We estimated the global warming potential of Estonian peatlands (transitional fens and ombrotrophic bogs) based on greenhouse gases (GHG) CO₂, CH₄, and N₂O and carbon (C) accrual in biomass, and the effects of drainage on these processes. Data were derived from a review of the literature of boreal peatlands. Areal estimates of peatland types were multiplied with the values of the interquartile range of literature-derived GHG fluxes. The effect of drainage and radiative forcing of Estonian peatlands were also evaluated. Annual emission of CO₂, CH₄, and N₂O is estimated to be 278 to 1,056 × 10³ of CO₂ equivalent (eq), of which CO₂ makes up 22 to 44%, CH₄ 53 to 73%, and N₂O 3 to 5%. The annual efflux is 419 to 676 × 10³ CO₂ eq year⁻¹ from drained peatlands, and −141 to 380 × 10³ CO₂ eq year⁻¹ from the undrained peatlands. The annual loss of C from peatlands is estimated to be 38 to 86 tons C × 10³ year⁻¹. Thus due to drainage, Estonia's transitional fens and ombrotrophic bogs have gone from being sinks to sources of C.

Sulfate pollution of lakes and rivers is recognized as a serious problem in many regions of Central Europe, thus we evaluated the role of rewetted fens in mitigating sulfate pollution and tested if high sulfate concentrations in fen-feeding water counteract the re-establishment of their function as sinks for phosphorus (P). A long-term incubation experiment was conducted with highly decomposed peat from upper soil layers of fens that have been rewetted for 1 to 15 years. Periodic sulfate pulses to inundated peat mesocosms, equating to an annual loading of 50 g S m⁻², induced significant changes of sulfate consumption and phosphorus mobilization. Sulfate consumption of highly decomposed peat from all sampling sites was related to sulfate concentrations in overlying water (linear regression, p < 0.01). Sulfate additions also led to significant increases of P concentrations or P mobilization in peat porewater (t test, p < 0.05) and P concentrations in the overlying water were 2–3 times higher than in non-treated controls. In conclusion, rewetting of fens is an important tool to mitigate sulfate pollution of adjacent lakes and rivers. However, an elevated sulfate concentration in waters feeding the fen impairs P retention and increases P losses to adjacent surface waters.

The reduction of nutrients and sediments from agricultural runoff by natural wetlands has been commonly accepted, but their role in water quality improvement at the catchment scale has been seldom studied, especially in irrigated catchments. This study aims to elucidate the effect of natural and recently created wetlands on stream water quality after the conversion of a catchment for irrigation purposes. Water quality and morphometrical and vegetation-related variables were measured in 19 wetlands on a 750-ha agricultural catchment under semi-arid conditions in the Ebro basin (NE Spain). A pollution gradient was found, increasing from the wetlands located in the upper catchment to those in the lower catchment. Wetlands with the lowest degree of artificiality, measured as the amount of human created structures (e.g., channel excavation, dikes), and higher plant richness had the poorest water quality, probably because they were in the lower catchment and their water contained more pollutants carried from agricultural and saline soils upstream. Some of these wetlands also had the highest rates of sediment and N-NO₃ retention, in contrast to more artificial wetlands, which exported nutrients and sediments. Less artificial wetlands could also provide ancillary benefits such as biodiversity enhancement or landscape heterogeneity improvement.

The paper describes the removal of nitrogen in horizontal sub-surface flow constructed wetlands (HF CWs) for various types of wastewater. The survey includes more than 900 annual means from more than 300 systems in 36 countries that were categorized into municipal, industrial, agricultural, and landfill leachate. The results revealed that the highest average concentration of total nitrogen (TN) was found in landfill leachate (211 mg l⁻¹), while the highest average loading (3,080 g N m⁻² yr⁻¹) was recorded for systems treating wastewater from industrial operations. The average inflow TN concentration and loading for all systems were 63 mg l⁻¹ and 1,158 g N m⁻² yr⁻¹, respectively. For ammonia-N the results were similar — the highest average inflow concentration (162 mg l⁻¹) was recorded for landfill leachate and the highest average loading was recorded for agricultural wastewaters (2,722 g N m⁻² yr⁻¹). The results also indicated that there is a good relationship between inflow and outflow concentrations and loadings for both TN and NH₄-N. Harvesting aboveground biomass of emergent macrophytes in HF CWs removes only limited amount of nitrogen as compared to inflow load (commonly < 10%).

This paper summarizes water pollution problems in the Yangtze River Delta, China, caused by rapid economic growth and lack of wastewater treatment. Although precipitation and river runoff are abundant, surface waters in and around the delta are seriously polluted because of the dense population that contributes domestic sewage, and non-point source drainage from intensive agriculture, aquaculture, animal husbandry, and numerous small enterprises. On the other hand, the delta itself is a huge wetland with many artificial and natural wetlands, such as paddy fields, reed marsh, lakes, and rivers. How to make full use of these wetlands to improve the water quality in the Yangtze River Delta is an important challenge for wetland scientists. Potential solutions include establishment of constructed wetlands near outlets of sewage discharge tunnels, and developing floating mats on open water surfaces. Pilot experiments in the Yangtze Delta have shown improvements to water quality. In the meantime, clean industrial production lines, recycling water usage, and large scale application of water purification techniques should be implemented to mitigate the sources of water pollution.

Redox potential impacts wetland ecosystem functions and processes. This study assessed the temporal and spatial patterns and variability of soil redox potential in relation to: 1) hydrology, 2) soil phosphorus (P) enrichment, and 3) dominant vegetation community in an Everglades wetland. Probes installed for 2-week periods required 8 to 10 days for measurements to stabilize, considerably longer than what has been reported in the literature. Probes installed for 1 year yielded more stable measurements and were more useful for ecological analysis. Redox temporal patterns were related to water table fluctuation with redox increasing exponentially as the water table decreased from 5 cm above marsh surface. Large-scale spatial redox patterns were found in relation to P enrichment with higher average redox occurring in moderately-enriched regions (−134 mV) than in highly-enriched or unenriched regions (−185 mV for both). Vegetation community had no effect on redox status. Water level change was the primary driver of small-scale spatial variability (soil profile) with redox measurements varying more near the marsh surface during low water conditions. The degree of redox response to water table fluctuation decreased with increasing soil depth. These findings are important in understanding how altering hydrology can affect soil processes and ecosystem function.

We estimated the pre-settlement density and area of different classes of palustrine wetlands on the Des Moines Lobe based on soil characteristics. Six wetland classes, ranging from temporarily flooded to permanently flooded, were identified based on soil properties that persisted after artificial drainage. Prior to drainage, wetlands covered nearly half of the Des Moines Lobe and there were differences in both the types and relative abundance of wetlands among the four geologic subdivisions of the Lobe (Bemis, Altamont, and Algona till plains and Altamont Lake). In the flat Altamont Lake zone, the most common wetlands were equally split between temporarily flooded and saturated water regimes. Among the three till plain zones, saturated wetlands were the dominant wetland type. Differences in wetland distributions among the zones probably derive from differences in initial topography and post-glacial processes such as erosion-deposition processes and stream-network formation.

Soil organic matter (OM) is an important feature of natural wetlands (NWs) often lacking in created wetlands (CWs). Some have suggested that OM amendments be used to accelerate development of edaphic conditions in CWs. Our objective was to investigate microbial and geochemical responses to compost amendments at a CW. Five levels of amendments were incorporated into drier and wetter zones of the CW to test two hypotheses: 1) microbial biomass carbon (MBC) and denitrification potential will increase with increasing levels of amendments; and 2) phosphorus (P) sorption will decrease with increasing levels of amendments. Regression indicated that pH, MBC, and P sorption had linear relationships, while bulk density (BD) had an exponential relationship with amendment level. Denitrification enzyme assay (DEA) had highest values at intermediate amendment levels. Analysis of variance indicated amendment effects for BD, MBC, DEA, and P sorption, and wetness effects for pH and MBC. Amendment levels between 60–180 Mg ha⁻¹ were ideal for microbial development and denitrification, while not sacrificing P sorption, and would be more logistically and economically feasible than levels of 200–300 Mg ha⁻¹. However, responses to amendments were complex and optimizing amendments for certain functions may detrimentally affect other functions.

Wetland hydrology is an important factor controlling wetland function and extent, and should therefore be a vital part of any wetland mapping program. Broad-scale forested wetland hydrology has been difficult to study with conventional remote sensing methods. Airborne Light Detection and Ranging (LiDAR) is a new and rapidly developing technology. LiDAR data have mainly been used to derive information on elevation. However, the intensity (amplitude) of the signal has the potential to significantly improve the ability to remotely monitor inundation – an important component of wetland hydrology. A comparison between LiDAR intensity data collected during peak hydrologic expression and detailed in situ data from a series of forested wetlands on the eastern shore of Maryland demonstrate the strong potential of LiDAR intensity data for this application (> 96% overall accuracy). The relative ability of LiDAR intensity data for forest inundation mapping was compared with that of a false color near-infrared aerial photograph collected coincident with the LiDAR intensity (70% overall accuracy; currently the most commonly used method for wetland mapping) and a wetness index map derived from a digital elevation model. The potential of LiDAR intensity data is strong for addressing issues related to the regulatory status of wetlands and measuring the delivery of ecosystem services.

Salt marshes provide important ecosystem services, such as buffering the nutrient runoff from land to sea, and as nurseries for economically important fish species. Upland development in southern New England salt marshes has led to drastic increases in nitrogen runoff and associated changes in marsh diversity as Spartina alterniflora displaces high marsh species. How upland development impacts nitrogen levels and community parameters on northern New England salt marshes is not known. We assessed if upland development was associated with increased nitrogen and changes in plant community composition in a northern New England salt marsh. We found nitrate levels were higher in areas adjacent to development relative to those associated with intact upland, but that marsh nitrogen levels were generally much lower than those reported from southern New England. Areas associated with development had high Triglochin maritimum abundance but low S. alterniflora abundance relative to areas with no upland development. Correlations between nitrate and plant abundance corroborated these patterns. Our work suggests that in northern New England salt marshes, T. maritimum, rather than S. alterniflora, may be an early indicator of nitrogen runoff from upland development.

The Pantanal is the world's largest contiguous freshwater wetland spanning Brazil, Bolivia, and Paraguay. It contains the greatest wildlife densities in the Neotropics and was enlisted by all three countries in the Ramsar convention on wetland conservation. The Brazilian government, together the UNESCO's Man and the Biosphere Program, declared a biosphere reserve in the Pantanal in 2000. Other plans to protect the region include expansion of existing reserves and land use regulations following recommendations from the Cerrado-Pantanal priority setting workshop. Here we evaluated how four conservation scenarios complied with the principles of systematic conservation planning and analyzed their representativeness, efficiency, and complementarity using 17 vegetation classes as surrogates for regional biodiversity. We used MARXAN (systematic conservation planning software) to determine the value of the habitat types protected by each conservation scenario. We found that none of the four conservation scenarios met preferred areal targets for protection of habitats, nor did any protect all 17 biodiversity surrogates. The Pantanal Biosphere Reserve provided the best compromise in conservation planning.

To assess feasibility of reintroduction of extirpated spotted salamanders (Ambystoma maculatum) in restored flatwoods wetlands, hatching rates were monitored using pond enclosures. Ambystoma maculatum hatching success was compared to that of conspecifics in source ponds and to blue-spotted salamanders (Ambystoma laterale) that had persisted in restored ponds despite habitat degradation. Restored ephemeral ponds with hypoxic conditions had consistent hatching failure for A. maculatum. To isolate effects of dissolved oxygen (DO), laboratory gradients were used to identify levels of DO necessary for A. maculatum and A. laterale hatching success. DO treatments included 0, 2.0, 4.0, 5.0, 6.0, 7.0, and 8.0 mg/l for A. maculatum and 2.0, 4.0, and 6.0 mg/l for A. laterale. Ambystoma laterale hatched across all treatments. Ambystoma maculatum hatching was successful in treatments > 4.0 mg/l. Prescribed burns of dried ponds and selective girdling reduced leaf litter and increased in situ photosynthesis resulting in greater DO. Ambystoma laterale may have persisted in degraded ponds because of differences from A. maculatum in egg structure, and thus oxygen delivery. Land use changes contributing to hypoxia, including changes in forest composition and fire regime, may help explain the loss of A. maculatum from regional assemblages.

We tested wetland-restoration management techniques to restore and increase the diversity of aquatic beetle assemblages. Three wetland treatments were examined that included: (i) unplanted surface flow (unplanted SF) wetland, (ii) surface flow (planted SF) wetlands planted with aquatic plants, and (iii) subsurface flow (SSF) wetlands. Species richness of aquatic beetles in SF wetlands was highest in spring, while the abundance was lower in the planted SF wetlands than in the unplanted SF wetland. Planted SF wetlands had a slightly higher diversity of beetles than that of the unplanted SF wetland. The planted and unplanted SF wetlands had similar attributes throughout the rest of the year. In SSF wetlands, beetles were significantly more abundant and species rich in spring than either in the planted or in the unplanted SF wetlands. Beetle diversity in SSF wetlands was higher than that in SF wetlands. During the summer, the differences between treatments disappeared. Our results suggested that: (i) vegetation planting was a successful wetland restoration technique, due to the increased habitat diversity, (ii) subsurface flooding provided fishless temporary waters with favorable breeding conditions for aquatic beetles, thus it was also a useful restoration technique, and (iii) significant seasonal differences in abundance and species richness reflected the characteristic breeding habits of aquatic beetles.

In this study we were able to provide the first estimates of transition probabilities of wet prairie and slough vegetative communities in Water Conservation Area 3A (WCA3A) of the Florida Everglades and to identify the hydrologic variables that determine these transitions. These estimates can be used in management models aimed at restoring proportions of wet prairie and slough habitats to historical levels in the Everglades. To determine what was driving the transitions between wet prairie and slough communities we evaluated three hypotheses: seasonality, impoundment, and wet and dry year cycles using likelihood-based multistate models to determine the main driver of wet prairie conversion in WCA3A. The most parsimonious model included the effect of wet and dry year cycles on vegetative community conversions. Several ecologists have noted wet prairie conversion in southern WCA3A but these are the first estimates of transition probabilities among these community types. In addition, to being useful for management of the Everglades we believe that our framework can be used to address management questions in other ecosystems.

I tested the hypothesis that the quantity and quality of suspended and sediment organic matter in shallow coastal waters is affected by wind-induced resuspension at a smaller depth scale (< 1 m) than usually assumed. Water and sediment surface (0 to 1 cm) samples were collected on a seasonal basis and analyzed for total suspended matter, organic fraction, and phytopigments at 12 shallow sites representing a depth gradient from 0.2 to 2.0 m along the western shore of Sicily. Water column concentrations of all measured variables decreased rapidly with increasing water column depth, and concentrations levelled off at about 1 m water column depth. The likelihood of sediment resuspension by wind for various combinations of water column depth and fetch length was modelled using the CERC (U.S. Army Corps of Engineers, Coastal Engineering Centre, Washington D.C. US) model for 10 years of local wind data. The simulations indicated that even light winds (2 m s⁻¹) increased the likelihood of resuspension in the shallowest basin (0.2 m depth) with an effective fetch of 250 m. This study provides evidence that shallow water systems should not be investigated by considering the entire water column as a single homogenous layer. Investigations of shallow water ecosystems should consider 2 main layers with different ecological conditions and functions: a shallow surface turbulent layer from the surface to a depth of 1 m that is strongly affected by wind-driven physical forces and a deeper, below 1 m to the sediment surface, layer where wind-driven turbulence has less impact.

Riverine floodwater pulses provide water, nutrients, and sediments to floodplain wetlands, but flood pulses also act as a natural disturbance by removing biomass, scouring sediments, and delivering turbid waters. We investigated nearly pristine montane floodplain wetlands with varying degrees of river connectivity in Jasper National Park, Canada: three fully connected riverine marshes, three partially connected beaver-impounded marshes, and three completely disconnected railway-impounded marshes. Our objectives were to determine how river connectivity affects plant biomass and water and sediment chemistry, estimate impacts of nutrient limitations on plant biomass, and compare natural variations in river flooding on plant biomass and nutrients. The amplitude of water level fluctuations, a measure of flood disturbance and river connectivity, was highest in flood years and in riverine marshes. Sites with river connectivity had significantly higher plant biomass than sites without river connectivity (railway-impounded marshes). NO₃⁻-N, TP, and turbidity correlated positively with river floodwater pulses. A high flood year increased nutrient supply in the wetland water but significantly decreased plant biomass in all sites. Moderate flood disturbance and nutrient inputs from floodwaters provided optimal growing conditions for plants in these montane floodplain marshes.

Tangxunhu wetland is one of China's largest freshwater lakes and plays a significant role in the sustainable development of the city of Wuhan. Based on terrain maps, TM images, and statistical data from 1953 to 2005, the spatial characters and changing features of Tangxunhu wetland were quantitatively assessed by calculating the landscape metrics of shape index (SI), fractal dimension (D), and stability index (S). The results showed that Tangxunhu wetland had meandrous development over the past 53 years, with SI, D, and S decreasing from 1953 to 1967, increasing from 1967 to 2000, and then decreasing again from 2000 to 2005. SI, D, and S were lowest in 1967, indicating maximum instability, but highest in 2000, indicating maximum stability. These changes in Tangxunhu wetland were associated with various natural, social, and economic factors.