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Using a multi-scale experimental approach, the research undertaken in this thesis investigated the role of the flood pulse in ephemeral floodplain wetlands of the River Murray, in order to better understand the impact of river regulation (and permanent inundation) on these wetlands. An ecosystem-based experiment was conducted on the River Murray floodplain, to compare changes in nutrient availability and phytoplankton productivity in three ephemeral wetlands (over a drying/reflooding cycle) with three permanently inundated wetlands. In the ephemeral wetlands, both drying and re-flooding phases were associated with significant increases in nutrient availability and, in some cases, phytoplankton productivity. It was demonstrated that the ?flood pulse?, as described by the Flood Pulse Concept (FPC), can occur in ephemeral wetlands in dryland river-floodplain systems, although considerable variation in the nature of the pulse existed amongst these wetlands. Results of this experiment suggest that factors such as the degree of drying and length of isolation during the dry phase, the rate of re-filling, timing of re-flooding and the number of drying/re-flooding cycles may be potentially important in producing the variation observed. Permanent inundation of ephemeral wetlands effectively removed these periods of peak nutrient availability and phytoplankton productivity, resulting in continuously low levels (of nutrient availability and phytoplankton productivity). It was concluded that alteration of the natural hydrological cycle in this way can significantly reduce nutrient availability, primary production and secondary production, essentially changing the structure and function, the ecology, of these wetlands. Equally, the results of this experiment indicate that some of the changes resulting from river regulation and permanent inundation can be somewhat reversed, within a relatively short period of time, given re-instatement of a more natural hydrological regime. A mesocosm experiment was used to examine the influence of the dry phase, specifically the effect of the degree of wetland drying, on patterns of nutrient availability and primary productivity comprising the flood pulse. Compared to permanent inundation, re-flooding of completely desiccated sediments increased carbon (C) and nitrogen (N) availability while partial drying generally decreased, or had little effect on, C and N availability after re-flooding. However, degree of drying had little effect on phosphorus availability or rates of primary production measured after re-flooding, and it is possible that these two factors are related. Partial drying reduced rates of community respiration after reflooding, possibly a reflection of the reduced carbon concentrations measured in these mesocosms in this phase of the experiment. Degree of drying also influenced the macrophyte community (measured after three months of flooding), with plant biomass generally decreasing and species diversity increasing as the degree of drying increased (with the exception of complete sediment desiccation which had lasting negative effects on both macrophyte biomass and species diversity). The results of the ecosystem and mesocosm experiments were utilised, in addition to results collected from the same experiment conducted at two smaller scales (minicosms and microcosms), to assess whether the effects of hydrological regime on nutrient availability at the ?wetland? scale could be replicated in smaller-scale experiments. None of the smaller-scaled experiments included in this investigation were able to replicate the specific response to hydrological regime recorded at the ecosystem scale, however the mesocosm experiment did produce results that were more similar to those at the ecosystem scale than those produced by the mini and microcosm experiments. The results of this study indicated that extrapolation of results from small-scale experiments should be undertaken with caution, and confirmed that a multi-scale approach to ecological research is wise, where large-scale field experimentation and/or monitoring provides a check on the accuracy, and hence relevance, of conclusions reached via mesocosm experiments.

"October 2003" / Errata inside front cover. / Bibliography: p. 289-313. / iii, 334 p. : ill., map, photo (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis examines the influence of 'water regime', or spatial and temporal patterns in the presence of water, on the floristic composition of wetlands on the River Murray in South Australia. It explores the hypothesis that the composition of wetland vegetation is determined by components of the water regime, namely depth, duration and the rate and timing of flood and drawdown. / Thesis (Ph.D.)--University of Adelaide, Cooperative Research Centre for Freshwater Ecology and School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

Thesis (Ph.D.)--McMaster University, 2006. / Supervisor: Patricia Chow-Fraser. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 206-221).

<p>Two ecological models of nitrogen processes in treatment wetlands have been evaluated and compared. These models have been implemented, simulated, and visualized in the Modelica language. The differences and similarities between the Modelica modeling environment used in this thesis and other environments or tools for ecological modeling have been evaluated. The modeling tools evaluated are PowerSim, Simile, Stella, the MathModelica Model Editor, and WEST. </p><p>The evaluation and the analysis have been performed using McCall’s factors for software quality (McCall et al, 1977), a correlation analysis and the Constant Comparative Method (Glaser&Strauss, 1999). The results show that the modeling tools and the models can both be separated into two categories: Simple Components and Complex Components for the modeling tools, and Simple Models and Complex Models for the models. The major difference between the Simple Components and the Complex Components is the higher possibility of the Complex Components to create and reuse separate components and the higher complexity in these components. The similarities between the categories are that they are consistent, easy to overview and use, if no new components are to be created. The major difference between the Simple Models and the Complex models lies in the number of functions and in the possibility of reuse and expansion. The similarities between all the models are that they are all consequent, logical, valid, specialized, and easy to use if the user has programming skill. </p><p>To conclude thisthesis, the nitrogen decrease in a constructed treatment wetland can well be simulated using the Nitrification/Denitrification model expressed in Modelica and the MathModelica Model Editor. However, some changes to the Model Editor are recommended to make the creation of the model easier. The most important of these changes are the addition of a tutorial, the ddition of useful error handling and messages, and the removal of unnecessary Visio features.</p>

<p>Treatment wetlands been showed efficient for reducing pollutant in waste water. In Lajeado – RS, Brazil the landfill has poor leachate water treatment. It is necessary to supplement the treatment plant because they need to reduce BOD, COD and nitrate of the water going to recipient. A subsurface flow wetland (SSF) can be a good choice.  In order to be able to design an efficient SSF it is important to understand how the grain sizes of a substrate affect the reducing of pollutants in waste water. This study focus on two substrate, sand with grain size of 0 - 3 mm and gravel with the grain size of 10 - 20 mm. To see the grain size reduces BOD, COD and nitrate best, the experiment used eight pilot scales SSF for leachate water treatment, four filled with sand and four filled with gravel. Two different flows, four with batch and four used continuous flow; two of each was planted with <em>Thypa angustifolia</em> <em>L</em>. Samples were taken from each wetland every week during a four week period. The results showed that the wetlands with the fine- grained substrate; sand gave the better reduction of BOD, COD and TKN (total kjeldahl kväve). It also showed great reduction in color. Important to notice in this study is the lack of time; more samples are required to be able to establish a pattern.</p>

This study investigated the effect of plant surface area (plant density) on the efficiency of organic carbon removal in a bench-scale constructed wetland. Constructed wetlands are commonly assumed to be biofilm reactors in which organic carbon removal occurs primarily through sedimentation and aerobic degradation by attached microbial biofilms. In conventional biofilm reactors, aerobic degradation of organic carbon is proportional to the amount of surface area for microbial attachment, provided that sufficient oxygen is available. In contrast, current design equations for constructed wetlands assume that the amount of surface area is not an important parameter. A bench-scale simulation of a constructed wetland was conducted, using bulrushes planted at varying plant densities in soil with a free water surface depth of about 0.27 m. The carbon source was diluted ENSUR (TM). Total organic carbon (TOC) removal was measured. Concentration of TOC was correlated with biochemical oxygen demand (BOD). Tests were conducted in conditions of light and dark, and under two different carbon loadings. Performance of bulrushes was compared with that of inert acrylic rods. The rate of carbon removal by mature bulrushes was found to increase with increasing plant density until oxygen became depleted. Higher densities degraded carbon at rates much faster than those predicted by current design equations. Young bulrushes degraded carbon at faster rates than mature bulrushes. Once oxygen was depleted, rates of degradation were reduced to rates anticipated by current models. When plant density was 15% or greater, oxygen became depleted in less than 6 hours. Removal efficiency was greater at higher loadings (70 mg/l BOD) than at lower loadings (25 mg/l BOD). Bulrushes performed significantly better than inert rods, sometimes by a full order of magnitude. The microbial community on the bulrushes appeared to be more complex and robust than that on the rods. Also, the presence of light did not significantly increase degradation rates for the bulrushes but was significant for the rods. The microbial community on the rods contained a larger proportion of epiphytic algae. The presence of light did result is greater overall efficiency of removal for both bulrush and rods. Currently, a major drawback of constructed wetlands in wastewater treatment has been their demand for large areas of land. This study suggests that it would be possible to reduce the land area requirements for constructed wetlands for both carbon removal and nitrification/denitrification provided designs gave more consideration to oxygen supply. Using current designs, a retention time of 4-8 days typically results in 70% BOD removal. This experiment suggests that wetlands with a retention time of about 1 day could provide the same performance if additional oxygen were supplied. / Graduation date: 1995

The American alligator (Alligator mississippiensis) has been frequently studied in large reservoirs and coastal marshes. Large ontogenetic shifts in their diet and morphology have been linked with changes in habitat use, with adult males using deep, open water and juveniles and nesting females relying on vegetated marsh. In certain regions of the inland portion of the alligator’s range, these different aquatic habitats are represented by seasonal wetlands and riverine systems that are separated by a terrestrial matrix. Ontogenetic habitat shifts, therefore, would require overland movements between systems, which has important implications for conservation of the species. I tested several commonly used methods of surveying alligator populations to determine the most effective method of studying alligators in seasonal wetlands. I then used systematic trapping, nest surveys and radio telemetry to determine habitat use and overland movement rates by different sex and size classes. I found that seasonal wetlands provided nesting and nursery sites for these inland alligator populations, but that both juveniles undergoing an ontogenetic shift and nesting females move between the wetlands and riverine systems. Overland movements by alligators between the wetland and riverine habitats establish a level of functional connectivity between these aquatic ecosystems. I constructed a habitat suitability index of both the wetlands and the surrounding landscape to determine which patch and landscape characteristics were important to wetland use by alligators. I found that both descriptive wetland characteristics and the spatial relationships between wetlands were important predictors of alligator use. Overland movement was related to upland landuse as well as distance between aquatic habitats. Conserving a variety of wetland sizes and types within an intact upland matrix is critical to maintaining connectivity across the landscape. Furthermore, understanding how species may act as mobile links between ecosystems, particularly those with ontogenetic niche shifts, illustrates the importance of approaching conservation from a landscape perspective.

<p>The research was driven by a need to increase the knowledge base concerning wetland ecological responses, as well as to identify and evaluate the factors driving the functioning of the Franschhoek Trust Wetland. An ecohydrological study was undertaken in which vegetation cover, depth to groundwater, water and soil chemistry were monitored at 14 sites along three transects for a 12 month period. The parameters used include temperature, pH, electrical conductivity (EC), sodium, potassium, magnesium, calcium, iron, chloride, bicarbonate, sulphate, total nitrogen, ammonia, nitrate, nitrite and phosphorus. T-tests and Principal Component Analysis (PCA) were used to analyze trends and to express the relationship between abiotic factors and vegetation.</p>