M.A. / Wetlands are being lost and degraded in urban areas. Urban wetlands perform a diverse range of valuable functions. The loss of wetlands, therefore, has a negative impact upon urban human populations. One of the major threats to urban wetlands in Gauteng is the development of residential and commercial developments. As prime land for development is at a premium, the urban developer has targeted wetlands, which are canalised, drained or filled before being developed over. A typical example is that of the case study used for this thesis, where a wetland found in Johannesburg, Gauteng, is in the process of being destroyed, with the developers removing wetland vegetation, levelling the site and inhibiting the flow of the Wilgespruit River. Eventually a townhouse complex to be known as Wilgeheuwel Extension 29 is to be developed on the site. An integrated sustainable rehabilitation plan is required to ensure that the Wilgeheuwel Extension 29 wetland is rehabilitated. This plan is to take into consideration all the factors that influence the wetland negatively at present, including impacts upstream and possible future impacts. Therefore, a hierarchical approach is used, where management plans for the Wilgespruit River sub-catchment, the proposed development and the individual wetland are integrated into one plan.

The distinctive karstic, freshwater wetlands of the northern Caribbean and Central American region support the prolific growth of calcite-rich periphyton mats. Aside from the Everglades, very little research has been conducted in these karstic wetlands, which are increasingly threatened by eutrophication. This study sought to (i) test the hypothesis that water depth and periphyton total phosphorus (TP) content are both drivers of periphyton biomass in karstic wetland habitats in Belize, Mexico and Jamaica, (ii) provide a taxonomic inventory of the periphytic diatom species in these wetlands and (iii) examine the relationship between periphyton mat TP concentration and diatom assemblage at Everglades and Caribbean locations. Periphyton biomass, nutrient and diatom assemblage data were generated from periphyton mat samples collected from shallow, marl-based wetlands in Belize, Mexico and Jamaica. These data were compared to a larger dataset collected from comparable sites within Everglades National Park. A diatom taxonomic inventory was conducted on the Caribbean samples and a combination of ordination and weighted-averaging modeling techniques were used to compare relationships between periphyton TP concentration, periphyton biomass and diatom assemblage composition among the locations. Within the Everglades, periphyton biomass showed a negative correlation with water depth and mat TP, while periphyton mat percent organic content was positively correlated with these two variables. These patterns were also exhibited within the Belize, Mexico and Jamaica locations, suggesting that water depth and periphyton TP content are both drivers of periphyton biomass in karstic wetland systems within the northern Caribbean region. A total of 146 diatom species representing 39 genera were recorded from the three Caribbean locations, including a distinct core group of species that may be endemic to this habitat type. Weighted averaging models were produced that effectively predicted mat TP concentration from diatom assemblages for both Everglades (R2=0.56) and Caribbean (R2=0.85) locations. There were, however, significant differences among Everglades and Caribbean locations with respect to species TP optima and indicator species. This suggests that although diatoms are effective indicators of water quality in these wetlands, differences in species response to water quality changes can reduce the predictive power of these indices when applied across systems.

M.Tech. / South Africa is a water scarce country. The characteristic water pollution problems associated with both developing and developed economies are evident. Indicator organisms have been enumerated from samples collected from the Blesbok Spruit (Gauteng Province) over one year. Standard membrane filtration techniques were used followed by cultivation of E. coli and enterococcus on selective agars. Rainfall data was collected to enable a determination of differences, between “wet” and “dry” sampling runs. Descriptive statistics applied to the data include the calculation of the geometric mean for each sampling run and the geometric mean per sampling site in both wet and dry conditions. The Mann- Whitney Rank Sum Test and Kruskal-Wallis One way Analysis of Variance (ANOVA) were used to compare data sets. The capacity of the Blesbok Spruit, containing wetland areas, to assimilate the microbiological load was more effective than that of the Renoster Spruit (Free State Province) which does not contain distinctive wetland areas. The risk of infection has been determined by comparing the levels of E. coli and enterococcus to a set of site-specific guidelines. The water is not suitable for drinking or domestic purposes and full contact recreation will pose a risk of infection to users. The lower Blesbok Spruit has the poorest water quality and this water is unsuitable for livestock watering being only suitable for the irrigation of crops. The effects of diffuse pollution on the health related microbiological water quality need to be considered in the management of this sub-catchment.

This dissertation focused on developing an integrated surface – subsurface hydrologic simulation numerical model by programming and testing the coupling of the USGS MODFLOW-2005 Groundwater Flow Process (GWF) package (USGS, 2005) with the 2D surface water routing model: FLO-2D (O’Brien et al., 1993). The coupling included the necessary procedures to numerically integrate and verify both models as a single computational software system that will heretofore be referred to as WHIMFLO-2D (Wetlands Hydrology Integrated Model). An improved physical formulation of flow resistance through vegetation in shallow waters based on the concept of drag force was also implemented for the simulations of floodplains, while the use of the classical methods (e.g., Manning, Chezy, Darcy-Weisbach) to calculate flow resistance has been maintained for the canals and deeper waters. A preliminary demonstration exercise WHIMFLO-2D in an existing field site was developed for the Loxahatchee Impoundment Landscape Assessment (LILA), an 80 acre area, located at the Arthur R. Marshall Loxahatchee National Wild Life Refuge in Boynton Beach, Florida. After applying a number of simplifying assumptions, results have illustrated the ability of the model to simulate the hydrology of a wetland. In this illustrative case, a comparison between measured and simulated stages level showed an average error of 0.31% with a maximum error of 2.8%. Comparison of measured and simulated groundwater head levels showed an average error of 0.18% with a maximum of 2.9%.

The marsh rice rat (Oryzomys sp.) is a semiaquatic rodent native to wetlands in the southeastern United States. The northwestern-most part of the rice rat’s range extends to Illinois where rice rats are found in wetlands across the southern part of the state. Recent studies have shown that rice rats in the United States can be divided into two species: O. palustris and O. texensis, but the taxonomic status of rice rats in Southern Illinois is unclear. To resolve this, I sequenced cytochrome-b and the control region, two regions of mitochondrial DNA, for 16 rice rats and constructed a phylogeny using these new sequences and previously obtained O. palustris and O. texensis sequences. In contrast to previous morphological assessments, I found that rice rats in Southern Illinois should be classified as O. texensis. This would extend the range of O. texensis north and west from its current extent. Further investigation using nuclear loci will be needed to confirm this classification.

Soils contain nearly three times the amount of carbon (C) than the atmosphere, with C turnover times ranging from centuries to millennia. Although wetland soils represent a relatively small portion of the terrestrial landscape, they account for an estimated 20-30% of the global C reservoir. Seasonally flooded soils are likely the most vulnerable wetlands to climate change, as changing temperature and precipitation patterns are expected to alter the timing and duration of flooding. Seasonal variations in soil moisture are recognized as a critical control on soil C stocks and CO2emissions. However, the relative influence of associated changes in soil oxygen availability, root dynamics and the stability of mineral-organic associations are largely unknown. The overarching goal of this study was to examine the relative influence of redox state, root density and mineralogy on C cycling within seasonally flooded soil. To accomplish this goal, we combined seasonal monitoring of soil moisture, redox potential, and carbon dioxide emissions with a characterization of organic matter composition, mineralogy and root biomass along upland to lowland transects. We found that water saturation was the limiting factor for CO2emissions from seasonal flooded lowland soils, whereas soil temperature primarily regulated emissions from upland soils. Seasonal water saturation also resulted in topsoil C accumulation in lowlands compared to uplands, despite experiencing prolonged aerobic periods. Moreover, the C that accumulated in lowland topsoils was more chemically reduced compared to upland soils. However, the C chemistry in the subsoil showed the opposite trend of being more reduced in uplands compared to lowland subsoils. In sum, our results suggest that anaerobically protected soil C in seasonal flooded soils is particularly vulnerable to changing moisture regimes in response to climate change. To what extent this expected C loss is compensated by upland plant encroachment, or the neoformation of mineral-organic associations, warrants future research.

Up to 87% of the world’s wetlands have been destroyed, considerably reducing ecosystem services these wetlands once provided. More recently, many wetlands are being restored in an attempt to regain their ecosystem service. This study seeks to determine the effects of restored wetlands on local bat habitat use. Bat activity was found to be significantly higher around the wetlands when compared to distant grassy fields; however, no significant difference was found among the restored wetlands and a remote cattle farm containing multiple water features. Geospatial models of bat distribution and bat foraging were produced using machine learning that showed higher habitat suitability and foraging activity around restored wetlands than around distant grassy fields, suggesting that wetlands provide vital habitat for insectivorous bats. This study demonstrates that restored wetlands promote bat activity and bat foraging, and restoring wetlands may be a useful means of increasing natural pest control over nearby farmlands.

Intention for this study is driven by finding patterns that may be shown to reveal primary factors of influence for the abundance and diversity of wetland birds. These correlations may be used to promote wetland management strategies for the benefit of waterbird species, and help illuminate current local wetland conditions for waterbirds, respectively. The idea is to help enliven individuals to become a more conscious steward and manipulator of our environment through incorporating structural and biological components into wetland development and management strategies, and broadly speaking, urban development practices.

>Magister Scientiae - MSc / This work aimed at assessing the response of wetland vegetation productivity to the 2014-2017 climate-induced drought at the Soetendalsvlei wetland system in the Western Cape province of South Africa. To achieve this objective, firstly a literature review on the progress of remotely sensed data applications in assessing and monitoring wetland vegetation productivity was conducted. The review elaborates on the role of remote sensing in monitoring and assessing wetland vegetation productivity, with a detailed discussion of the climate change and variability impacts on wetland vegetation productivity. Accurate assessment results are produced when suitable processing techniques are selected as well as appropriate spatial and spectral resolution for extracting spectral information of wetland vegetation productivity. Secondly, wetland vegetation changes and productivity status was assessed using multi-temporal resolution Landsat series imagery and Normalized Difference Vegetation Index (NDVI) during the wet and dry seasons for the period between 2014 and 2018.

The 178,000-acre Grassland Ecological Area in California’s San Joaquin Valley is managed to provide overwintering habitat to waterfowl on the Pacific Flyway. The major management activity is the fall flooding and spring drawdown of wetlands, timed to optimize the availability of forage vegetation and invertebrates for ducks and shorebirds. Wetland drainage contains salt, boron, and trace elements that are, in part, derived from imported surface water but also concentrate during storage in the wetland impoundments. The spring drawdown drainage contributes to occasional water quality violations in the San Joaquin River (SJR) during dry years. Compliance with water quality objectives may be improved by delaying the traditional wetland drawdown period approximately one month to coincide with high SJR salt assimilative capacity during mid-March to mid- April when reservoir releases are increased to aid salmon migration. However, this delayed drawdown may affect the quality and quantity of wetland vegetative forage, increase wetland soil salinity, and possibly alter the concentrations of algae, invertebrates, and pollutants in the wetlands. In the research presented herein, initial data were collected on the effects of delayed drawdown on algae, invertebrates, and wetland water quality. The experimental sites chosen were three pairs of matched wetland basins (20-100 acres each) that are part of the larger Modified Hydrology Study being conducted in the Grassland Ecological Area. For each pair, one wetland was managed with a traditional March drawdown; while for the second wetland, drawdown was delayed approximately one month to coincide with the period of high SJR assimilative capacity. During the second year of the study, two drainage sites were sampled to characterize drainage flowing to the SJR from an aggregated wetland area. Soil and water column samples were collected during the flooded periods at the inlets, outlets, and along transects within the wetlands. Water quality analyses included total/volatile suspended solids, conductivity, nitrogen (NH4 +, NO2⁻+NO3⁻, organic), phosphorus (total, PO4 3-), organic carbon, alkalinity, turbidity, temperature, and pH. Planktonic and benthic invertebrates were identified and enumerated. Data were collected between February and April in 2007 and again in 2008. Identified phytoplankton were predominantly chlorophytes and diatoms. Zooplankton that feed on phytoplankton were found in abundance and consisted mostly of Cladocera. Benthic invertebrate densities were also measured to help explain the differences in algal concentrations between ponds. Benthic invertebrates were found to be predominantly Chironomidae. Seasonal loads of volatile suspended solids, total dissolved solids, and total organic carbon were estimated at the two aggregate drainage sites and at one delayed drawdown wetland during the 2008 season. For volatile suspended solids, the discharged load was 1500 lbs at the Buttonwillow drainage site, 2500 lbs at the Los Banos 38 drainage site, and upstream of those sites, 770 lbs were discharged from the Mud Slough 4b wetland. For total dissolved solids, the discharged load was 290 tons, 520 tons, and 26 tons, respectively, for the same locations. Of the factors potentially limiting phytoplankton concentrations, invertebrate grazing was likely the most important. Nutrients were not limiting in either the traditional or modified wetlands, as indicated by sufficient N and P content in the algae biomass. Likewise, inorganic C was not limiting, as indicated by pH (most <9.0 pH). Sunlight intensity was not significantly attenuated by water depth or turbidity, and thus light limitation was not indicated.