Typha species are increasingly considered invasive weeds in wetlands of eastern North America. Typha angustifolia and T. x glauca are often seen as more invasive than T. latifolia, but there are few comparative biogeographic data on these three species. We examined 1,127 Typha specimens archived in major herbaria to map changes in the distributions of these species since the late-19th century. We also analyzed pollen records from the North American Pollen Database (NAPD) to examine longer-term trends in abundance of each Typha species. Proportion curves comparing the relative spread of T. angustifolia and T. latifolia reveal a period of enhanced range increase in T. angustifolia in the early to mid-20th century. From the mid-20th century onwards, the two species increased at the same rate. The relatively higher rate of spread in T. angustifolia levels off after 1930 in the more coastal region of New England, but does not stop increasing inland and in more northern regions such as Ontario until after 1970. Pollen data suggest that 80% of relevant sites in the North American Pollen Database showed an increase in the abundance of one or both Typha species over the past 1,000 years. However, there was no significantly greater increase in one type of pollen compared to the other. Typha-type pollen grains in the form of tetrads and monads are recorded in the database throughout the Holocene and late Pleistocene; however, few studies analyzed the morphology of the pollen grains sufficiently to allow for positive identification of T. angustifolia. In the few recent records that made those measurements, small numbers of pre-settlement incidences of T. angustifolia and T. x glauca are recorded. Pollen and herbarium data suggest that T. angustifolia may have been present in North America prior to European settlement, but was not widespread. Herbarium data confirm that the range increase has been considerably larger in T. angustifolia than in T. latifolia since 1880, but both Typha species have been increasing at the same rate for the past several decades, and both will continue to display invasive tendencies in disturbed wetlands.

Carolina bays and similar depression wetlands of the U.S. Southeastern Coastal Plain have hydrologic regimes that are driven primarily by rainfall. Therefore, climate fluctuations such as drought cycles have the potential to shape long-term vegetation dynamics. Models suggest two potential long-term responses to hydrologic fluctuations, either cyclic change maintaining open emergent vegetation, or directional succession toward forest vegetation. In seven Carolina bay wetlands on the Savannah River Site, South Carolina, we assessed hydrologic variation and vegetation response over a 15-year period spanning two drought and reinundation cycles. Changes in pond stage (water depth) were monitored bi-weekly to monthly each year from 1989–2003. Vegetation composition was sampled in three years (1989, 1993, and 2003) and analyzed in relation to changes in hydrologic conditions. Multi-year droughts occurred prior to the 1989 and 2003 sampling years, whereas 1993 coincided with a wet period. Wetland plant species generally maintained dominance after both wet and dry conditions, but the abundances of different plant growth forms and species indicator categories shifted over the 15-year period. Decreased hydroperiods and water depths during droughts led to increased cover of grass, upland, and woody species, particularly at the shallower wetland margins. Conversely, reinundation and longer hydroperiods resulted in expansion of aquatic and emergent species and reduced the cover of flood-intolerant woody and upland species. These semi-permanent Upper Coastal Plain bays generally exhibited cyclic vegetation dynamics in response to climate fluctuation, with wet periods favoring dominance by herbaceous species. Large basin morphology and deep ponding, paired with surrounding upland forest dominated by flood-intolerant pines, were features contributing to persistence of herbaceous vegetation. Drought cycles may promote directional succession to forest in bays that are smaller, shallower, or colonized by flood-tolerant hardwoods.

Modern extraction methods permit peat to be extracted to the minerotrophic layer of ombrotrophic peatlands (bogs). As the environmental conditions of these harvested peatlands are similar to minerotrophic peatlands (fens), such sites should be restored towards a fen system. However, it is not known whether fen species would recolonize such harvested sites on their own. We surveyed vegetation and environmental variables in 28 harvested peatlands with minerotrophic residual peat across Canada and in Minnesota, USA, and compared them to 11 undisturbed fens. Compared to harvested bogs previously studied, the harvested fens sampled in this study revegetated remarkably quickly (50%–70% vegetation cover) when the hydrological conditions were suitable. However, revegetation was less extensive for sites that were still drained (25% vegetation cover). A high water table and a thin layer of residual peat were the most important factors contributing to rapid recolonization rates. Although the harvested fens were rapidly recolonized, species composition was not the same as observed on undisturbed fens. Carex and Sphagnum, dominant in undisturbed fens, generally did not recolonize harvested fens. Thus, whether the goal is to increase species richness or to ensure the return of peat accumulating functions, fen species may have to be actively introduced.

We compared benthic community structure among stands of Typha angustifolia (narrow-leaf cattail) and herbicide-treated (Glypro) and untreated Phragmites australis (common reed) over two summers in a Lake Erie coastal wetland (i.e., drowned river mouth). Both macrophytes are invasives, but only Phragmites is currently controlled by herbicides because of its reputed “undesirable” effects on wetland community structure and function. Macroinvertebrate diversity was similar among stand types and relatively high (Shannon-Weaver indices ∼2.6–4.2), probably because of high system primary productivity and a mix of lentic and riverine species. Proportions of macroinvertebrate functional feeding groups were also similar, but Jaccard's similarity indices were relatively low (29%–57%), suggesting macroinvertebrate compositional differences among stand types. Coleopterans particularly affected species presence/absence patterns, but their presence was associated with low water level rather than hydrophyte type per se. Moreover, total macroinvertebrate densities were greater in both Phragmites treatments than in Typha; a pattern generated mostly by gastropods (≥ 95% Gyraulus deflectus and Physella gyrina) and chironomids. Microalgal food supply likely plays a part in explaining these density differences, given diatom-dominated epiphyton was denser on submerged shoots of Phragmites than on Typha. Common diatom assemblages were similar among stand types, but species richness was significantly greater on untreated-Phragmites than on herbicide-treated, early senescent Phragmites and untreated-Typha. However, advanced senescence from herbicide application (∼3 months) did not apparently affect macroscale habitat suitability and structure above and below the waterline, given counts of ovipositing odonates (mostly Ischnura and Enallagma) and captures of juvenile fishes (> 90% Lepomis spp.) were similar among stand types. Overall, our results suggest that benthic community structure is comparable between similarly-aged stands (∼4 yrs old) of invading reed and cattail and is not directly or indirectly affected by Glypro application.

A watershed-based assessment of wetland impacts and compensatory mitigation was conducted for the Cuyahoga River Watershed (CRW) in northeastern Ohio, USA, to explore the effectiveness of wetland mitigation regulations and any resulting cumulative changes to wetland and landscape structure. Mitigation projects from 23 Section 401 certifications and Ohio Isolated Wetland permits were evaluated for permit compliance, wetland structure, and landscape context. Although there was a net gain in wetland area as a result of the 23 permits, the CRW experienced a net loss of wetland acreage due to the exportation to mitigation banks located outside the watershed. The majority of projects (67%) that restored or created wetlands independently (not at a mitigation bank) were not successful at meeting permit requirements in terms of wetland area. The comparison of impacted and mitigation wetland vegetation types revealed an increase in open-water/emergent wetland area and a decrease in area of scrub/shrub and forested wetlands, along with a decrease in the number of wetlands from 134 impacted wetlands to 65 mitigation wetlands. Impacted wetlands were significantly smaller than replacement wetlands. Landscape composition surrounding the wetlands was highly variable, varying from 17%–75% natural land uses and from 18%–82% human land uses. We suggest that an improvement in compliance with permit requirements is necessary. Current wetland policy allows for the exportation of wetlands for mitigation purposes, which can result in the loss of wetlands from some hydrologic units. The consideration of wetland structure needs to be incorporated into the regulatory process to avoid a shift in wetland types that are present. Finally, instead of reviewing projects on a site-by-site basis, a landscape approach should be taken in order to avoid the loss of upland-wetland heterogeneity and the placement of mitigation wetlands in degraded landscapes.

Delineation of Ordinary High Water (OHW) under the Clean Water Act (CWA) is based on the use of physical features that represent “ordinary” levels of ponding or flowing waters. On arid western United States playas, where the climate is an unevenly distributed series of precipitation events that are spread over many years, the use of surface water monitoring can be limiting due to occasional years with almost no hydrological information. To substitute for a general lack of monitored surface water conditions, we used processed satellite images and precise topographic modeling to determine ponded water areas. To test the reliability of select field indicators for delineation purposes, we used a two-phase field test on a hard playa in the Mojave Desert, California. First, we verified that ponded water was associated with these playa surface features. Then, to test the statistical reliability of these surface features, we developed a decile ponding zone map by stacking processed satellite imagery, collected detailed laser altimetry (LiDAR) elevation data, sampled surface features occurring in the various decile zones, and developed reliability statements for these OHW delineation features. These field indicators represent surface features that have developed over a series of years representing the wetter portion of the El Niño climatic cycle.

We evaluated the effectiveness of constructed wetlands with varying plant communities for phosphorus (P) reduction from the Everglades Agricultural Area runoff in south Florida. Weekly or biweekly water samples from the inflow and outflow regions of 11 test cells (2,000 m²) were analyzed for various forms of P and other selected water quality variables between January 2002 and August 2004. Test cells located at the north site received water with a high average total P (TP) concentration (72 µg L⁻¹), while test cells located at the south site received water with a lower average TP concentration (43 µg L⁻¹). These test cells were dominated by an emergent vascular plant-cattail (Typha latifolia), submerged aquatic vegetation or SAV (Najas guadalupensis, Chara sp., Ceratophyllum demersum, and Hydrilla verticillata), or algal periphyton (mixed with Eleocharis cellulosa and Utricularia spp. in the south site only). Under a constant hydraulic loading rate (9.27 m yr⁻¹), these test cells removed P effectively, with removal efficiencies of 56%–65% at the north site and 35%–62% at the south site. The mass removal rate and rate constant at the north site were also higher than at the south site. Soluble reactive P (SRP) and particulate P were the major forms at inflow and were removed effectively by all of the test cells. The removal of dissolved organic P was significant (∼60%) in the cattail and periphyton test cells, but no removal was detected in the SAV test cells. At the north site, P removal efficiency of the cattail test cells was slightly higher than that of the SAV test cells. At the south site, periphyton test cells were the best performers. The removal of SRP was positively correlated with the removal of calcium in the majority of the test cells, pointing to the potential importance of co-precipitation of calcium carbonate and SRP. Direct plant uptake, wetland filtering, microbial degradation, and co-precipitation with calcium carbonate were mechanisms thought to be responsible for P removal in these wetlands. Outflow TP concentration, an important measure for restoration performance, increased continuously with the increases in the TP mass loading rate at the north site, but peaked at approximately 30 µg L⁻¹ when the TP mass loading rate reached 0.5 g m⁻² yr⁻¹ at the south site.

Ground-water flow simulations were constructed to evaluate the interaction between ground water and wetlands systems, focusing on peatlands in the Kenai Peninsula Lowlands, south-central Alaska. Peatland systems occur in both recharge and discharge zones along transects simulated in computer models, whereas toe slope wetlands occurred in discharge zones. Sensitivity analysis indicates that hydraulic conductance of subsurface units has a strong influence on the rates and directions of ground-water flow exchanged between peatland systems and the surrounding mineral sediments, and needs to be further characterized to assess the hydrologic function of wetlands in the Kenai Lowlands. Perching of the water table was simulated in several modeling scenarios, altering ground-water flux rates to wetlands and shifting recharge zones to topographically lower areas. Runoff (saturated surface flow and shallow interflow) was the dominant flux in all simulations. Our exploratory simulations suggest three avenues for future research using computer modeling to evaluate wetland hydrologic function in the Kenai Peninsula: 1) improved simulation methods to better characterize ground-water perching and overland flow, 2) better characterization of the distribution and hydrogeologic parameters of geologic units, and 3) collection of hydraulic head data in and near representative wetland systems to calibrate computer simulations.

Over the past 200 years, an estimated 53% (about 47 million ha) of the original wetlands in the conterminous United States have been lost, mainly as a result of various human activities. Despite the importance of wetlands (particularly along the coast), and a longstanding federal policy framework meant to protect their integrity, the cumulative impact on these natural systems over large areas is poorly understood. We address this lack of research by mapping and conducting descriptive spatial analyses of federal wetland alteration permits (pursuant to section 404 of the Clean Water Act) across 85 watersheds in Florida and coastal Texas from 1991 to 2003. Results show that more than half of the permits issued in both states (60%) fell under the Nationwide permitting category. Permits issued in Texas were typically located outside of urban areas (78%) and outside 100-year floodplains (61%). More than half of permits issued in Florida were within urban areas (57%) and outside of 100-year floodplains (51%). The most affected wetlands types were estuarine in Texas (47%) and palustrine in Florida (55%). We expect that an additional outcome of this work will be an increased awareness of the cumulative depletion of wetlands and loss of ecological services in these urbanized areas, perhaps leading to increased conservation efforts.

Woodland seasonal pools in the northern Great Lakes region, limited in this study to northern Wisconsin and Michigan's Upper Peninsula, are potentially important sites for bat feeding and drinking. In order to determine the influence of pool size, hydroperiod, and structural complexity on relative bat activity, I surveyed pools (17 in 2004, eight in 2005 and 2006) at approximately two-week intervals throughout the summer, documenting bat species use with mist nets and AnaBat II echolocation recording systems. In 189 mist net-nights over three summers, I captured 114 individuals and identified 21,591 AnaBat call sequences. Little brown bats (Myotis lucifugus) dominated the captures (75.4%) and AnaBat call sequences (83.3%). Northern myotis (M. septentrionalis) were less common (19.3% of captures, 6.4% of identified call sequences) but ubiquitous across pools. Four additional species (Lasiurus borealis, L. cinereus, Eptesicus fuscus, and Lasionycteris noctivagans) were more commonly documented at larger pools. Across all years, relative bat activity (as estimated by call sequences per night) was significantly influenced by pool size (more activity at small and large pools than medium pools) and covaried with the proportion of water remaining in the pool. My study emphasizes the utility of pools of all sizes to bats, as larger-bodied bats preferentially use larger pools, while smaller-bodied Myotis spp. are capable of foraging at pools of all sizes. Relative activity of all species was secondarily driven by pool hydroperiod, as the number of bat call sequences per night decreased as the amount of open water declined.

Sediment deposition and storage are important functions of forested bottomlands, yet documentation and interpretation of sedimentation processes in these systems remain incomplete. Our study was located in the central Atchafalaya Basin, Louisiana, a distributary of the Mississippi River and contains the largest contiguously forested riparian wetland in North America, which suffers from high sedimentation in some areas and hypoxia in others. We established 20 floodplain transects reflecting the distribution of depositional environments within the central Basin and monitored general and local sediment deposition patterns over a three-year period (2000–2003). Deposition rate, sediment texture, bulk density, and loss on ignition (LOI, percent organic material) were determined near or just above artificial markers (clay pads) located at each station per transect. Transect mean sedimentation rates ranged from about 2 to 42 mm/yr, mean percent organic material ranged from about 7% to 28%, mean percent sand (> 63 µ) ranged from about 5% to 44%, and bulk density varied from about 0.4 to 1.3. The sites were categorized into five statistically different clusters based on sedimentation rate; most of these could be characterized by a suite of parameters that included hydroperiod, source(s) of sediment-laden water, hydraulic connectivity, flow stagnation, and local geomorphic setting along transect (levee versus backswamp), which lead to distinct spatial sedimentation patterns. Sites with low elevation (long hydroperiod), high hydraulic connectivity to multiple sources of sediment-laden water, and hydraulic damming (flow stagnation) featured the highest amounts of sediment trapping; the converse in any of these factors typically diminished sediment trapping. Based on aerial extent of clusters, the study area potentially traps 6,720,000 Mg of sediment annually, of which, 820,000 Mg represent organic materials. Thus, the Atchafalaya Basin plays a substantial role in lowland sediment (and associated contaminant) storage, including the sequestration of carbon. Findings on local sedimentation patterns may aid in management of flow to control sediment deposition and reduce hypoxia.

We quantified macroinvertebrate community characteristics in nine temporary or permanent wetlands, and related these to environmental conditions. Macroinvertebrates inhabiting the water column and shallow sediment (42-cm depth) were sampled 20 months after wetland construction in June 2005. A total of 29 taxa were collected, and macroinvertebrate communities varied among wetlands. Total macroinvertebrate biomass (mean ± SE  =  16.44 ± 4.72 g AFDW/m³) and densities (mean ± SE  =  372,096 ± 124,972 individuals/m³) were positively related to coarse particulate organic matter abundance (living and nonliving plant matter; CPOM) and negatively related to turbidity. Density of ecologically sensitive EOT (Ephemeroptera, Odonata, Trichoptera) taxa was also positively related to CPOM and negatively related to turbidity. Total taxa richness was negatively related to turbidity, and percent of total macroinvertebrate density consisting of EOT (% EOT) was positively related to CPOM. These relationships were greatly influenced by 10 dominant taxa (nematodes, physid snails, mites, small squaregill mayflies, narrowwinged damselflies, biting midges, non-biting midges, ostracods, cladocerans, and cyclopoid copepods) that were positively associated with CPOM and negatively related to turbidity. Two wetlands inhabited by common carp (Cyprinus carpio) appeared to be in the poorest condition. These wetlands had the lowest macroinvertebrate biomass and densities and highest turbidity. Additionally, although net uptake of total nitrogen (TN) occurred in these high-turbidity wetlands, NH₃ concentrations were two-fold higher in outflow than inflow. Net uptake of total phosphorus (TP) occurred only in wetlands with low turbidity, high CPOM abundance, and high macroinvertebrate abundance and diversity. To enhance macroinvertebrate abundance and diversity and ecological functions (e.g., nutrient removal) in newly constructed wetlands, management efforts should be directed toward increasing plant abundance and reducing turbidity.

Growth and nutrient responses of Rhynchospora tracyi (Tracy's beak-rush), a wet prairie species in the Florida Everglades, to redox intensity and phosphate availability were examined under controlled redox intensities (Eh: −150, 150, and 600 mV) and phosphate levels (P: 10, 80, and 500 µg P 1⁻¹) for 60 days. Root length, total biomass, and photosynthesis of R. tracyi were higher at Eh ₆₀₀ than at Eh₋₁₅₀. Growth variables (e.g., shoot length, biomass, relative growth rate, and root porosity) significantly increased with phosphate availability, while R. tracyi allocated more biomass to shoots and rhizomes than to roots at the higher P levels. Tissue P concentration increased 5–6 times when phosphate availability increased from 10 µg P l⁻¹ to 500 µg P l⁻¹, while P use efficiency and molar N:P ratio significantly decreased with P availability. Net P accumulation was significantly higher at P₅₀₀ than at P₁₀ across the three redox intensities. Tissue N concentration was significantly higher at Eh ₆₀₀ than at Eh₋₁₅₀, and higher at P₅₀₀ than at P₁₀. In terms of plant performance at the three redox intensities, we conclude that R. tracyi is not well-adapted to strongly reduced conditions that would result from lengthened hydroperiods. Altered hydroperiods may be a major reason why wet prairie species, such as R. tracyi, have decreased in abundance in some areas of the Everglades.

In Chlebowo mire (Wielkopolska region), we investigated testate amoebae in relation to 10 environmental parameters in the semi-natural floating vegetation of flooded peat workings. The measured parameters included: depth to water table (DWT), ground-water pH, color, conductivity, PO₄, NO₃, NH₄, SO₄, Ca, and Mg. Detrended correspondence analysis and canonical correspondence analysis (CCA) were used to analyze relations between the composition of testate amoebae communities and those variables. In canonical correspondence analysis, DWT, pH, and Mg remained after forward-selection as the main factors characterizing the changes in testate amoebae communities along the moisture and nutrient gradients. Characteristic species of testate amoebae for the various stages of floating-mat development in the flooded peat workings were distinguished. Communities of testate amoebae along with present-day vegetation reflect the process of progressive acidification, driven mainly by Sphagnum fallax. We consider this as secondary succession, since preliminary investigations of peat stratigraphy revealed sedge peat below no more than 5–40 cm of Sphagnum peat in undisturbed parts of the mire. This study increases our understanding of relationships between testate amoebae and their habitat, which is valuable for palaeoenvironmental studies. A local transfer function was developed with the use of six models: partial least squares, maximum likelihood, modern analogue technique, weighted averaging, tolerance down-weighted averaging, and weighted averaging-partial least squares. The weighted averaging model performed the best for depth to water table (root mean square error of prediction RMSEP  =  6.99) and pH (RMSEP  =  0.8). Results will be used as part of a regional training set to improve palaeoenvironmental reconstructions of Sphagnum peatlands.

The discharge of nutrient and ion-enriched agricultural and urban runoff into perimeter canals surrounding the Arthur R. Marshall Loxahatchee National Wildlife Refuge and subsequent intrusion into a natural soft-water marsh is causing ecosystem alterations. Because this habitat is among the last remaining rainfall-driven areas of the Florida Everglades, understanding the dynamics of canal water intrusion is important for marsh protection and restoration. Using conductivity sondes, we examined canal water movement in and out of the marsh along four transects based on 350 and 500 µS cm⁻¹ conductivity isopleths. Canal water intruded into the marsh to different extents, with the greatest intrusion observed on the west side of the refuge. Canal water was always evident in the marsh, and the maximum measured intrusion was 3.9 km from November 2004 through January 2006. Stage differences between the canal and marsh influenced the movement of water into and out of the marsh, with high inflow rates in the canal increasing intrusion into the marsh. Marsh areas with sediment elevations < 4.9 m were most sensitive to canal water movement. Our analyses will contribute to the understanding of hydrologic conditions that lead to pollutant intrusion into floodplain wetlands.

Nutritional, behavioral, and diet data for lesser scaup (Aythya affinis [Eyton, 1838]) indicates that there has been a decrease in amphipod (Gammarus lacustris [G. O. Sars, 1863] and Hyalella azteca [Saussure, 1858]) density and wetland quality throughout the upper-Midwest, USA. Accordingly, we estimated densities of Gammarus and Hyalella in six eco-physiographic regions of Iowa, Minnesota, and North Dakota; 356 randomly selected semipermanent and permanent wetlands were sampled during springs 2004 and 2005. We also examined indices of wetland quality (e.g., turbidity, fish communities, aquatic vegetation) among regions in a random subset of these wetlands (n  =  267). Gammarus and Hyalella were present in 19% and 54% of wetlands sampled, respectively. Gammarus and Hyalella densities in North Dakota were higher than those in Iowa and Minnesota. Although historical data are limited, our regional mean (1 to 12 m⁻³ ) amphipod densities (Gammarus Hyalella) were markedly lower than any of the historical density estimates. Fish, important predators of amphipods, occurred in 31%–45% of wetlands in North Dakota, 84% of wetlands in the Red River Valley, and 74%–84% of wetlands in Iowa and Minnesota. Turbidity in wetlands of Minnesota Morainal (4.0 NTU geometric mean) and Red River Valley (6.1 NTU) regions appeared low relative to that of the rest of the upper-Midwest (13.2–17.5 NTU). We conclude that observed estimates of amphipods, fish, and turbidity are consistent with low wetland quality, which has resulted in lower food availability for various wildlife species, especially lesser scaup, which use these wetlands in the upper-Midwest.

A population of wild boars (Sus scrofa) became established during the 1990s in the Natural Park of Aiguamolls de l'Empordà, a wetland on the western coast of the Mediterranean Sea (Catalonia, Spain). Between 2001 and 2004, a culling program was conducted to reduce the boar population. We collected and analyzed the contents of 142 stomachs to characterize boar diets, estimate impacts on ground-nesting birds, especially threatened species, and determine the relationships between boars and agricultural areas surrounding the park. The boar population consumed primarily plant material (94% by volume), particularly underground roots and rhizomes (33%). Agricultural (37%) and non-agricultural plants (49%) comprised very similar proportions of the diet. The primary foods were alkali bulrush (Scirpus maritimus) (24% by volume, and in 47% of the stomachs) and corn (Zea mais) (19% by volume and in 29% of the stomachs). Animal matter represented only 5.6% of the diet by volume, but occurred in 84% of the stomachs. The most important animal foods were, by volume, birds (2.3%) and crayfish (Procambarus clarkii) (1.7%) and, by frequency, snails (44%) and terrestrial arthropods (47%). Wild boar diets shifted seasonally between agricultural plants in summer and non-agricultural plants and acorns (Quercus sp.) in winter. Consumption of animal matter varied seasonally, crayfish were consumed primarily from May to October, terrestrial arthropods in May and June, and birds from March to April and September to October. Birds, especially ducks, were consumed most frequently while moulting, when vulnerable to predation. Given the high frequency of birds in the diet and the extensive rooting for underground parts of plants, the wild boar population might pose a threat to the coastal wetland ecosystem of the Natural Park of Aiguamolls de l'Empordà if allowed to become overabundant.

Florida apple snails (Pomacea paludosa Say) are prey for several wetland-dependent predators, most notably for the endangered Florida snail kite (Rostrhamus sociabilis Vieillot). Management concerns for kites have been raised regarding the impacts of wetland dry downs on snails, but little data exists to validate these concerns. We simulated drying events in experimental tanks, where we observed that snail survival patterns, regardless of hydrology, were driven by a post-reproductive die off. In contrast to earlier reports of little to no dry down tolerance, we found that 70% of pre-reproductive adult-sized snails survived a 12-week dry down. Smaller size classes of snails exhibited significantly lower survival rates (< 50% after eight weeks dry). Field surveys showed that 77% of egg production occurs in April–June. Our hydrologic analyses of six peninsular Florida wetlands showed that most dry downs overlapped a portion of the peak snail breeding season, and 70% of dry downs were ≤ 12 weeks in duration. Dry down timing can affect recruitment by truncating annual egg production and stranding juveniles. Dry down survival rates and seasonal patterns of egg cluster production helped define a range of hydrologic conditions that support robust apple snail populations, and illustrate why multiple characteristics of dry down events should be considered in developing target hydrologic regimes for wetland fauna.

Our study investigated the feasibility of using a constructed wetland for restoring a creek that had been seriously polluted by organic discharges from animal husbandry activities in the watershed. A fish-ladder type cascade was used to raise the average dissolved oxygen (DO) from 1.0 to 3.6 mg/L. The ecological treatment system removed 64.0% of suspended solids (SS), 43.0% of biochemical oxygen demand (BOD), and 11.0% of ammonia nitrogen. Additionally, reductions of BOD and nitrogenous biochemical oxygen demand (NBOD) were simulated using a first-order biokinetic model for biodegradation of organic matter. The monitored data fell within ranges of the model-based BOD and NBOD reductions, although NBOD reduction was over predicted. Hence, the first-order biokinetic model appears useful for estimating BOD and NBOD reductions in a constructed wetland.

Plant-based systems, such as wetlands and other ecological treatment systems, are promising, sustainable alternatives to conventional wastewater treatment. One of the biggest drawbacks of these systems when compared with conventional wastewater treatment systems is a large land area requirement; thus greater efficiency is needed to reduce land requirements and consequent costs. This research identified plant species that promote greater nitrogen removal, and whose use could lead to increased efficiency of ecological treatment systems. Potential nitrification and denitrification rates of bacteria associated with the roots of herbaceous species (Cyperus papyrus, Colocasia esculentus), and woody species (Hibiscus moscheutus and Salix nigra) were measured in the lab. Potential nitrification rates were determined from the rate of NO₃⁻ accumulation in microcosms containing wastewater and live plants. Potential denitrification was measured using the acetylene inhibition technique on microcosm incubations of filtered wastewater and plant roots. Significantly more NO₃⁻ (mg l⁻¹ hr⁻¹) was produced by bacteria associated with S. nigra and C. papyrus roots than in microcosms containing only wastewater, or H. moscheutus, (P < 0.001). Potential denitrification rates were significantly greater in H. moscheutos and S. nigra root microcosms than in C. esculentus and C. papyrus root microcosms on dry weight, wet weight and root area bases (P < 0.001). These results demonstrate that the efficiency of ecological treatment systems treating wastewater high in NH₄ would be improved with a mix of herbaceous and woody species, whereas wastewater high in NO₃⁻ would be most efficiently treated with woody species. Thus, a diversity of species is needed to optimize ecological treatment system function.

Infrequent inundations of river floodplains during the growing season are known to have a stronger impact on plant distributions than annual flooding in the winter and early spring. Growing season responses to flooding may be explained by 1) direct effects of flooding on fully developed plants, and/or 2) indirect effects on vegetation mediated by soil nutrient availability. Nutrient availability, in turn, is the result of the effects of summer flooding on the microbial community that reacts to changes in soil moisture conditions. We employed a mesocosm experiment to test these ideas. Soil monoliths were obtained from a highly modified floodplain on the river Rhine (Netherlands) and a more pristine floodplain on the river Narew (Poland). Vegetation performance and soil nutrient availability were measured in the monoliths, which were exposed to a 14-day summer inundation. Flooding had a negative effect on plant biomass in the Dutch soils, while biomass remained unchanged on soils from the pristine Polish floodplain. This is probably related to the absence of summer flooding in the Dutch floodplains due to intensive river regulation the last century. Summer flooding is still common in the Polish situation where more original hydrology patterns remained. One month after 14-day inundation there was a decrease in species diversity (Shannon's H) in both systems. This decrease was caused by better performance of a few graminoid species. Pore water phosphate concentrations were higher in Dutch soils and reached the highest levels during inundation. Nitrate concentrations were also generally higher in the Dutch mesocosms, although during inundation concentrations were very low in both soil types. Differences in nutrient availability between soils were reflected in aboveground biomass tissue concentrations, yet biomass response was apparently not related to nutrient availability. We conclude that ecological rehabilitation in the Netherlands, i.e., return to a more natural hydrology, resulting in an increased incidence of summer inundation could lead to a short-term reduction in productivity and changes in patterns of species abundance and dominance.

Peatlands are an important carbon (C) store but many have been drained and damaged by mechanical harvesting. Little is known about ecological processes on abandoned peatlands that have recolonized naturally nor the impact of plants on C balance of these sites. Over the course of 13 months, we measured amounts of litter falling from three different species colonizing an abandoned peat bog in north-eastern Scotland to calculate potential inputs of C and nitrogen (N). In parallel, a litter bag experiment quantified C loss from the litter of these species over 18 months. Calluna vulgaris produced the greatest amounts of litter (276 ± 32.3 g dwt m⁻² yr⁻¹); Eriophorum angustifolium produced 10.9 ± 2.6 g dwt m⁻² yr⁻¹ and Eriophorum vaginatum produced 42.3 ± 3.5 g dwt m⁻² yr⁻¹. Carbon loss varied from 30% (E. vaginatum) to 40% (Calluna) over 18 months, but differences among the three species were not significant. Overall, these findings indicate that Calluna can make significant inputs of C and N into degraded cut-over peatlands, but seasonal variation in inputs is considerable.