This study investigated the role of hydrology, soils, and trampling in determining the distribution of vegetation in an isolated wetland from 1996 to 1999. Grassy Pond, in Litchfield, New Hampshire, is a seasonally flooded basin marsh situated in sandy soils. It is a depressional wetland consisting of three connected basins; it has no surface-water inlets or outlets. This acidic, low-nutrient wetland contains several rare species and represents an uncommon ecosystem type in New England. A network of wells and piezometers monitored from 1996 to1999 established that the wetland receives an average of 95.4% of its growing season inputs from precipitation and the rest from shallow ground water flowing through the wetland; as a result, it experiences large fluctuations in water levels. Vegetation in the wetland fell into five major elevation zones. Variation in plant diversity within each zone, and differences between adjacent zones, result in part from differences in depth of organic layer, trampling by hikers, all-terrain vehicles, and native wildlife, and the extent of water-level fluctuations. Several of the low basin species are more likely to be found in trampled areas. Shrub invasion of the open basin areas is prevented by trampling in some areas and by high water levels in others. Variability in hydrology resulted in temporal, as well as spatial, variability in the plant community, as dry years yielded significantly greater diversity, including a large increase in tree seedlings. Both hydrologic variability and trampling are external factors that explain a significant portion of the variation in vegetation on a large scale and connect this geographically isolated wetland to the surrounding landscape. On a smaller scale, however, autogenic forces related to soil formation and plant species interactions may be more important in explaining the plant diversity in the wetland.

Field collections during November of green-winged teal (Anas crecca), mallard (Anas platyrhynchos), and coot (Fulica atra) feces in Denmark, England, and France were used to examine the potential of waterbirds to disperse aquatic plant, algae, and invertebrate species across Europe. A total of 216 fecal samples were collected, of which 28% contained intact seeds of common wetland plants (Scirpus spp., Eleocharis spp., Chenopodium spp.), 7% contained algae oogonia (Chara spp.), and 14% contained invertebrate diapause eggs that included ephippia (Daphnia spp.) and non-ephippial eggs. Many propagules, such as Chenopodium seeds, Charophyte oogonia, and invertebrate diapause eggs, were of small size, indicating that either consumption rates or the probability to pass the gut intact is higher for smaller propagule sizes. We found averages of from 0.1 to 1.9 intact seeds and 0.1 to 0.9 intact oogonia and diapause eggs per duck or coot dropping. Our data indicate that propagules of aquatic plants, algae, and invertebrates can be deposited in feces by these waterbird species. We did not measure the viability of propagules and, therefore, have not shown that these propagules escaped digestion to the extent that viability was not altered. Although any given bird may carry few intact propagules, the thousands of waterbirds moving among wetlands collectively are potentially effective at dispersing many species of aquatic organisms.

Analysis of 38 chemical elements in five peat cores from the mid-continent to the eastern coast of North America shows that the concentrations and rates of accumulation of chemical elements supplied by atmospheric deposition to Sphagnum bog peats vary greatly with geographic location, which determines the relative importance of emissions to the atmosphere from the soil (e.g., Al, La, Th) and the sea (e.g., I., Br, Cl, Na). Biological uptake also has a considerable effect upon certain elements (e.g., C, N, K, P). The concentration/depth profiles of several lithophilic and biophilic elements reveal greater concentrations in fen than in bog peats, and in surficial than in deeper bog peats, but only in some sites. Some mobile elements are lost to a marked degree from the peat column (Na, K) or are influenced by upward migration from fen peat into the bog peat above it (Ca, Fe, Mn). No single chemical element, or elemental quotient (e.g., Ca/ Mg, C/N), clearly distinguishes the transition from fen to bog peat in all sites.

New England salt marsh pools provide important wildlife habitat and are the object of on-going salt marsh restoration projects; however, they have not been quantified in terms of their basic geomorphic and geographic traits. An examination of 32 ditched and unditched salt marshes from the Connecticut shore of Long Island Sound to southern Maine, USA, revealed that pools from ditched and unditched marshes had similar average sizes of about 200 m², averaged 29 cm in depth, and were located about 11 m from the nearest tidal flow. Unditched marshes had 3 times the density (13 pools/ha), 2.5 times the pool coverage (83 m pool/km transect), and 4 times the total pool surface area per hectare (913 m² pool/ha salt marsh) of ditched sites. Linear regression analysis demonstrated that an increasing density of ditches (m ditch/ha salt marsh) was negatively correlated with pool density and total pool surface area per hectare. Creek density was positively correlated with these variables. Thus, it was not the mere presence of drainage channels that were associated with low numbers of pools, but their type (ditch versus creek) and abundance. Tidal range was not correlated with pool density or total pool surface area, while marsh latitude had only a weak relationship to total pool surface area per hectare. Pools should be incorporated into salt marsh restoration planning, and the parameters quantified here may be used as initial design targets.

Benthic Chironomidae were studied in two shallow, brackish, eutrophic wetlands in Alicante province in eastern Spain (Levante lake in El Hondo Natural Park and Múrtulas ponds in Santa Pola Natural Park). Core samples were taken monthly from eight points in each site from March to August 1999. Levante was more eutrophic, less saline, and held more and larger chironomid larvae than Múrtulas. Larvae of six taxa were identified at Levante and five at Múrtulas. Chironomus aprilinus and C. salinarius morphotypes dominated at Levante, whereas Tanytarsus spp. and C. salinarius dominated at Múrtulas. In generalized linear models, there were significant effects of site, month, and site X month interactions on larval size at both family and taxon levels. On average, C. salinarius larvae were larger at MUR, probably due to a lower proportion of smaller instars and lower growth rates. Although the overall trend was for a reduction in mean larval size over time in both wetlands, mean size peaked in March at Levante and in May at Múrtulas.

A central tenet of wetland mitigation is that replacement wetlands can sequester nutrients and perform other functions at the same level as natural wetlands. This study evaluated phosphorus (P) sorption capacity and P exchange in flooded soil microcosms obtained from eight early successional (ES) mitigated and eight late successional (LS) bottomland forest wetlands in western Kentucky, USA. The LS soils had three times greater capacity to remove and retain soluble inorganic P than ES soils, which was mostly due to higher amounts of amorphous aluminum (Al) oxides (oxalate extractable), organically-bound Al (CuCl₂ extractable), and organic carbon in LS soils. Phosphorus exchange rates between the soil and water column were not significantly different in LS and ES microcosms, but rates in both systems were strongly related to the molar ratio of Mehlich III extractable P to Al Fe in the soil (r²=0.64). Relationships between P sorption/exchange and organic C, Mehlich III- and oxalate-extractable forms of P, Al, and Fe determined in this study could be useful for (i) identifying suitable mitigation sites that would be P sinks rather than P sources to the water column and (ii) determining replacement ratios that would fairly compensate for P retention capacity losses caused by destruction/alteration of Kentucky bottomland hardwood forest wetlands.

Aquatic vascular plants, or macrophytes, are an important habitat component for many wetland organisms, and larvae of chironomid midges are ubiquitous components of wetland fauna. Many chironomids are primary consumers of algae and detritus and form an essential energetic link between allochthonous and autochthonous primary production and higher trophic levels, while others are predators and feed on smaller invertebrates. Live macrophytes serve mostly as habitat, whereas plant detritus serves as both habitat and as a food source. Assemblages of macrophytes and chironomid larvae were surveyed in ten Maine wetlands, five with low pH (<5.0) and five with high pH (>5.5), and explained in terms of physical and chemical habitat variables. Macrophyte richness was significantly greater, and richness of chironomid larvae was lower, in low pH wetlands. There was no difference in chironomid abundance related to pH. However, community structure was related to pH, suggesting that competitive dominance of a few taxa was responsible for lower richness in low pH wetlands, whereas competition was weaker in high pH wetlands, making coexistence of more chironomid taxa possible. An examination of individual chironomid taxa by stepwise multiple regression showed that distribution of most taxa was controlled by water chemistry variables and macrophyte habit (i.e., floating, submergent).

Although considerable attention has been focused on competition among wetland plants, surprisingly few studies have considered the role of facilitation in structuring freshwater wetland plant assemblages. Positive interaction among plants has been investigated thoroughly in saline marshes, which display a definite, predictable pattern of species zonation, with facilitation playing an important role during colonization of bare or disturbed patches of marsh. The few studies that have investigated facilitation in freshwater marshes have implicated the processes of sediment oxygenation and sediment stabilization. Whereas both processes are known to be influenced by many freshwater hydrophyte species, they have not been considered widely as mechanisms of interspecific facilitation. In the tussock-forming rush Juncus effusus L., late-Spring collapse of culms away from the tussock center results in a morphology that increases light availability atop tussocks and appears to establish a unique spatio-temporal component to the effect of Juncus on neighbors. In previous work, shading around the tussock periphery, influenced largely by this collapse of culms, was shown to suppress production and species richness of neighbors; however, various plant species have been observed to grow directly upon the Juncus tussocks in the void left by collapsed culms. To quantify this latter phenomenon, vascular plant abundance was evaluated on tussocks of Juncus effusus in four Mississippi (USA) beaver wetlands to determine the likelihood and nature of positive interactions between Juncus and neighbors. Tussocks in three of these wetlands were examined for tussock microtopography and diameter, relative water depth atop the tussock, and colonization by other plant species. Species richness of colonizing plants correlated positively with tussock diameter in two of these wetlands, and no colonizers were present in the third. Tussock microtopography and elevation differed significantly among wetlands, but species richness was unrelated to relative water depth atop the tussocks. In the fourth beaver marsh, two sets of surveys were conducted to determine whether the species assemblages upon Juncus tussocks differed from those across the entire wetland. Plant assemblages on Juncus tussocks, and on elevated substrata in general, were significantly different from assemblages not associated with elevated surfaces. Thirteen species were associated exclusively with elevated rooting substrata, ten of which were exclusive to Juncus effusus tussocks. The present results suggest that small-scale spatial and temporal shifts occur in the effects of Juncus on neighboring plants. Effects shift from primarily competitive shading interactions resulting from a dense shoot canopy to facilitative interactions atop tussock mounds after mature culms collapse. Facilitation likely is mediated through characteristics of the tussock mound, such as provision of a stable rooting substratum or oxygenation of sediments by the Juncus effusus root system.

We assessed the sensitivity of a viviparous estuarine tree species, Rhizophora mangle, to historic sublethal mutagenic stress across a fine spatial scale by comparing the frequency of trees producing albino propagules in historically contaminated (n=4) and uncontaminated (n=11) forests in Tampa Bay, Florida, USA. Data from uncontaminated forests were used to provide estimates of background mutation rates. We also determined whether other fitness parameters were negatively correlated with mutagenic stress (e.g., degree of outcrossing and numbers of reproducing trees km⁻¹). Contaminated sites in Tampa Bay had significantly higher frequencies of trees that were heterozygous for albinism per 1000 total reproducing trees (FHT) than uncontaminated forests (mean ± SE: 11.4 ± 4.3 vs 4.3 ± 0.73, P<0.022). Two sites that were contaminated by oil failed to show elevated FHT, although in the first instance, the mutagenic effects of the oil may have been reduced by several weeks of weathering in open water before coming ashore, and in the second > 25 yrs of subsequent recruitment and tree replacement may have allowed an initial elevation in the FHT to decay. Patterns of FHT were not explained by distance from the bay mouth or the degree of urbanization. However, there was a significant positive relationship between tree size and FHT (r=0.83, P<0.018), which suggests that forests with older or larger trees provide a more lasting record of cumulative mutagenic stress. No other fitness parameters correlated with FHT. There was a difference in FHT between two latitudes, as determined by comparing Tampa Bay with literature values for Puerto Rico. The sensitivity of this bioassay for the effects of mutagens will facilitate future monitoring of contamination events and comparisons of bay-wide recovery in future decades. Development of a database of FHT values for a range of subtropical and tropical estuaries is underway that will provide a baseline against which to compare mutational consequences of global change.

Missouri Coteau prairie glacial wetlands are subject to numerous anthropogenic disturbances, such as cultivation, construction, and chemical inputs from upland land-use practices. High wetland density and temporal variability among these ecosystems necessitate synoptic tools for watershed-scale wetlands assessment and comprehensive monitoring. We developed a Geographic Information Systems (GIS) classification model for Missouri Coteau prairie glacial wetlands in North Dakota, USA and derived two indices that provide data salient to landscape-scale wetland assessment and monitoring. One, the Basin Buffer Index (BBI), delineates areas of natural vegetation that buffer waters from anthropogenic disturbance. The second, the Hydric Vegetation Index (HVI), delineates areas of hydric vegetation communities essential to prairie glacial wetland function. The model was developed by spectrally characterizing structural attributes common to glacial basins, such as hydroperiod, canopy architecture, and plant life-form and evaluating the potential for spectral detection of the natural vegetation buffers that surround these wetlands. Spectral separation among community zones in the green, red, and mid-infrared regions were evident in hyperspectral data and were convolved to fit multi-spectral satellite sensors. Model application using Landsat ETM and SPOT 5 satellite data over the central North Dakota study area produced classifications for buffer delineation and hydric community detection with 89 and 85% accuracy, respectively. By integrating remote sensing technology with those structural factors fundamental to wetland quality (i.e., land-use and natural vegetation buffers surrounding water bodies), we illustrate a method for evaluating wetland condition at a landscape scale.

This study was carried out in a Mediterranean salt marsh in semiarid Southeast Spain to assess whether a spatial salinity gradient can affect the microbiological and biochemical properties (labile C fractions, biomass C, oxidoreductases, and hydrolases) of the rhizosphere soil of Inula crithmoides and the extent of arbuscular mycorrhizal (AM) colonization in its roots. There were no significant differences in the soluble C fractions (water-soluble C and water-soluble carbohydrates) or the microbial biomass C values of the rhizosphere soil of I. crithmoides among the different zones of the salt marsh. Dehydrogenase activity, hydrolases (urease, protease, phosphatase, and β-glucosidase) and the extent of AM colonization in I. crithmoides roots were greater in the higher salt marsh zones, corresponding to those of lower rhizosphere soil salinity. This study shows that soil salinity is inversely associated with some parameters related to soil microbial activity, such as dehydrogenase activity and some hydrolases, as well as the extent of colonization by AM fungi, which can improve plant performance. However, bioactive organic matter fractions that determine soil productivity are not related to soil salinity.

Species composition in floodplain vegetation is often related to initial floristics, succession, and disturbances such as flooding and herbivory. However, on a braided, cobble-bedded river with contrasting sediment facies, much of the composition of understory vegetation within a cottonwood forest was related to edaphic factors controlled by stream-deposit stratigraphy. Large shifts in understory species composition were more related to soil texture and water availability than deposit age or hydroperiod. Finer-textured and thicker overbank deposits had greater water availability and supported mesic species, while sites with coarse sediments to the surface supported only xeric species. A strong gradient of site moisture corresponded to a gradient in species composition. Soil water potential (Ψ_s) indicated by pre-dawn xylem water potential (XWP_PD) in a shallow-rooted grass reached −4.2 MPa on xeric-species sites in mid-summer; on mesic-species sites, XWP_PD was always greater than −1.5 MPa for the same grass species. Deep-rooted plants had a narrower range of XWP_PD across all sites, and XWP_PD was typically between 0.0 and −1.0 MPa. Ψ_s derived from actual soil water content followed the same pattern indicated by species composition, soil texture, and XWP_PD.

We evaluated the effect of four hydraulic retention times (HRT, 0.3, 0.8, 2.3, and 9.3 days) on pollutant removal in a surface-flow wetland system for polishing tertiary effluent from a sewage treatment plant (STP). The removal efficiency of pollutants at these HRTs was based on mass budgets of the water inputs and outputs in parallel ditches, which together with a presettling basin, made up the wetland system. Fecal coliform and N-removal efficiencies in the ditches were enhanced by increasing the HRT, with only little removal of fecal coliforms during spring-summer at a HRT of 0.3 days. A HRT of 4 days turned out to be required to meet the desired bathing water standard for fecal coliforms (10³ cfu 100 ml⁻¹) and the future standard of ammonium (1 mg N l⁻¹) all year. An annual N-removal efficiency of approximately 45% can be accomplished in the ditches at this HRT, corresponding to an annual N mass loading rate of 150 g N m⁻² yr⁻¹. Annual P removal was not improved by increasing the HRT even up to 9.3 days, largely because of the still high P mass loading rate (14 g P m⁻² yr⁻¹) in combination with relatively low P input concentrations. Substantial P removal can probably only be achieved at HRTs longer than 15 days, which will not be feasible for the situation investigated because of the large land area that would be required to reach such long HRTs. The future P standard (1 mg P l⁻¹) can therefore only be met by additional chemical P removal. In a densely populated country such as the Netherlands, adequate polishing of tertiary STP effluent in surface-flow wetlands with similar goals as for this wetland is restricted to small and medium-sized STPs. The simultaneous use of these treatment wetlands for other functions, such as nature conservation, recreation, and flood control, however, would permit the use of relatively larger land areas.

Although seed dispersal is assumed to be a major factor determining plant community development in restored wetlands, little research exists on density and species richness of seed available through dispersal in these systems. We measured composition and seed dispersal rates at a restored tidal freshwater marsh in Washington, DC, USA by collecting seed dispersing through water and wind. Seed dispersal by water was measured using two methods of seed collection: (1) stationary traps composed of coconut fiber mat along an elevation gradient bracketing the tidal range and (2) a floating surface trawl net attached to a boat. To estimate wind dispersal rates, we collected seed from stationary traps composed of coconut fiber mat positioned above marsh vegetation. We also collected a small number of samples of debris deposited along high tide lines (drift lines) and feces of Canada Goose to explore their seed content. We used the seedling emergence method to determine seed density in all samples, which involved placing the fiber mats or sample material on top of potting soil in a greenhouse misting room and enumerating emerging seedlings. Seedlings from a total of 125 plant species emerged during this study (including 82 in river trawls, 89 in stationary water traps, 21 in drift lines, 39 in wind traps, and 10 in goose feces). The most abundant taxa included Bidens frondosa, Boehmeria cylindrica, Cyperus spp., Eclipta prostrata, and Ludwigia palustris. Total seedling density was significantly greater for the stationary water traps (212±30.6 seeds/m²/month) than the equal-sized stationary wind traps (18±6.0 seeds/m²/month). Lower-bound estimates of total species richness based on the non-parametric Chao 2 asymptotic estimators were greater for seeds in water (106±1.4 for stationary water traps and 104±5.5 for trawl samples) than for wind (54±6.4). Our results indicate that water is the primary source of seeds dispersing to the site and that a species-rich pool of dispersing propagules is present, an interesting result given the urbanized nature of the surrounding landscape. However, species composition of dispersing seeds differed from vegetation of restored and natural tidal freshwater marshes, indicating that planting is necessary for certain species. At other restoration sites, information on densities of dispersing seeds can support decisions on which species to plant.

The coterminous U.S. has lost more than 50% of its wetlands since colonial times. Today, wetlands are highly valued for many functions including temporary storage of surface water, streamflow maintenance, nutrient transformation, sediment retention, shoreline stabilization, and provision of fish and wildlife habitat. Government agencies and other organizations are actively developing plans to help protect, conserve, and restore wetlands in watersheds. The U.S. Fish and Wildlife Service's National Wetlands Inventory Program (NWI) has produced wetland maps, digital geospatial data, and wetland trends data to aid these and other conservation efforts. Most recently, the NWI has developed procedures to expand the amount of information contained within its digital databases to characterize wetlands better. It has also developed techniques to use these data to predict wetland functions at the watershed level. Working with the states of Delaware and Maryland, the NWI applied these techniques to the Nanticoke River watershed to aid those states in developing a watershed-wide wetland conservation strategy. Wetland databases for pre-settlement and contemporary conditions were prepared. An assessment of wetland functions was conducted for both time periods and comparisons made. Before European settlement, the Nanticoke watershed had an estimated 93,000 ha of wetlands covering 45% of the watershed. By 1998, the wetland area had been reduced to 62% of its original extent. Sea-level rise and wetland conversion to farmland were the principal causes of wetland loss. From the functional standpoint, the watershed lost over 60% of its original capacity for streamflow maintenance and over 35% for four other functions (surface-water detention, nutrient transformation, sediment and particulate retention, and provision of other wildlife habitat). This study demonstrated the value of enhanced NWI data and its use for providing watershed-level information on wetland functions and for assessing the cumulative impacts to wetlands. It provides natural resource managers and planners with a tool that can be applied consistently to watersheds and large geographic areas to show the extent of wetland change and its projected effect on wetland functions.

Post-restoration wetland sites often do not resemble natural wetlands in diversity or richness of native species, in part due to the influence of stressors such as excess contaminant loads and invasive species. Road salt and the salt-tolerant invasive Typha angustifolia are potential wetland stressors for which little is known, although it is thought that high salt contaminant loads can lead to invasion of a plant community by T. angustifolia. To understand how an establishing freshwater wetland community responds to NaCl, with regard to both direct and indirect effects (indirect mediated by competition with T. angustifolia), an assemblage of native marsh species was grown from seed in greenhouse microcosms and subjected to treatments of NaCl (0, 100, 250, 500, and 1000 mg·L⁻¹ solutions) and T. angustifolia (with and without T. angustifolia seed additions) for 194 days. Direct effects of NaCl on final biomass of the native assemblage were observed in the 500 and 1000 mg·L⁻¹ NaCl treatments. Indirect effects of NaCl on final biomass were observed in the 1000 mg·L⁻¹ NaCl treatment. Diversity and species richness decreased slightly with increasing NaCl concentration. Evenness increased slightly with increasing NaCl concentration. Individual species responded differently to NaCl and T. angustifolia, suggesting that species composition plays an important role in determining the extent to which NaCl and T. angustifolia influence native community establishment. Results from this experiment suggest that road salt runoff should be considered a stressor during site selection and that restoration of sites exposed to high levels of NaCl may be less diverse or contain an assemblage of species different than that intended.

Elevated CO₂ generally stimulates C₃-type photosynthesis, but it is unclear how an increase in CO₂ assimilation will interact with other factors that influence plant growth. In wetlands, the response of plants to elevated CO₂ will interact with soil saturation, particularly in forested wetlands where soil saturation is a strong regulator of plant productivity. We performed a four-month experiment to determine whether elevated CO₂ and flooding interact to influence the growth of a flood-tolerant tree (Taxodium distichum) and a flood-tolerant herbaceous emergent macrophyte (Orontium aquaticum). Seedlings were grown in glasshouses at two CO₂ levels (350 and 700 μL L⁻¹) crossed with two water depths (5 cm above and ≥5 cm below the soil surface). We hypothesized that elevated CO₂ would increase photosynthesis regardless of water depth and species; however, we also expected flooding to prevent elevated CO₂ from increasing the growth of the tree species due to O₂ limitation or other physiological stresses associated with reduced soil environments. We found that elevated CO₂ increased whole-plant photosynthesis in both species regardless of the flooding treatment. For T. distichum, this higher photosynthetic rate resulted in greater biomass only in the non-flooded treatment. This result suggests that some factor related to flooding constrained the biomass response of the flooded woody plants to elevated CO₂. In contrast, elevated CO₂ increased O. aquaticum biomass regardless of the flooding regime, perhaps because it occurs in wetter landscape positions than T. distichum and is less sensitive to flooding. We conclude that flooding may limit plant growth responses to elevated CO₂, particularly in woody plant species.

While intensified nutrient limitation of periphyton has been reported along wetland nutrient-depletion gradients, changes to the specific nutrient that limits periphyton growth are not documented. In this study, we used artificial nutrient-diffusing substrata to determine nutrient limitation status of periphyton along a nitrogen- and phosphorus-depletion gradient in a freshwater marsh during the growing season of 2003. We also characterized water-column nutrient content, N:P ratio of dissolved nutrients, and periphytic N₂ fixation potential along the gradient. Dissolved inorganic nitrogen concentrations consistently decreased (60% − 95%) from inflow to outflow during all bioassays, while soluble reactive phosphorus concentrations decreased during the April (49%) and September (39%) bioassays but increased in the July bioassay (51%). Unequal N and P retention resulted in a general decrease in DIN:SRP mass ratio from 20.2 ± 5.0 to 3.8 ± 1.6 between inflow and outflow, respectively. Periphyton at the wetland inflow never responded to N additions alone, while periphyton at the outflow always responded to N enrichment. Periphyton at the inflow were either not limited by nutrients (September) or co-limited by N P (April and July). At the outflow, periphyton were either N-limited (April and September) or strongly co-limited by N P (July). A significant increase in N₂ fixation potential (p < 0.05) from inflow to outflow locations was noted for all measured events. Our results suggest that, in addition to the severity of nutrient limitation, some wetlands may display spatial heterogeneity in the specific nutrient that limits periphyton growth. Further, these shifts influence the structure and function of wetland periphyton assemblages.

To clarify the nutrient dynamics in peat-covered watersheds during frost, soil, chemical properties of atmospheric deposition (bulk deposition and throughfall) on mires, peat pore water, and stream-water outflows from mires were investigated at three ombrogenous mires with Picea glehnii M. forests and Sphagnum spp. communities in Ochiishi, eastern Hokkaido, Japan. We investigated the depth of frozen ground as one of the factors determining chemical properties of outflowing stream water from mires. Na and Cl⁻ were the dominant ion species in bulk deposition and throughfall, implying the influence of sea salts on precipitation chemistry. The electrical conductivity (EC) and Na , Mg² Ca² , Cl⁻, and SO₄²⁻ concentrations in throughfall (snow) were 5–10 times higher than bulk deposition after a 25-day period without precipitation in February 2001. Throughfall was enriched with sea salts from dry deposition on the canopy, while snow was intercepted by the forest canopy. The first rain event during the seasonal soil freezing led to the enrichment of chemical components in the stream-water outflows from the mire. The frozen layer in the upper peat soil prevented the infiltration of snow melt into peat soil during the period of frost soil, and hence large amounts of salts (Na and Cl⁻) accumulated on the snow surface or within the snow cover. Rain water flowed over the frost soil layer and was enriched with chemicals from accumulated salts in the snow cover. This subsequently led to the high salt concentration in stream water just after the rain events during the season when soil was frozen.

Wetlands provide critical wildlife habitat in the central Platte River basin of Nebraska, USA, but little is known about their macroinvertebrate communities or how factors such as hydrology affect them. In 1997, we quantified macroinvertebrate abundance, biomass, and community structure and organic matter resources in four natural wetlands that represented a gradient from ephemeral to permanent flooding. All four wetlands had abundant macroinvertebrate communities when flooded, and we observed unique taxa at all sites. Mean annual macroinvertebrate abundance and biomass increased with hydroperiod length, but taxon richness and diversity were greatest in intermittent sites. Non-insect groups, mostly crustaceans, annelids, and mollusks, were important at all sites, and their taxonomic composition shifted across the hydrologic gradient. Insect communities were dominated by dipterans (mostly Chironomidae and Ceratopogonidae) and Coleopterans (mostly Hydrophilidae and Dytiscidae), and these also varied across the hydrologic gradient. Collector-gatherers, scrapers, and predators were the dominant functional groups in terms of biomass, and biomass was most evenly distributed among these groups in intermittent sites. Macroinvertebrate communities in these riparian wetlands vary across natural hydrologic gradients, and diversity peaks in intermittent sites. Patterns of abundance, biomass, and diversity, along with seasonal patterns, suggest that, at a landscape level, a diversity of wetland habitats with different hydrologic regimes will maximize abundance and diversity of freshwater macroinvertebrate communities in this region.

The importance of fungi and bacteria attached to leaf litter in the diet and growth of shredders in flowing waters is well-documented. This study focuses on the role of microorganisms colonizing submerged leaf litter in the diet and growth of Verger cf. limnophilus (Trichoptera: Limnephilidae) larvae in a Patagonian Andean temporary pond (Fantasma pond, 41°07′S, 71°27′W). First, the feeding habits were analyzed through an experiment that compared consumption of CPOM and FPOM. Once we determined that V. cf. limnophilus consumed CPOM, we performed an experiment to compare consumption and growth rates of larvae fed on non-autoclaved and autoclaved decaying leaves. Algae was the most abundant group to colonize leaf surface, comprising 74% of total biovolume. Consumption of non-autoclaved leaves was four-fold that of autoclaved treatments, which produced negative insect growth rates. Although V. cf. limnophilus processed leaves by shredding, microorganisms living on the leaf litter were found to be an important food resource. As microbial biomass represents a small percentage of the ingested food (0.22 %), V. cf. limnophilus appears to process relatively large quantities of detritus to obtain sufficient resources for growth (100 mg leaves to grow 3 mg).

Vernal pool wetlands are at risk of destruction across the northeast United States, due in part to their diminutive size and short hydroperiods. These characteristics make it difficult to locate vernal pool habitats in the landscape during much of the year, and no efficient method exists for predicting their occurrence. A logistic regression procedure was used to identify large-scale variables that influence the presence of a potential vernal pool, including surficial geology, land use and land cover, soil classification, topography, precipitation, and surficial hydrologic features. The model was validated with locations of field-verified vernal pools. The model demonstrated that the probability of potential vernal pool occurrence is positively related to slope, negatively related to till/bedrock surficial geology, and negatively related to the proportion of cropland, urban/commercial, and high density residential development in the landscape. The relationship between vernal pool occurrence and large-scale variables suggests that these habitats do not occur at random in the landscape, and thus, protection in situ should be considered.

During a broad study of invertebrate colonization in marginal fluvial wetlands of the Middle Paraná River in Argentina, cyst formation was observed in two of the 26 species of aquatic oligochaetes identified from the study—Dero multibranchiata Steiren, 1892 (Tubificidae, Naidinae), and Trieminentia corderoi (Harman, 1969) (Opistocystidae). All specimens of the two species in which cyst formation was observed had been collected after drying conditions ranging from 14 to 28 days. A clitellum was not observed in any of the specimens collected. Lengths of specimens ranged from 0.88 mm to 2.84 mm in Dero multibranchiata and 2.25 mm to 2.40 mm in Trieminentia corderoi. The development of protective cysts by Dero multibranchiata and Trieminentia corderoi, and perhaps many other species of aquatic oligochaetes, appears to be an adaptive strategy enabling them to survive drought in temporary wetlands, recolonize freshwater habitats upon inundation, and disperse both laterally and downstream with rising water levels in wetlands and streams.

Saxicolous lichen trimlines are relatively level and distinct transition zones found on bedrock-lined shores. They occur as a result of disturbance to the rock lichen community, typically due to high water events. Trimlines can inform about previous high water conditions, and in conjunction with lichenometry, can be dated. In wetlands which fluctuate in water level, dated trimlines may be useful in reconstruction of the timing and magnitude of former high water. We assessed seven common northern saxicolous lichen species over a period of 270 days to determine the period of immersion required for mortality. Overall mortality rates increased after about 30 days of immersion. At 90 days, mean mortality was about 68%; at 180 days, mean mortality was about 91%; total mortality of the immersed lichens was observed at day 270. There were large interspecific differences in susceptibility to immersion. Phaeophyscia sciastra was the least susceptible to immersion and Xanthoparmelia somloënsis was the most susceptible to immersion. A prolonged period of high water (months, rather than days) may be required to form a trimline in a northern delta. A northern saxicolous trimline might remain visually distinct for several decades in the absence of disturbance.