wetlands to provide socially-valued ecological functions. I have examined indicators of biological, hydrologic, biogeochemical, and social functions in a sample of twenty-one mature forested wetlands located in northeastern New Jersey, USA, part of the New York City metropolitan region, which supports over 2000 people km⁻². The field data and the principal components analyses of the sets of indicator variables for each class of function showed that the wetlands were arrayed along well-defined complex gradients in each case and that some functions were being performed at high levels in some of the wetlands despite the urban setting. However, the arrangement of sites within each ordination space differed, suggesting complex relationships among the various functions, some of which may be contradictory. For example, high ability to store floodwaters and evidence of flooding is associated with greater plant diversity and presence of obligate wetland species but is also associated with poor habitat for vertebrates and the presence of water-borne trash and exotic species. Conversely, low wetness is associated with high quality of habitat for vertebrates but also increased disturbance from large-scale dumping of trash and human disturbance and the release of nitrate from the soils. High levels of human use in and around the wetlands, while providing opportunity for human use and appreciation of the sites, is associated with low plant diversity and high release of nitrate-nitrogen. I conclude that because the functions performed by urban wetlands include human use and presence, there will necessarily be trade-offs required among ecological and human functions.

Long-term studies are essential to understanding the effects of urbanization on wetlands and the effectiveness of management actions. Using data from the National Wetlands Inventory (NWI) in combination with GIS analyses and field surveys, we tracked changes over 16 years (1982–1998) in small (≤2 ha), palustrine emergent/open water wetlands (PEM/POW) in Portland, Oregon, USA. Wetlands identified on NWI maps and that had not been converted to other land uses at the time of the 1992 survey were surveyed in 1998. Data were collected on 164 of the 171 wetlands in the target population. Despite development pressure throughout the 1990s, loss of small PEM/POW wetlands slowed between 1992 and 1998, with only 6% of the sites being destroyed as compared to 40% between 1982 and 1992. Of 11 sites that were not identifiable due to drought in 1992, eight had recovered with the return of typical rainfall; three had been destroyed. Most of the wetlands existing in 1998 were in hydrogeomorphic (HGM) classes atypical to the region due to human manipulation. Hydrologic modifications were observed on 60% of the sites, but on-site disturbances like mowing, dumping, and trail building had decreased since the 1992 survey. Over the time period studied, land uses adjacent to the study sites shifted from undeveloped and agricultural to urban and residential use. Reflecting the common occurrence of on- and off-site stressors and modifications, we rated the condition of only 11% of the sites as good, with 46% fair and 43% poor. Our results demonstrate the utility of combining field surveys with GIS analyses to track the status of wetland resources over time. The next challenge is to use such data to develop strategies to manage urban wetlands in ways that maintain and ultimately improve the condition of the resource.

Wetlands provide a range of valuable ecosystem services from water purification and nutrient retention to recreation and aesthetics. The value of these services is often difficult to quantify and document to policy makers and the general public. Economists have developed non-market approaches to address difficult issues related to valuation of the environment. This paper reviews recent literature on non-market valuation as applied to wetlands, with a particular focus on the value of urban wetlands. Wetland valuation studies have generated a wide range of values, in part due to differences in what is valued and in part due to differences in methodology. Several studies have shown that property owners value proximity to wetlands in urban areas. In addition, studies have found positive values for recreation (fishing and hunting), commercial fishing, water purification, and other ecosystem services provided by wetlands, although little of this work has been done on urban wetlands. Valuation studies can provide useful information about relative rankings of value, showing, for example, that certain types of wetlands or certain services are more highly valued than others. Whether the absolute magnitude of valuation estimates is correct is less clear.

In an interdisciplinary project to develop protocols for long-term cultural and ecological monitoring of wetland restorations in Minnesota, we compared restored and reference wetlands on several ecological and cultural measures including land-use context, cultural perceptions, and management practices. Cultural measures were drawn from our surveys of visitors, neighbors, planners, and managers of the wetlands. This paper discusses their perceptions of six metropolitan wetlands (four recent restorations and two reference sites), how cultural measures of their perceptions compared with selected site characteristics and biodiversity measures, and what results suggest for wetland design and management. Overall, sites that were perceived as more well-cared-for and as a good place to enjoy nature were perceived as more attractive. In addition, objective site characteristics, like cultural cues and natural landscape context, were related to perceived attractiveness. While plant species richness was not significantly related to perceived wetland attractiveness for our sites, bird species richness was related to attractiveness.

Alkaline wetland beaches provide crucial habitat for breeding piping plovers (Charadrius melodus) in the northern Great Plains of the United States and Canada. Vegetation encroachment has been identified as a potential threat that decreases alkaline beach habitat availability, but the long-term status of these breeding habitats has not been evaluated. We measured vegetation changes at two North Dakota alkaline wetland complexes from 1938 to 1997. Total beach habitat, including lower beaches that were impacted by flooding, varied substantially among years based on changes in surface-water levels. Quantities of upper-beach habitats, which were not affected by inundation, were negatively correlated with precipitation amounts during the previous five-year periods. We measured declines in upper-beach habitat averaging 0.89 ha/yr and 0.20ha/yr at our two wetland complexes from 1938 to 1997, suggesting that long-term changes in factors other than precipitation (e.g., ground-water hydrology, livestock grazing intensity, or fire frequency) may be negatively affecting beach availability. Vegetation reduction may be critical to long-term recovery of threatened piping plovers in the Great Plains.

Larvae of wetland caddisflies supplement their detrital diets with animal material. In some species this supplement is obtained by preying on other caddisflies. In this study, we conducted a series of laboratory experiments to a) compare intraspecific aggression and the propensity for cannibalism among six caddisfly species that occur along a gradient from vernal to autumnal to permanent high-elevation wetlands, and b) determine the importance of cases in preventing or reducing cannibalism and intraguild predation. We predicted that cannibalism and overall levels of aggression should be highest in species that occur in temporary habitats. We found that all of the species that use temporary habitats (Asynarchus nigriculus, Hesperophylax occidentalis, Limnephilus externus, Limnephilus picturatus, Limnephilus secludens) were extremely aggressive towards and cannibalized conspecifics without cases. Species that typically occur in short-duration temporary wetlands were more aggressive than those in long-duration temporary wetlands. Cases prevented cannibalism in four of these temporary-habitat species, and reduced cannibalism among Asynarchus larvae. The latter species occurs in extremely ephemeral habitats where cannibalism provides a dietary supplement that probably facilitates emergence before drying. Asynarchus also preys on Limnephilus spp., and we found that cases dramatically reduced vulnerability to intraguild predation. Larvae of Agrypnia deflata, a species that occurs only in permanent wetlands, were least aggressive and rarely cannibalized conspecifics. Our results are consistent with the hypothesis that intraspecific aggression and the potential for cannibalism are highest in species that live in habitats with developmental time constraints. Many wetland invertebrates face developmental time constraints and selection for aggression in temporary habitats should be especially strong for taxa that rely on animal material to supplement a mainly detrital diet.

Ectomycorrhizae are symbiotic relationships between soil fungi and higher plants. Evidence of the symbiosis is the presence of a ‘mantle,’ a hyphal layer that covers root tips, and a change in root morphology. The potential use of ectomycorrhizal mantles as hydrology indicators for wetland determinations was evaluated on the Delmarva Coastal Plain (Delaware and eastern shores of Maryland and Virginia, USA) over three seasons. In theory, the distribution of mantles with soil depth should vary from uplands to wetlands in most years, as mantle development is considered to be impeded by anaerobic conditions. At four forested locations, plots were set up in seasonally-saturated wetlands and adjacent uplands and drained wetlands (twelve sub-sites). Plots were evaluated according to the Corps of Engineers Wetlands Delineation Manual for soils, plant community, and hydrology to identify a jurisdictional classification. Hydrology was further addressed using automated monitoring wells (twice daily readings), and anaerobic conditions were confirmed via platinum electrodes. Plant roots (Pinus taeda was targeted) were sampled via spade slices in March and August each year and separated by depth: O horizon, 0–5 cm, 5– 10 cm, 10–15 cm, and 15–20 cm. Roots were evaluated for the presence of mantles. A threshold depth of 5 cm was identified. From a total of 892 roots with mantles in uplands (including effectively-drained wetland sub-sites), 253 (28%) were found below the threshold depth. For wetlands (including one ineffectively-drained wetland), seven of 331 roots with mantles (2%) were found below the threshold depth. Temporal and spatial variability in mantle data was common; however, mantles consistently occurred at greater depths where seasonally high water tables were lower. We concluded that mantle depth has potential as a hydrology indicator.

Porewater concentrations and benthic fluxes of dissolved inorganic carbon (DIC), sulfate (SO₄²⁻), calcium (Ca² ), manganese (Mn), iron (Fe), ammonia (NH₄ ), and soluble reactive phosphorus (DIP) were measured in the sediments of Albufera d'Es Grau (Minorca Island), a mesohaline lagoon, in Spring/early Summer. In this period, DIC and NH₄ were produced in sediments by the decomposition of organic matter through aerobic pathways in the upper 1 cm and below this depth through anaerobic pathways mainly sulfate reduction. In March, the average flux of DIC into the water was 21.45 ± 26.05 mmol m⁻² d⁻¹, more than 50% of which came from anaerobic respiration below 1 cm sediment depth. In June, the DIC flux increased to 55.29 ± 24.38 mmol m⁻² d⁻¹, but the rates of production through sulfate reduction decreased drastically to less than 10% of the total flux. NH₄ -flux was also relatively low, decreasing from 1000 μmol m⁻² d⁻¹ in March to 200 μmol m⁻² d⁻¹ in June. Differences between stoichiometric relationships in porewater and in measured fluxes indicated immobilization of nitrogen in sediments due to macrophyte uptake and nitrification, this immobilization mainly occurring in early summer. DIP release into the water was always below 15 μmol m⁻² d⁻¹, these low values being attributed to three main factors: a) more than 40% of sedimentary phosphorus in Es Grau sediments occurred in non-reactive forms such as detrital apatite or refractory-P; b) accumulation of Fe-oxides at the sediment surface acts as a trap for DIP produced through organic matter decomposition in March; and c) phosphate released from Fe-bound P in June during the period of increased oxygen consumption was effectively trapped as fulvic-P complexes and as microbial phosphate. Differences between fluxes directly measured and estimated from porewater concentrations also indicated that, at some sites, bioturbation contributed to the total flux of NH₄ and Mn and phosphate immobilization.

Wetland mulching is the transfer of surface soil (often from a wetland that will be filled or otherwise impacted) onto the surface of a wetland creation area to provide wetland vegetation, organic matter, and soil organisms. A total of 33 herbaceous wetland creation areas (17 mulched and 16 non-mulched) in the Tampa, Florida, USA region were studied at the end of the wet season (November) and subsequent dry season (June) to determine the effects of mulching. All wetland creation areas were constructed between 5 and 11 years prior to the study. Using the seasonally flooded zone of each wetland, we examined the effects that mulching has on 1) percent organic matter in the soil, 2) the Prevalence Index (measure of hydrophytic vegetation occurrence) of plant communities present, 3) species richness, evenness, and diversity (Shannon Index), 4) total vegetation cover, 5) above-ground biomass production, 6) soil pH, and 7) nutrient content. Mulched wetlands had a higher percent organic matter in the soil than non-mulched wetlands (5.9 ± 0.5% vs. 2.6 ± 0.3%, respectively). In November, the mulched wetlands had lower Prevalence Index values, species richness, and diversity values than non-mulched wetlands. Between November and June, non-mulched wetlands decreased in species richness (10.6 ± 0.7 to 6.6 ± 0.6 per m²) and overall diversity (Shannon Index values 1.74 ± 0.08 to 1.28 ± 0.10), while no change in diversity was detected for mulched wetlands. In a subsample of wetland sites, the concentrations of secondary macro-elements (Mg, Ca, and K) were greater in the mulched than in non-mulched wetlands. No significant differences were detected for primary nutrients (NO₃-N and P), soil pH, or above-ground plant biomass. Even 5–10 years after construction, initial mulching still seems to still have an influence on ecosystem development in these created wetlands.

Under current U.S. wetland delineation procedures, an area must have hydric soils, wetland hydrology, and hydrophytic vegetation to be considered a wetland. This study investigated the level of correlation between these three parameters on sites disturbed by humans versus relatively undisturbed sites. Based on our data set of nearly 1,800 data points from 188 sites in northeastern Illinois and northwestern Indiana, USA, relatively “disturbed” locations are significantly less likely to meet all three wetland criteria than “undisturbed” locations. Disturbance also affects an area's likelihood to meet or fail particular wetland parameters, depending on the type of disturbance. Also, areas dominated by common hydrophytic species are significantly less likely to meet all three wetland criteria in disturbed areas versus undisturbed areas. This study suggests the need for quantitative studies of the three wetland criteria on both disturbed and undisturbed sites to refine further the USFWS wetness ratings and hydric soil field indicators relative to the effects of disturbance.

Seasonal wetlands of the Swan Coastal Plain in southwestern Australia often dry in summer, refill during heavy winter rains, and are commonly surrounded by vegetated catchments. However, the linkage between catchment litter turnover and lake P dynamics is poorly understood. A transect from catchment uplands to the dry lakebed of Thomsons Lake was studied with the progression of the wet season. Attention was given to 1) levels of litter-P release at various sites; 2) spatial patterns of soil P along a wet to dry transect; and 3) dynamic changes in soil P availability in response to changing hydrologic conditions. Phosphorus detained in situ by anion exchange membranes and changes in AEM-extractable P (AEM-P) in surface soils indicated that the first heavy rainfall of the wet season generated significant P loads from catchment litter. In contrast, there was little P released in bare soils without litter. Before rain, soil AEM-P in the lakebed and fringing areas was low, but this increased by 3.4–56 times in the wet season. There was a net decrease in AEM-extractable P, total P, and organic C in the upland catchment but an increase in the wetland during the wet season. The results suggest that heavy rains after six months of drying may generate significant P flux from catchment litter. This would be followed by further leaching and an inferred stimulation of microbial activity during the progress of the wet season. The large increase in AEM-P in lake sites appears related to the input of P from catchment sites through hydrologic processes during the rains and an internal process associated with a ‘drying-rewetting’ effect.

The landscape within the Chesapeake Bay watershed has been and continues to be impacted by human modifications. Understanding if such anthropogenic disturbances influence organisms that are dependent upon estuarine wetlands remains unclear. We developed an index of marsh bird community integrity (IMBCI) to evaluate marsh bird communities and wetland condition. During the 2002 and 2003 summers, we detected 30 bird species at 219 point count locations distributed among 96 wetlands. IMBCI scores for each wetland were used to determine whether wetland habitat characteristics and urban/suburban development, agriculture, and forest at three different spatial scales (watershed, 1000-m buffer, and 500-m buffer) influenced marsh bird community integrity. We found no relationship between IMBCI scores and wetland habitat characteristics, implying that marsh bird community integrity is not related to any single plant community. Nonparametric changepoint analysis indicated that marsh bird community integrity was significantly reduced when the amount of urban/suburban development within 500 m and 1000 m of the marsh exceeded 14% and 25%, respectively. There was no effect of urban/suburban development on IMBCI scores at the watershed scale. The results of our study demonstrate that marsh bird community integrity shows a threshold response to urban/suburban development at local scales. IMBCI scores, combined with the identification of a land-use threshold, can be easy to interpret and may help communicate complex ecological data to natural resource managers and conservation planners.

Santa Olalla is a Mediterranean permanent coastal shallow lake, with high annual solar irradiation and warm water temperature throughout the year. Ecosystem metabolism, chlorophyll a concentrations, and physical and chemical features were studied in the Santa Olalla lake from March 1998 to February 2000. Gross primary productivity (GPP) and community respiration (CR) were determined using a modification of the one-station diel oxygen change method. Chlorophyll a, Secchi depth, and total phosphorous and nitrogen reveal Santa Olalla to be a hypereutrophic system. Values of GPP and CR were very high (average 7.88 g O₂ m⁻² d⁻¹ and 8.52 g O₂ m⁻² d⁻¹, respectively). Principal components analysis and a multiple regression model showed photosynthetically active radiation and soluble reactive phosphorus to be the main factors that control primary production in Santa Olalla. Also, the annual and interannual variation of water level in Santa Olalla seems to be an important factor that influences the ecological processes of this system. Mean net daily metabolism during a hydrologic period was not statistically different from 0 (0.008 g O₂ m⁻² d⁻¹, p = 0.99), and the average P/R ratio was not statistically different from 1 (1.164, p = 0.343). These results suggest that the primary productivity was balanced with community respiration in Santa Olalla lake. The high values of metabolic rates and low nutrient concentrations in this aquatic ecosystem suggest a quick recycling of nutrients, which were assimilated almost instantaneously after mineralization.

Metal tolerance in plants is thought to evolve following exposure to elevated metal levels in the soil. However, there are examples of species that appear to have developed constitutive metal tolerance without apparent exposure to metals. In previous studies, populations from contaminated and non-contaminated sites of the wetland plants Typha latifolia, Phragmites australis, and Glyceria fluitans were found to be equally tolerant to high concentrations of metals. In this study, zinc uptake and growth responses of populations of Eriophorum angustifolium, Juncus effusus, and Juncus articulatus from zinc-contaminated and non-contaminated sites were compared as part of a research project investigating metal tolerance in wetland plants. The populations were grown hydroponically in zinc-amended nutrient solutions. Juncus articulatus could not grow in the presence of elevated zinc concentrations, and no growth differences between populations were observed. Both populations of Juncus effusus from contaminated and non-contaminated sites grew well in moderately elevated zinc concentrations, but growth was inhibited at the higher treatment levels. Growth of Eriophorum angustifolium was inhibited less than growth of Juncus effusus at the higher zinc treatment levels. Both populations were able to tolerate concentrations of zinc of up to 1000 μmol L⁻¹. The findings for Juncus effusus and Eriophorum angustifolium support the theory that wetland plants tend to be tolerant to exposure to high levels of metals, but the results for Juncus articulatus suggest that this is not a general rule.

In the past century, loading of terrestrial inorganic nitrogen to coastal receiving waters has increased dramatically. Salt marshes, because of their location between upland regions and coastal waters and their recognized role as nutrient transformers, have the potential to ameliorate some of this loading. In the current study, we used core incubations in the laboratory to investigate denitrification rates in high marsh soils from five fringing salt marshes in Narragansett Bay, Rhode Island, USA. The marshes showed a wide variety of terrestrial N loading, with rates ranging from 2 to 6037 kg N ha⁻¹ yr⁻¹. Field-collected cores were selected to include both vegetated and bare soils at each marsh, and the six-hour incubations were designed to approximate natural tidal rhythms. Total dissolved nitrogen flux in these marshes ranged between 1255 and −710 μmol N m⁻² hr⁻¹, with N₂ gas accounting for the majority of the total N flux (average 76%). Nitrogen gas flux ranged between −375 (nitrogen fixation) and 420 (denitrification) μmol N₂ m⁻² hr⁻¹. While N₂ gas fluxes were significantly correlated (r = 0.64, p < 0.05) with marsh organic carbon content, we also detected a significant inverse relationship (r = −0.91, P < 0.05) between average N₂ gas fluxes and terrestrial nitrogen loads. Comparison of N₂ gas fluxes in vegetated vs. bare soils indicated a significant (p < 0.05) but variable effect of vegetation on N₂ flux. This field survey shows the potential of New England fringe salt marshes to intercept and transform land-derived nitrogen loads; however, sediment characteristics (e.g., percent of labile organic matter) and plant community structure can significantly affect the capacity of the marsh to process inorganic nitrogen loads. In order to understand the role of salt marshes in buffering coastal N loading, we need a better understanding of the natural and anthropogenic factors controlling denitrification and net N losses.

In a tidal marsh on the Savannah River (Georgia, USA), rate of plant community change along a salinity gradient was measured using a reciprocal transplant study. Donor sods were moved in all possible combinations from freshwater to brackish sites and from brackish to freshwater sites at four different locations. The reciprocal aspect of the experiment also allowed the determination of how the rate of plant community change is affected by the direction and level of displacement along the salinity gradient. Stem densities of each species were counted in each transplanted plot in June and October for a 30-month period. Plant community structure and composition changed by a significantly measurable amount within 6 to 18 months of a change in salinity. However, the time required for the transplanted sods to resemble their surrounding communities (at the p ≤ 0.05 level) ranged from 6 to more than 30 months, with some transplanted sods never resembling the surrounding plant communities during the study period. If freshwater or oligohaline sods were moved to more saline environments, environmental conditions appeared to have an overriding effect on the vegetation and community change was rapid, occurring in 6–10 months (mean = 9.3 months, SE = 1.9). Shifts from brackish to fresher sites on the salinity gradient delayed community change to about 18 months (mean = 15.3 months, SE = 1.7) and appeared to be controlled by biotic factors such as vegetative expansion and interspecific competition.

Five lagoonal salt marsh areas, ranging from 220 ha to 3,670 ha, were selected from Cape Cod, Massachusetts to the southern DelMarVa peninsula, Virginia, USA to examine the degree to which Spartina marsh area and microhabitats had changed from the early or mid- 1900s to recent periods. We chose areas based on their importance to migratory bird populations, agency concerns about marsh loss and sea-level rise, and availability of historic imagery. We georeferenced and processed aerial photographs from a variety of sources ranging from 1932 to 1994. Of particular interest were changes in total salt marsh area, tidal creeks, tidal flats, tidal and non-tidal ponds, and open water habitats. Nauset Marsh, within Cape Cod National Seashore, experienced an annual marsh loss of 0.40% (19% from 1947 to 1994) with most loss attributed to sand overwash and conversion to open water. At Forsythe National Wildlife Refuge in southern New Jersey, annual loss was 0.27% (17% from 1932 to 1995), with nearly equal attribution of loss to open water and tidal pond expansion. At Curlew Bay, Virginia, annual loss was 0.20% (9% from 1949 to 1994) and almost entirely due to perimeter erosion to open water. At Gull Marsh, Virginia, a site chosen because of known erosional losses, we recorded the highest annual loss rate, 0.67% per annum, again almost entirely due to erosional, perimeter loss. In contrast, at the southernmost site, Mockhorn Island Wildlife Management Area, Virginia, there was a net gain of 0.09% per annum (4% from 1949 to 1994), with tidal flats becoming increasingly vegetated. Habitat implications for waterbirds are considerable; salt marsh specialists such as laughing gulls (Larus atricilla), Forster's terns (Sterna forsteri), black rail, (Laterallus jamaicensis), seaside sparrow (Ammodramus maritimus), and saltmarsh sharp-tailed sparrow (Ammodramus caudacutus) are particularly at risk if these trends continue, and all but the laughing gull are species of concern to state and federal managers.

Pitfall trapping of terrestrial invertebrates in and around a seasonal woodland pond in northern Minnesota, USA revealed that large numbers of detritivorous and predaceous invertebrates from the forest floor were entering the pond as it dried. To assess the significance of terrestrial invertebrate foraging on litter processing and survival of aestivating aquatic invertebrates in dry pond basins, a small-scale exclusion study was conducted at two seasonal woodland ponds. Litter and invertebrates collected beneath pond waters were added to either 1-mm-mesh pouches (30 × 30 × 5 cm) that excluded large-bodied terrestrial invertebrates or 12-mm-mesh reference pouches that permitted entry. Pouches were left in dry basins for four weeks. Upon retrieval, I found that more aestivating aquatic invertebrates existed in exclusion than reference pouches (P < 0.001), suggesting that predation from terrestrial invertebrates might influence aquatic forms. Impacts of excluding detritivorous terrestrial invertebrates on litter processing were equivocal. I argue, however, that the influence of terrestrial invertebrates on seasonal pond ecology has rarely been considered, and it might be significant in terms of overall ecosystem function.

To identify potential constraints on willow (Salix spp.) seedling establishment in montane riparian communities in Rocky Mountain National Park, Colorado, USA we established a controlled experiment to examine the effects of soil texture and elevation above river stage on willow seedling survival. We followed seedling survival rates over two summers in paired course- and fine-textured plots established at three elevations on study area point bars. Patterns of seedling survival changed over the course of the study, and after two growing seasons, greater seedling survival rates were observed in fine-textured plots and plots occurring at high and intermediate elevations. Our results indicate that both soil water availability and scour by spring floods influence the spatial and temporal patterns of willow seedling survival on point bars along small-order montane streams.