Impacted Wetlands Research Articles

The effect of inundation and salinity on the germination of seed banks from wetlands in South Australia

Three wetlands from the Upper South East of South Australia were chosen to investigate how a past history of drought (dry since 2002, 2004 and 2005) and salinity (2800 to >20,000 mg L −1) influenced the response of the seed bank to two water regimes (drained and flooded) and four salinities (500, 1000, 3000 and 5000 mg L −1). The maximum number of germinants (1270 ± 850 m −2) and species richness (7 ± 2.4) was greatest under the fresher drained treatment compared with the flooded more saline treatment under which there was no germination at one site. There were significant interactions between water regime and wetland previous history for two wetlands, but not the third which was the most saline and had experienced the longest drought. This indicated that the previous drought and salinity conditions experienced by a wetland affected seedling emergence but in the two less impacted wetlands the imposition of fresher drained conditions mitigated against these impacts. This suggests that if drought conditions continued with repeated exposure to elevated salinities the number of seeds and the species diversity of the seed banks would continue to decline.

Phosphorus Mass Balance and Internal Load in an Impacted Subtropical Isolated Wetland

Internal loading is a critical component of the phosphorus (P) budget of aquatic systems that can control trophic conditions. While diffusion across the soil–water interface is generally considered the dominant process controlling P load to the water column, advection due to water table fluctuations can also be significant. Our objective was to evaluate the role of diffusive and advective fluxes in relation to the total P (TP) loads entering and exiting an impacted wetland in the Lake Okeechobee drainage basin. The average diffusive flux of TP was 0.32 ± 0.14 mg m−2 day−1 and occurred for 240 days out of 314, while advective flux was 1.31 ± 4.03 mg m−2 day−1 and occurred for only 57 days. Phosphorus load to the wetland via internal modes was estimated to be 2.3 and 4.0 g day−1 from diffusion and advection respectively, accounting for 18% of the total P input, while overland flow (51%) was the major input pathway to the wetland. Ditch flow and groundwater outflow accounted for 49% (18.0 g day−1) and 14% (5.0 g day−1) of the total P output, respectively. This study shows the importance of advective flux in addition to diffusive flux and that the former should not be neglected when estimating internal P load of transiently flooded isolated wetlands. The monthly P budget-based retention and release patterns were consistent with previous findings, showing that intermittent flooding and drying cycling significantly reduces the P retention capacity of a wetland.

Elevation trends and shrink–swell response of wetland soils to flooding and drying

Given the potential for a projected acceleration in sea-level rise to impact wetland sustainability over the next century, a better understanding is needed of climate-related drivers that influence the processes controlling wetland elevation. Changes in local hydrology and groundwater conditions can cause short-term perturbations to marsh elevation trends through shrink–swell of marsh soils. To better understand the magnitude of these perturbations and their impacts on marsh elevation trends, we measured vertical accretion and elevation dynamics in microtidal marshes in Texas and Louisiana during and after the extreme drought conditions that existed there from 1998 to 2000. In a Louisiana marsh, elevation was controlled by subsurface hydrologic fluxes occurring below the root zone but above the 4 m depth (i.e., the base of the surface elevation table benchmark) that were related to regional drought and local meteorological conditions, with marsh elevation tracking water level variations closely. In Texas, a rapid decline in marsh elevation was related to severe drought conditions, which lowered local groundwater levels. Unfragmented marshes experienced smaller water level drawdowns and more rapid marsh elevation recovery than fragmented marshes. It appears that extended drawdowns lead to increased substrate consolidation making it less resilient to respond to future favorable conditions. Overall, changes in water storage lead to rapid and large short-term impacts on marsh elevation that are as much as five times greater than the long-term elevation trend, indicating the importance of long-term, high-resolution elevation data sets to understand the prolonged effects of water deficits on marsh elevation change.

Macroinvertebrate community structure and water quality variation in an effluent impacted wetlands (Lake Coleman), Victoria, Australia

Temporal and spatial variation in water quality and macroinvertebrate community structure were assessed in Lake Coleman, a shallow wetland adjacent to the Gippsland Lakes, Victoria, Australia. Littoral water quality and macroinvertebrate samples were collected annually in spring for 3 years following the cessation of a 30 year discharge of a treated effluent to the wetland. The discharged effluent contained highly coloured pulp and paper wastewaters as well as domestic and industrial effluents. Temporal changes in wetland water quality were related to the cessation of effluent discharge which resulted in reduced water colour and nutrient concentrations at discharge sites. Water quality was also affected by the inundation of the wetland by floodwaters in 1993 which lowered salinities across the wetland and also increased colour and nutrient concentrations at non-outfall sampling sites. Lake Coleman littoral macroinvertebrate species richness was lower than that reported for an adjacent, relatively unimpacted wetland, but was up to 3 times higher than in another local wetland impacted by sewage discharge. Macroinvertebrate community structure was variab;e over time and displayed no consistent pattern between sites. Changes in macroinvertebrates species richness and densities were associated with wetland flooding. Further monitoring is required to assess long term changes to wetland macroinvertebrate community structure resulting from current management strategies.

Characterizing deep soils from an impacted subtropical isolated wetland: implications for phosphorus storage

Soils within the Lake Okeechobee drainage basin, FL, USA, have been impacted by beef cattle and dairy operations and the landscape ditched and drained to facilitate stocking and grazing pastures. Restoring wetlands located on pastures has been proposed to reduce overland loss of phosphorus (P) by retaining it within the soils. However, soil properties of deeper horizons within impacted wetlands are rarely investigated due to the assumption that most dominant biogeochemical interactions occur at the soil–water interface. In this paper, we investigate soil properties up to 160 cm below the surface from an impacted isolated wetland and its surrounding upland pasture. Four intact soil cores were collected using the vibracoring technique, sectioned at 2-cm intervals, and analyzed for organic matter content by loss on ignition, total P by acid persulfate digestion, and water-soluble P using 0.01-M KCl solution. Bulk density and digital imaging were conducted using a multisensor core logger. Clay-sized phyllosilicates were identified using a computer-controlled X-ray diffractometer. Saturated hydraulic conductivity was measured using the slug-out technique, and the Hvorslev method was used to evaluate results. Unobliterated stratification was observed within the wetland in contrast to the pedologically formed A, E, and B horizons within the upland. The presence of clay horizons composed of smectite and kaolinite was dominant below 120 cm, posing potential hydrological and chemical implications, such as low conductivity and higher P sorption capacity. Saturated hydraulic conductivity of the soils was 1.22 m day−1 (±0.4). Diagnostic features such as increase in bulk density due to compaction, and the “red-edge effect” were useful in correlating the effect of cattle activity and hydrology on soil profiles. Soil organic matter content (38–48%) and total P (100–600 mg kg−1) concentrations were highest and well-correlated (r 2 = 0.81) at the surface. However, a significant amount of P was also present in the deeper horizons associated with clay. The deeper clay horizons account for up to 25% of P per hectare of the entire soil profile. These estimates are nontrivial and need to be accounted for while dealing with belowground P budgets, especially because subsurface lateral flows are dominant within the region.

Development of Indices to Predict Phosphorus Release from Wetland Soils

The U.S. Environmental Protection Agency created the Clean Water Action Plan to develop nutrient criteria for four water body types: lakes and reservoirs, rivers and streams, estuaries, and wetlands. Significant progress has been made in open water systems. However, only areas in and around the Florida Everglades have had numeric nutrient criteria set, due to the complexity, heterogeneity, and limited information available for wetlands. Our objective was to evaluate various soil tests to predict significant P release potential of soil in wetlands. A total of 630 surface soil samples (0-10 cm) were collected for this study from four southeastern states: Florida, Alabama, Georgia, and South Carolina. Soil samples were collected from the center of wetlands, the edge of the wetlands, and from adjacent uplands. The phosphorus saturation ratios (PSR), calculated using P, Fe, and Al molar concentrations from Mehlich 1 (M1-PSR), Mehlich 3 (M3-PSR), and oxalate (Ox-PSR) extractions and the amount of P extracted by different extractants were used to predict P loss potential from a soil. Total phosphorus (TP) concentration in wetland soils, estimated as the 75th percentile of the distribution of least impacted wetland soils as an example, was approximately 550 mg kg(-1). Based on this reference background condition, procedures for obtaining threshold values for P release to the surrounding water bodies were developed and threshold values calculated: M1-P = 24 mg kg(-1), M3-P = 44 mg kg(-1), Ox-PSR = 0.079, M1-PSR = 0.101, and M3-PSR = 0.067.

EFFECT OF SAND PARTICLE SIZE, OIL CONTAMINATION, AND WATER TABLE LEVEL ON THE EFFECTIVENESS OF SORBENTS IN WICKING OIL FROM CONTAMINATED WETLAND

ABSTRACT Oil spill cleanup in wetlands is problematic because of the limited remediation techniques that can be applied in such environments. The use of sorbents to clean up oil spills presents many advantages due to simplicity of approach and the inexpensive nature of these materials. Furthermore, sorbents can be used not only as wicking agents but also as microbial media that mediate hydrocarbon biodegradation. Once a sorbent is applied to an impacted wetland, it absorbs the contaminating oil. It retains the oil for a sufficient length of time to allow biodegradation of hydrocarbons by indigenous bacteria under aerobic conditions. In addition, plant-derived organic sorbents are biodegradable, thus leaving no permanent residue. Ammoniated bagasse is one of the biodegradable organic sorbents that contain nitrogen as a nutrient needed to support the activity of oil degrading bacteria. In this study, we evaluated the effectiveness of sorbents in wicking oil from the subsurface of oil-contaminated sediments under various conditions. Several microcosms were prepared to simulate saturated wetland environments. Glass cylinders, 10 cm in diameter and 10 cm in height, enclosed these microcosms. Each microcosm was layered in the following sequence (from the bottom to the top): a clean sand layer, an oiled-sand layer, and an overlying sorbent layer. Sand, sorbent, and water were sterilized prior to use to ensure that no biodegradation occurs during the experiment. The different conditions included: 2 particle sizes of sand (20 × 30 and 60 × 80 U.S. Mesh), 2 levels of oil contamination (25% and 75% of saturation), 3 water levels (at the oiled-layer/clean sand interface, at the oiled-layer/sorbent-layer interface, and at the sorbent-layer/air interface), and 2 levels of sorbent (presence or absence). Oil wicking experiments were performed in airtight microcosms for a period of 3 months. At the termination of an experiment, each layer of the microcosms was separated and samples were taken. Samples were extracted with dichloromethane and quantified by gas chromatography/mass spectrometry (GC-MS). Mass balances in each microcosm were established in terms of total petroleum hydrocarbons (TPH). TPH includes alkanes (C10-C35); pristane; phytane; hopane; 2-, 3-, and 4-ring PAHs; and pyrogenic PAHs (5- & 6-rings). The TPH change in each layer from time zero to 3 months was used to determine the effectiveness of the sorbent under each condition tested.

An assessment of wetland impacts and compensatory mitigation in the Cuyahoga River Watershed, Ohio, USA

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.

Fish community responses to ecosystem stressors in coastal estuarine wetlands: a functional basis for wetlands management and restoration

Functional responses of estuarine fish species to environmental perturbations such as wetland impoundment, changes in water quality, and sediment accretion are investigated. The study focuses on the feeding, growth and habitat use by California killifish (Fundulus parvipinnis), topsmelt (Antherinops affinis), and juvenile California halibut (Paralichthys californicus) in impacted coastal wetlands to provide an ecological basis for guidance on the management and restoration of these ecosystems. The ecology of California killifish, Fundulus parvipinnis, is closely tied with the marsh surface, which they access at high tide to feed and grow. Field estimates of food consumption show that killifish can increase their food intake by two-fold to five-fold by adding marsh surface foods to their diet. Bioenergetics modeling predicts that killifish can grow over an order of magnitude faster if they add intertidal marsh surfaces to their subtidal feeding areas. Tidal inlet closures and increased marsh surface elevations due to sediment accretion can restrict killifish access to the marsh surface, affecting its growth and fitness. An open tidal inlet and tidal creek networks that allow killifish to access the marsh at high tide must be incorporated into the restoration design. Topsmelt and California halibut are also adversely affected by tidal inlet closures. Food consumption rates of topsmelt are 50% lower when the tidal inlet is closed, compared to when the estuary is tidally-flushed. Tidal inlet closures inadvertently induce variations in water temperature and salinity and negatively affect growth of juvenile California halibut. Tidal creek networks which consist of channels and creeks of various orders are also important to halibut. Large halibut (>200 mm TL) inhabit deeper, high order channels for thermal refuge, while small halibut (<120 mm TL) are abundant in lower order channels where they can feed on small-sized prey which are typically less abundant in high order channels. Maintaining an open tidal inlet, implementing sediment management programs and designing coastal wetlands with tidal creek networks adjacent to intertidal salt marsh habitat (for fish access) are key elements that need to be considered during the planning and implementation of coastal wetland restoration projects.

Heavy metals in an impacted wetland system: A typical case from southwestern China

Historical zinc smelting in Hezhang, southwestern China, has resulted in significant heavy metal contamination of the surrounding ecosystems. The Caohai wetland system, which is an important national nature reserve close to the Hezhang zinc smelting area, was investigated in the present study. Results showed that sediments from the Caohai wetland system have been seriously contaminated by Cd, Pb and Zn with the highest concentrations in the surface sediments being up to 71, 160 and 1200 μg g − 1 , respectively. The heavy metals in the sediments were strongly associated with the organic/sulphide and residual fractions. A more oxidized condition induced by aquatic plants tended to cause the Cd, Pb and Zn bound to the Fe–Mn oxide fraction to become more dominant. Pb isotopic compositions in the sediments indicated that the inventories of Pb in the Caohai wetland sediments were mainly derived from the historical zinc smelting in the Hezhang area, although other anthropogenic sources, such as the gasoline Pb, also made a substantial contribution to the Pb in the sediments. Heavy metal contamination in aquatic plants was also studied and the results indicated that heavy metals accumulated by plants may pose a potential threat to the higher trophic-level organisms, including humans.

Pelobacter seleniigenes sp. nov., a selenate-respiring bacterium

Strain KM(T) is a novel bacterium with the unique metabolic abilities of being able to respire selenate as the electron acceptor using acetate as the carbon substrate and possessing the ability to grow fermentatively on short-chain organic acids such as lactate, citrate and pyruvate. Strain KM(T) was isolated from a sediment enrichment culture of a highly impacted wetland system in New Jersey, USA. Strain KM(T) is able to reduce selenate as well as selenite to elemental selenium. The unique metabolic capabilities of strain KM(T) include the respiration of nitrate, poorly crystalline Fe(III) and anthraquinone disulfonate. Phylogenetic analysis of the 16S rRNA gene of the novel isolate indicates that strain KM(T) groups within the family Geobacteraceae in the class Deltaproteobacteria with approximately 96-97 % 16S rRNA gene sequence similarity to the closest known organisms Malonomonas rubra Gra Mal 1(T), Pelobacter acidigallici Ma Gal 2(T) and species of the genus Desulfuromusa. Recognized species of the genera Malonomonas and Pelobacter cannot use any inorganic electron acceptors, while strains of the genus Desulfuromusa do not ferment organic substrates. This contrasts with the ability of strain KM(T) to ferment organic compounds as well as to couple selenate reduction to acetate utilization. Based on 16S rRNA gene phylogeny and metabolic properties, strain KM(T) represents a novel species for which the name Pelobacter seleniigenes sp. nov. (type strain KM(T)=DSM 18267(T)=ATCC BAA-1388(T)) is proposed. Based on the phylogenetic grouping of species of the genus Pelobacter within the Desulfuromusa cluster, it is suggested that Malonomonas rubra Gra Mal 1(T) should also be included in this group.

Testing the applicability of the SASS5 scoring procedure for assessing wetland health: a case study in the KwaZulu-Natal midlands, South Africa

A study was undertaken between 29th January and 17th February 2004 to test the applicability of the South African Scoring System Version 5 (SASS5) scoring and calculation procedure in nutrient-enriched palustrine wetlands in the midlands of KwaZulu-Natal, South Africa. Four reference wetlands and three dairy-effluent impacted wetlands were sampled. Six macroinvertebrate samples were collected with a SASS net from each wetland. For each sample, the macroinvertebrates were identified and assigned a predetermined SASS5 tolerance score. Data for selected physico-chemical variables, macrohabitat condition, biotope suitability and organism detectability were collected to assist in interpretation of results. Thirty-eight taxa, identified to family level, were collected during sampling. Total SASS5 scores ranged from 15 to 82. Five of the wetlands had mean SASS5 scores of between 46 and 59. Five of the wetlands had an intra-wetland SASS5 score range of greater than 30. Average score per taxa (ASPT) values ranged from 3.3 to 5.5, and few high scoring (≥ 8) taxa were collected. There was no significant difference in SASS5 scores between samples collected above, at, and downstream of, an effluent discharge point within the same impacted wetland. SASS5 scores for reference wetlands were also not significantly higher than those recorded for impacted wetlands. Comparison of ranked SASS5 scores and environmental data did suggest a relationship between the variables, but this was not significant. Based on the SASS5 score water quality guidelines, all sampled wetlands were considered to have impacted water quality. However, this was not supported by the macrohabitat and physico-chemical results. There are a number of possible reasons for the low SASS5 scores: the lack of biotopes present in wetlands compared to rivers (most notably the absence of the stones-in-current biotope), lower levels of dissolved oxygen present compared to rivers, limited habitat availability due to low rainfall during the sampling season, and the limited detectability of organisms due to large amounts of substrate in the samples. Without modification, SASS5 appears unsuitable for assessing wetlands. However, variation in taxon composition — within impacted wetlands and between reference and impacted wetlands, revealed through multivariate analysis — suggests that macroinvertebrates are responsive to changes in wetland condition, and thus show potential as indicators of wetland water quality. It is recommended that a habitat or biotope index be further developed and used in conjunction with any future wetland macroinvertebrate bioassessment protocols.

EVAPOTRANSPIRATION DYNAMICS AT AN ECOHYDROLOGICAL RESTORATION SITE: AN ENERGY BALANCE AND REMOTE SENSING APPROACH1

ABSTRACT: Little work is reported where spatial methods are employed to monitor evapotranspiration (ET) changes as a result of vegetation and wetland restoration. A remote sensing approach with the Surface Energy Balance Algorithm for Land (SEBAL) for estimating ET at The Nature Conservancy's Glacial Ridge prairie‐wetland restoration site in northwestern Minnesota is presented. The calibrated 24‐hour ET from SEBAL was estimated with an average error of prediction of −4.3 percent. Monthly, interseasonal, and seasonal ET for the period of June to September (2000 to 2003) from three adjacent land‐uses: a hydrologic control preserved wetland; a treated or restored site; and a nontreated or impacted wetland, were used in the study. Results from comparing ET behavior to the preserve suggest restoration efforts have affected monthly and seasonal ET within the treated site. Spatial average standard deviations of the seasonal ET within the preserve, treated, and nontreated sites give 47.3, 75.7, and 109.9 mm, respectively, suggesting hydrologic stabilization within the treated site. Monthly and interseasonal comparisons show similar behavior to that of the seasonal data, where monthly correlations suggest increasing agreement within the treated site, approaching those within the preserve.

Development and use of the Wetland Fish Index to assess the quality of coastal wetlands in the Laurentian Great Lakes

We use fish and environmental data from 40 wetlands of the Laurentian Great Lakes to develop the Wetland Fish Index (WFI), a tool that can be used to assess the quality of coastal marshes. A partial canonical correspondence analysis was used to ordinate fish species along multidimensional environmental axes that accounted for anthropogenic disturbance based on temperature, conductivity, and the presence of pollutants (e.g., suspended solids and primary nutrients). Compared with other measures of fish habitat quality (e.g., Shannon–Wiener diversity index and species richness), the WFI was the only index that was significantly related to the degree of water quality degradation and wetlands condition, as indicated by an independent index of wetland quality, the Water Quality Index (WQI). WQI ranks sites according to deterioration in water quality and is statistically related to the degree of land-use alteration in wetland watersheds. We demonstrate the usefulness of the WFI for detecting intrawetland variation between two sites in a degraded urban wetland, Frenchman's Bay, Lake Ontario, and to distinguish the heavily impacted wetlands in lower Green Bay from the less-impacted marshes in middle and upper Green Bay, Lake Michigan. This was accomplished by using only published fish data without corresponding environmental variables.

Biological Assessment of Slope Wetlands on the Coastal Plain of South Carolina

ABSTRACT Slope wetlands occur where groundwater emerges from hillsides to create shallow pools. These wetlands may be the initial point of contact between biota and emerging contaminated groundwater. We sampled several slope wetlands on the upper coastal plain of South Carolina that received contaminated groundwater and compared them to undisturbed slope wetlands. All of the wetlands supported a variety of insects, especially midge larvae and other Diptera, annelid worms, and aquatic beetles. Some supported large numbers of mites and copepods, and a few supported salamanders. Most taxa were tolerant of harsh conditions such as low dissolved oxygen and pH. Assemblage composition varied among wetlands due to differences in hydroperiod and likelihood of being flooded by nearby streams. Also important was the lack of shading in some disturbed wetlands, which permitted the growth of filamentous algae, sphagnum moss, and other plants. Few metrics commonly used for impact assessment differed between disturbed and undisturbed wetlands. High natural variability among slope wetlands and the natural tolerance of many slope wetland organisms may complicate the development of slope wetland multimetric indices, although such indices may be useful for identifying severely impacted wetlands.

Hydrology or Floristics? Mapping and Classification of Wetlands in Victoria, Australia, and Implications for Conservation Planning

A national approach to the conservation of biodiversity in Australia's freshwater ecosystems is a high priority. This requires a consistent and comprehensive system for the classification, inventory, and assessment of wetland ecosystems. This paper, using the State of Victoria as a case study, compares two classification systems that are commonly utilized to delineate and map wetlands--one based on hydrology (Victorian Wetland Database [VWD]) and one based on indigenous vegetation types and other natural features (Ecological Vegetation Classes [EVC]). We evaluated the extent of EVC mapping of wetlands relative to the VWD classification system using a number of datasets within a geographical information system. There were significant differences in the coverage of extant EVCs across bioregions, different-sized wetlands, and VWD wetland types. Resultant depletion levels were markedly different when examined using the two systems, with depletion levels, and therefore perceived conservation status, of EVCs being significantly higher. Although there is little doubt that many wetland ecosystems in Victoria are in fact threatened, the extent of this threat cannot accurately be determined by relying on the EVC mapping as it currently stands. The study highlighted the significant impact wetland classification methods have in determining the conservation status of freshwater ecosystems.

Impacts of stressors on the emergence and growth of wetland plant species in Pennsylvania, USA

Agriculture and urbanization in the upland landscape often generate stressors, such as sedimentation and eutrophication, that may negatively impact wetland plant communities. Individual plant species responses to stressors are also likely influenced by the hydrologic and geomorphologic characteristics of different wetland hydrogeomorphic (HGM) subclasses. The goal of this study was to determine to what extent the two stressors listed above influence the growth and development of wetland plant species and how these responses vary across HGM subclasses. The impacts of the two stressors on wetland plant species emergence and growth were examined in a 2 × 2 factorial greenhouse experiment, using soil moisture and organic matter content to simulate three HGM subclasses. Both stressors elicited significant responses in species establishment and growth, but overall trends in stressor responses differed by wetland type. For instance, sedimentation reduced the emergence of four species in simulated riparian depressions but only affected one species in simulated slope wetlands and none in simulated headwater floodplains. Sedimentation had little impact on any species establishment or growth in headwater floodplains. Approximately half of the species showed an increase in at least one growth variable in response to nitrogen enrichment. Additionally, the conditions used to simulate HGM subclasses appeared to impact a species performance and sensitivity to stressors. Therefore, further investigation of the impacts of HGM subclass conditions on species performance is needed. We expected differences in species responses to be related to their natural distribution across pristine and impacted wetlands; however, no obvious relationships were found. Our results suggest that it will be difficult to make generalizations about species responses to stressors because responses varied by stressor type, stressor interactions, and HGM subclass. Therefore, perhaps the next step in formulating broad generalizations and predictions about wetland plant community composition will require a shift from species-based approaches to a trait-based approach for examining how species composition may change in response to future disturbances.

Sediment chemistry: a history of mine contaminant remediation and an assessment of processes and pollution potential

The chronological geochemical record contained within sediments has been used worldwide to describe the history of contamination. Sediment analysis has proven invaluable in ascertaining the source of pollution, the processes leading to pollutant attenuation and the potential downstream impacts through remobilisation of toxicants. This study investigates the sediment chemistry of a natural wetland within the mining region of the Zambian Copperbelt. The research is based on recent cores from the impacted wetland and a nearby control site, and uses sediment and pore-water metal chemistry, sediment dating and diffusive flux estimations in determining (i) the source of contamination, (ii) the processes leading to pollutant accumulation and (iii) the potential risk the system poses to the downstream ecosystem through pollutant remobilisation. The study identifies effluent from a nearby mine as the most likely source of wetland contamination and provides evidence for the remediation of metal-laden effluent within the wetland through the accumulation of 150 tons of Cu and 100 tons of Co. Precipitation (Fe, Al and Cu) and adsorption (Co, Ni and Zn) of metals onto suspended solid surfaces, and their subsequent settling within the wetland are identified as primary processes leading to metal accumulation within the sediment. The sediment is shown to be a potentially important source of pollutants, with downstream pollution possibly continuing for 80–120 years post cessation of effluent discharge. In considering the further use of natural wetlands for mine effluent remediation, a complexity of factors such as the processes involved in remediation (e.g. precipitations vs. adsorption), the impact on the system (e.g. sediment metal accumulation), the remediative capacity of the wetland (e.g. metal loading) and the potential threat to downstream ecosystem should be considered, and contrasted with the potential benefits of downstream ecosystem protection through effluent attenuation within the natural system.

Use of in Situ Burning at a Diesel Spill in Wetlands and Salt Flats, Northern Utah, U.S.A: Remediation Operations and 1.5 Years of Post-Burn Monitoring

ABSTRACT On 21 January 2000, a release of an estimated 100 barrels of diesel was reported from a product transportation pipeline north of Great Salt Lake in Utah. During the next few days, due to weather related conditions (freeze/thaw periods and wind), the product spread over 38 acres of salt flat and wetlands. Initial oil containment efforts were successful in reducing the risk of oil impacts to natural resources in a nearby national migratory bird refuge, but the risk remained to migratory waterfowl that were expected to arrive at the impacted wetland within approximately 6 weeks. As a result, in situ burning was proposed to remove the free-phase diesel and destroy the hydrocarbon-impacted vegetation. Upon approval of a Site Remediation Plan and Fire Management Plan, a Heli-Torch was used on 10 March, 2000 to burn the most-highly impacted 12.8 acres. The following month (late-April), 3.2 acres of remaining lightly oiled vegetation were burned using drip torches and propane wands. It was estimated that 75–80% of the spilled diesel was burned in these operations. Because burning of the free-phase hydrocarbons and impacted vegetation would not remove product that had penetrated into the soils, bioremediation techniques were subsequently implemented, in order to further reduce hydrocarbon levels in the soil and attain the regulatory cleanup level of 20 mg/kg total polycyclic aromatic hydrocarbons.

Workers Safety &amp; Health During Iguassu Oil Spill Response Oil Spill in Iguassu River – Araucaria, Parana, Brazil

ABSTRACT On July 16, 2000 a major oil spill occurred at the side of the Araucaria refinery. A total of 4,000 m3 of a light crude oil run down around two kilometers trough Saldanha creek, crossing and contaminating four wetlands. The oil discharged into Barigüi River, a tributary of Iguassu River contaminating 6 kilometers in Barigüi River and 60 in Iguassu River. An oil recovery and cleanup operation was mounted. Almost 3000 workers were hired in haste to clean and recover oil in the impacted wetlands area, as well as in the water streams. The accident happened on a Sunday afternoon, during one of the coldest (for Brazilian standards) winters in past years, with temperatures as low as − 6°C. At the start of the oil recovery work, a very important issue was worker's safety and health. Most of the workers were unskilled people, unemployed until the accident and among them a great number of illiterate persons. The paper describes the issues with regards to safety and health, the actions taken to protect worker's health during manual oil recovery in wetlands, the means used to reduce hydrocarbon vapor exposure and evaluation of worker's exposure to hydrocarbon vapors. The effort was successful, in nine days all the free oil was removed from the rivers. The cleaning of the riverbanks and inundation areas was completed in three months. The creek and wetland areas ascending Barigüi River held around 70 per cent of the spilled oil. In these areas the safety and health concerns where higher. All superficial oil was removed from the rivers and streams.