Investigations were made examining the relationships between gastropod species richness and abundance across 20 phosphate and 20 natural lakes in Central Florida. In additional to lake category, age of phosphate lakes was used to determine if phosphate lakes ever approximate natural lakes. Additional physical, chemical, and biological parameters, including chlorophyll a, Ca, secchi, phosphorous, conductance, fish predation, and recreational lake use were investigated in order to determine if they affected gastropods with lake age. Comparisons were also made between gastropod species richness and average abundance and two groups of dominant vegetation categories: Panicum, a structurally complex macrophyte, and Typha, a less structurally complex macrophyte. After phosphate mining operations are completed, Florida state regulations require the establishment of ecologically viable habitat (created lakes) which reflects the properties of regional natural lakes including vegetation structure, littoral zone, bank slope, and lake depth. The littoral zone is part of the mandated structure of the lake, and is of considerable importance to the uptake, storage, transformation and release of nutrients. Within the littoral zone, gastropods are a critical link in the food web with implications for the long term structure and function of a lake. They are known for their close associations with macrophytes and are common environmental indicators since they have limited mobility, high diversity, are well studied, are representative of their habitat type and have a widespread geographic range. They are also an important food sources for many predators in aquatic environments, include migratory waterfowl and game fish. Gastropod species richness and abundance data were collected via standard net sweep methodology. Abundance was presented in catch per unit effort, therefore all abundance data were averages. Initial comparisons between gastropod species richness and average abundance yielded no significant differences between natural and phosphate lakes. However, when age was applied as a covariate, there was a significant difference between lake age as a continuous variable in species richness comparisons. Additionally, categorical comparisons between lakes older or younger than 30 years indicated significantly higher species richness and average abundance of gastropods in lakes phosphate lakes older than 30 years. Physical and chemical properties of the lakes did not appear to influence gastropod populations between lakes of different ages. Fish predation interactions did not indicate any significant influence either. However, the presence of boat ramps did indicate a positive relationship between average gastropod abundance and species richness and recreational lake use. Littoral zone macrophyte comparisons between dominant vegetation Typha and Panicum indicated a significantly positive relationship between gastropod species richness and average abundance in older phosphate lakes dominated by the more structurally complex Panicum macrophytes. Confidence in the Typha and Panicum results was confounded by lack of access to younger, Typha dominated, phosphate lakes. An increase in sample size for younger Typha lakes, with additional site access, may further support these findings.

>Magister Scientiae - MSc / Drug-resistant infections are a global health crisis and drastically hinder the treatment options to effectively combat disease. Today, natural products remain an important source of novel drug candidates. Micro-organisms, in addition to being a source of bioactive natural products, represent a sustainable source of these compounds. As the marine environment is largely underexplored, the oceans represent a potential source of novel NPs. This study aimed at the discovery of novel NPs from bacteria associated with novel marine invertebrate species endemic to the South African coast, including a sponge Spongia (Spongia) sp. 001RSASPN and a tunicate, Pseudodistoma africanum Millar, 1954. The methodology comprised of culture-dependent and culture-independent strategies. The former involved the isolation of bacteria associated with the invertebrate species and subsequent screening for anti-microbial activity against a panel of indicator strains including a multi-drug resistant E. coli strain. Anti-bacterial activity was detected in 6.1% and 4% of bacterial isolates from the sponge and tunicate isolates respectively. The culture-independent strategy involved the use of PCR to select bioactive strains likely to contain novel NRPS or PKS secondary metabolite pathways. An NRPS A- domain exhibiting low sequence identity (65%) to reference sequences in the NCBI database was amplified from isolate PE8-15, a strain belonging to the genus Bacillus. This predicted a novel NRPS pathway within this strain. In addition, this isolate exhibited the most diverse anti-microbial profile including anti-bacterial and anti-fungal activity (A.fumigatus ATCC 46645). Therefore, as the most promising candidate, the genome of PE8-15 was sequenced following which 10 secondary metabolite pathways including bacteriocins (5), NRPS (3), siderophore (1) and a terpene pathway were identified. The A-domain amplified from PE8-15 originated from Cluster 4, and NRPS pathway predicted to encode a lipopeptide. Lipopeptides are an important class of compounds with a range of industrial applications in the pharmaceutical, cosmetic as well as food industry. The identification of potentially novel secondary metabolite pathways from even well- studied groups of organisms demonstrates the importance of sequence-based methods in natural product discovery. Furthermore, this study highlights the South African coast as a rich source of microbial natural products and should be exploited further for drug discovery.

Estuarine ecosystems are among the most biologically productive areas and they provide important ecosystem services such as erosion control, habitat and refugia for several species. These environments are characterized by the presence of a variety of organic matter sources due to their transitional position between rivers and the sea. The biotic compositions can undergo spatial and seasonal changes along the estuary due to the spatial and temporal fluctuations of environmental factors such as salinity, temperature and seston loads. Therefore, the different combinations of biotic and abiotic factors make each estuary a unique ecosystem. Because of this spatial and temporal complexity, the understanding of estuarine food web structure and which factors affect the trophic relationships within the ecosystem through space and time represent challenging tasks. Furthermore, estuaries are under an increasing number of anthropogenic perturbations because of the growing concentration of human populations in coastal areas. Knowledge of ecosystem structure and functioning is essential for effective conservation and management planning of coastal areas.In this dissertation, I combine the utilization of biological tracers to examine spatial and temporal variability in the food web structure within a small temperate and microtidal estuary located in South Africa. To this end, fatty acid profiles and stable isotope signatures were measured in several primary organic matter sources and consumers (including zooplankton, fishes and benthic invertebrates) during four consecutive seasons and in three different estuarine regions: upper, middle, and lower reaches. The three reaches had distinct habitat features of vegetation type and morphology, and in particular the lower reaches were colonized by the marsh grass Spartina maritima. Isotopic mixing models were used to estimate the relative contribution of each food source to the diets of invertebrates and fishes within the estuarine food web. The isotopic and fatty acid data showed similar results. In general, the lower reaches of the estuary were characterized by a higher deposition and assimilation by brachyuran crabs of carbon derived from marsh grass detritus, whiletowards the upper reaches a mixture of microphytobenthos and particulate organic matter (phytoplankton and detritus) was deposited and sustained the pelagic and benthic fauna. The highest deposition and assimilation of marsh grass detritus in the lower reaches of the estuary occurred during periods of low freshwater discharge (autumn and winter). In the upper reaches, microphytobenthos and suspended particulate organic matter were dominant basal food resources for the food web during all seasons. These results indicated that benthic consumers incorporated mainly local carbon sources from their local habitat.To clarify isotopic and fatty acid patterns I examined the trophic behaviour of the sesarmid crab Sesarma catenata through laboratory feeding experiments. Results from these experiments validated that decomposed leaves of riparian trees and the salt marsh plant S. maritima were the preferred food of the sesarmid crabs, potentially due to high bacterial loads. The remaining leaf material not assimilated by crabs, together with faecal material, are likely important subsidies for adjacent environments, hence representing an important energy pathway involving the microbial food chain. Furthermore, this dissertation showed the importance of mobile top predators as vectors energetically connecting distinct food chains within the estuary (i.e. littoral, benthic and pelagic). I concluded that a combination of physical (i.e. patterns of freshwater discharge and estuary morphology) and biological factors (i.e. organism feeding behaviour, mobility, primary productivity, the local vegetation type) influence the pattern of dominant primary organic matter sources, and therefore the food web structure along the estuarine environment. In particular, marsh grass detritus contributed substantially to the diets of estuarine fauna during periods of low freshwater discharge. Given the importance of the salt marsh habitat in providing trophic resources, it is important to preserve this environment to sustain the natural biota and ecosystem functioning.

Numerous ecological studies have used lipids to determine trophic pathways in aquatic systems, as fatty acid profiles provide time-integrated information on an organism’s assimilated diet. Many of these studies have, however, been based on sample collections with a limited temporal scale. The trophic ecology of pelagic systems has been studied intensively using fatty acid analyses, but very little work has been directed toward benthic communities, with the intertidal being especially neglected. The investigation of trophic pathways within rocky shore communities will help us to better understand system responses to environmental changes. The determination of long term temporal variation of the food web within a community could reveal the type, magnitude, duration and frequency of highly seasonal productivity. Changes in fatty acid profiles through time in primary consumers of intertidal rocky shores are poorly understood, but represent an important step towards a more comprehensive understanding of rocky shore food webs, compared with those derived from snapshot or short-term studies. The aim of this thesis was to clarify the temporal variability in the diets of rocky shore intertidal suspension-feeders (the brown mussels Perna perna and the Cape reef worm, Gunnarea gaimardi) and grazers (the Cape sea urchin Parencinus angulosus and the Goat-eye limpet, Cymbulus oculus) on the south east coast of South Africa using fatty acid profiles, and to investigate the effects of life style (e.g. feeding mode) and life cycle on temporal variations in tissue fatty acid profiles. I had three hypotheses: firstly, that suspension-feeders experience high levels of variability in their diets through time because water quality has the potential to change quickly and drastically, whereas grazers experience less variability in their diets over time since their food sources are more constant. Secondly, the reproductive cycles of the suspension-feeder P. perna and the grazer P. angulosus affect the fatty acid composition of their gonads, with temporal variations in lipid composition reflecting changes in reproduction investment. Thirdly, the total amount of energetic reserves available for reproduction are different for each gender (females allocate more energy to egg production than males allocate to gamete production). To address these aims, fatty acid profiles of suspension-feeders and grazers were investigated over a period of twelve months (from July 2010 to June 2011) at a single site on the south east coast of South Africa. The results showed high variability in the fatty acid composition of both the suspension-feeders strongly related with changes in their food source (suspended particulate material). Furthermore, similar temporal changes in fatty acid profiles of the two suspension-feeders were observed over time, reflecting their common diet and life style. There were some inter-specific differences in the suspension-feeders, likely originating from differences in their particle capturing mechanisms. Grazers showed less variability through time compared with the suspension-feeders, with the limpets being more consistent than the sea urchins. The temporal variability in the sea urchin diets may have resulted from the highly diverse and heterogeneous food sources available to them, whereas limpets may be more selective and have a limited range of diet items. Differences between the two grazer species may have arose from differences in their feeding strategies and intertidal zonation. The fatty acid compositions of gonad tissues in both P. perna and P. angulosus showed temporal variability strongly related to reproductive cycle. Differences in the fatty acid values between females and males were apparent, with females richer in total and polyunsaturated fatty acids than males. Spawning and gametogenesis influenced the variability of fatty acids through time in both species, suggesting the importance of considering the reproductive cycle when studying lipids in rocky shore species. Little evidence of lipid transfer between muscles and gonads was seen, suggesting the importance of direct lipid storage into the reproductive tissues. The influence of diet and life history of intertidal consumers on the temporal variability of their fatty acid compositions is important to understand, as it provides us with a better understanding of the functioning of rocky shore systems. There is an enormous potential for future research in this field of study.

This thesis presents an investigation of the 4-methoxypyrrolic constituents of two South African marine invertebrates, the nudibranch Tambja capensis and the bryozoan Bugula dentata. Three known compounds tambjamine A (7), tambjamine E (13) and the tetrapyrrole (15) were isolated during this investigation. All three compounds were shown to be active against oesophageal cancer in accordance with the general anticancer and immunosuppressive properties observed for 4-methoxypyrrolic natural products. Tambjamine A (7), tambjamine E (13) and the tetrapyrrole (15), together with tambjamine K (21) and L (22) (previously isolated in our laboratory) were used as standards to quantitatively assess the presence of these tambjamines in T. capensis and B. dentata collected from three different sites along the South African coast. This study confirmed that B. dentata is the source of the 4-methoxypyrrolic natural products sequestered by T. capensis and eliminated the closely related bryozoan B. neritina as a source of these metabolites. The paucity of tambjamine L (21) and K (22) obtained in previous investigations of the sequestered chemistry of T. capensis prompted an attempt at the development of synthetic methodology that could be used to synthesize tambjamines in sufficient yield for in depth bioactivity studies. In order to by pass the extensively reported problems associated with the synthesis of this group of compound 3-methoxy-2-formylpyrrole (47), readily accessible from 3-methoxypyridine N-oxide (48), was used as the starting material in a singlet oxygen induced 2,2’ bipyrrole coupling reaction. Although 47 proved unreactive in this coupling reaction, when the N-Boc protected analogue of 47 was used, and the reaction worked up in the dark, the novel methyl 4-aza-5-oxo-6,6-di-(2-pyrrolyl)-2(Z)-hexenoate (57) was obtained in low yield. The physical properties of tambjamine (E) (13) and the tetrapyrrole (15) were investigated to further the understanding of the proposed oxidative DNA cleavage mechanism and to determine the potential of the 4-methoxypyrrolic natural products as photodynamic therapy agents.

This thesis is divided into two parts and the rationale of the research conducted is based on the cytotoxicity of the prenylated quinones 1.24-1.29, isolated from the South African nudibranch Leminda millecra, against oesophageal cancer cells. The first part (Chapters 2 and 3) of the thesis initially documents the distribution of cytotoxic and antioxidant prenylated quinones and hydroquinones in the marine environment. We have been able to show, for the first time, that these compounds can be divided into eight structural classes closely related to their phyletic distribution. Secondly, we attempted to synthesize the two marine natural products 1.24 and 1.26 in an effort to contribute to an ongoing collaborative search with the Division of Medical Biochemistry at the University of Cape Town for new compounds with anti-oesophageal cancer activity. Accordingly, we followed the published synthetic procedure for 1.26 and, although we were unable to reproduce the reported results, we have generated five new prenylated quinone analogues 3.53-3.55, 3.63 and 3.71, which are a potentially viable addition to our ongoing structure-activity relationship (SAR) studies. Moreover, we embarked on a 7Li NMR mechanistic study for the synthesis of 3.2 from 3.1 which rewarded us with an improved and reproducible methodology for this crucial reaction that is detailed in Chapter 3. The second part of this thesis (Chapters 4 and 5) is concerned with a synthetic, structural, electrochemical and biological exploration of the 1,4-naphthoquinone nucleus as a primary pharmacophore in our search for new chemical entities which can induce apoptosis in oesophageal cancer cells, thus contributing to our overall ongoing SAR study in this class of compounds. Seven new naphthoquinone derivatves (4.19, 4.30, 4.31, 4.33 and 4.46-4.48) of the natural products 2-deoxylapachol (2.44), lapachol (4.1) and β-lapachone (5.2) were synthesized and 2-(1`-hydroxy-`-phenylmethyl)-1,4-naphthoquinone (4.29) was found to be the most cytotoxic (IC50 1.5 μM) against the oesophageal cancer cell line WHCO1, while 5.2, which is currently in phase II clinical trials as an anticancer drug, was found to be similarly active (IC50 1.6 μM). Electrochemical investigations of the redox properties of the benzylic alcohol derivatives 4.29-4.31 indicated a higher reduction potential compared to their oxidized counterparts 4.45-4.48, and this finding has been correlated to the increased activity of 4.29-4.31 against the WHCO1 cell line. Additionally, 4.29 is synthetically more accessible than either 1.26 or 5.2 and potentially a lead compound in our search for new and more effective chemotherapeutic agents against oesophageal cancer

Most invertebrate species are becoming extinct due to habitat loss and alien plant invasions. Hence this study aimed at determining the response of invertebrates to alien and indigenous vegetation within protected areas in the King Sabatha Dalindyebo (KSD) Local Municipality, Eastern Cape, South Africa. Invertebrates were collected using pitfall traps, during 12 sampling occasions from May 2010 to April 2011 numbers of sampling sites. Although the sampling method was adapted to collecting ground dwelling invertebrates, opportunistic flying invertebrates were also collected. A total of 7 flying invertebrate orders, 25 families, 34 species and 248 individuals were attracted to traps while 5 orders, 19 families, 50 species and 1976 individuals of soil surface-dwelling invertebrates were collected. ANOVA test showed no significant differences (p > 0.05) in species richness and abundance across sites for soil surface-dwelling invertebrates. Bray-Curtis similarity measures in PRIMER and correspondence analysis (CA) in CANOCO showed that sampling units with alien invasive plants shared most soil surface-dwelling invertebrate species at ± 75% level of similarity. Sampling unit A from the Mix alien (MA) site shared most species with indigenous vegetation sites. Sampling units from indigenous vegetation sites shared most species at ± 65% level of similarity. Multivariate analysis using CANOCO indicated that certain site variables such litter depth influenced the distribution of soil surface-dwelling invertebrates across sites. The study provided preliminary data and information for promoting invertebrate biodiversity conservation within protected areas (Nduli and Luchaba Nature Reserves) of the KSD Local Municipality. Key words: invertebrates, indigenous vegetation, alien vegetation, Lantana camara, Acacia mearnsii, and Eucalyptus.

In water depths of 500m to greater than 2,000m, off the West coast of Africa, sediments comprise very soft clays with extremely high water contents and plasticity. In situ CPT and T-bar testing in these areas have identified 'crusts' with undrained shear strengths of up to15kPa at 0.5m depth, before the strength reduces by an order of magnitude to normallyconsolidated strengths by 2m depth. This thesis presents an investigation into the behaviour and origin of these crusts. Mini ball-penetrometer tests on natural cores confirm the crustal strength, and indicate a sensitivity of 3 within the crust. However, pipeline interface tests using the Cam-shear device demonstrate a significant variability in the measured interface friction coefficient. Particularlylow strengths are observed when shearing in an undrained manner on a rough interface. These results are attributed to the heterogeneity of natural samples, and demonstrate the need to better understand the origin of the crust material in relation to interface micro-mechanics. A microbiological investigation of crust material by extracting bacteria DNA from claysamples is described, and identifies the presence of the bacterium, Marinobacter aquaeolei. This bacterium is then used to inoculate sterile samples to determine its ability to produce crustal strength. Through this work, it is concluded that M. aquaeolei is unable to create crustal strength, although extracelluar polysaccharides produced by this bacterium will influence thepermeability of sediments through the clogging of voids. It is therefore also concluded that future geotechnical investigation into marine sediments should consider the presence of bacteriaand their ability to influence the soil properties. Wet sieving of crust material shows that the crust comprises a mixture of burrowing invertebrate faecal pellets and clay. Pellets are found to represent 20% to over 55% of the crust material by dry mass. Individual pellets are shown to exhibit unconfined compressive strengths of between 5kPa and 50kPa, thus demonstrating their strength and robustness. Consolidationbehaviour is governed by the percentage of pellets in natural samples. Based ontheir location, abundance and strength, it is concluded that the origin of crustal strength lies with the presence of burrowing invertebrate faecal pellets. When sheared on rough pipeline interfaces, however, pellets are observed to crush, expelling void-filling fragments that may generatepositive excess pore pressures. Smeared clay produced when shearing natural samplesobstructs the dissipation of pore pressures, which may encourage hydroplaning, and explainthe observation of very low interface friction coefficients. It is therefore suggested that smooth pipelines offer more sliding resistance by minimising the risk of pellet crushing. This thesis proposes that wet sieving of core samples should be undertaken during the site investigationsfor future deep-water, hot-oil pipeline installations to provide design information on both the consolidation and strength behaviour of natural sediments.

Macroinvertebrates associated with the aquatic plant, water stargrass (Heteranthera dubia), were sampled from 12 waterbodies in four regions of the United States from June to August 2005. Taxa richness, evenness, and diversity were lowest in the Lower Midwest (LMW) region, and higher in Northern sites, especially the Upper Midwest (UMW), and Northeast (NE). While relative abundance varied from site to site and region to region, utilization of the plant by functional groups remained fairly constant. Collector-gatherers consistently comprised the largest portion of invertebrates sampled. The shredder/ herbivore functional group comprised an average of 17 % of total groups. Through an exhaustive literature review, it was found that shredder/ herbivores of water stargrass have not been reported in the literature. Because of this, the herbivore group was analyzed separately and consisted of 2,383 specimens representing 23 species. The most common groups were Rhopalosiphum sp., Nectopsyche spp. and chironomids. No differences were found in herbivore diversity or evenness between sampling regions, but species richness was significantly different.

The chemical fate and biological impacts of cyfluthrin in aquatic ecosystems were investigated using microcosms (1.9 m^3 concrete tanks) during 1989. Results were compared to a concurrent pesticide registration study using mesocosms (634.7 m^3 earthen ponds). Ten spray drift and five soil runoff simulations were conducted. Pesticide loadings were scaled by system volume, with the same experimental design in ponds and microcosms. Aqueous cyfluthrin concentrations and sediment residue values were generally higher in microcosms, while aqueous half-life was shorter in the smaller systems.