Assessing the impacts of Lantana camara and opportunities for ecological restoration after its removal: does clearing facilitate both soil and native vegetation recovery?
- Authors: Bolosha, Uviwe
- Date: 2024-10-11
- Subjects: Lantana camara , Restoration and conservation , Restoration ecology , Invasive plants , Physicochemical process , Soil seed banks , Invasion driver
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466524 , vital:76738 , DOI https://doi.org/10.21504/10962/466524
- Description: Invasive alien plants (IAPs) are one of the major contributing factors to biodiversity loss, and Lantana camara is among the top ten alien invaders worldwide. Lantana camara threatens native biodiversity and human health, prevents natural succession, and has an economic and environmental impact globally. With current climate change and future predictions, these IAPs are anticipated to continue posing huge threats to ecosystem composition, structure, and function. Even though L. camara is a widespread IAP, there is still limited knowledge in South Africa on how it influences soil physicochemical properties at the species level, vegetation communities, and soil seed banks at the community level following its invasion. There is also minimal knowledge on the management and control (i.e., clearing for restoration purposes) of L. camara in South Africa, especially in the Eastern Cape province of South Africa. To address the knowledge gap, this thesis was structured into three main aspects: understanding L. camara invasion mechanisms, evaluating invasion impacts on both the aboveground and belowground communities, and invasion management. The main objectives of this thesis were (i) to examine how L. camara invasion (at a species level) affected soil physicochemical properties across different seasons, (ii) to assess how L. camara influences natural vegetation (at a community level), (iii) to examine the effects of L. camara invasion (at the community level) on belowground soil seed banks and also assess the availability of pioneer native species and IAPs in the soil seed banks, and (iv) to evaluate soil and vegetation responses following L. camara clearing in comparison to invaded and uninvaded conditions. To answer these objectives, different studies were carried out in the Eastern Cape province, South Africa, on various farms within the Albany Thicket Biome. The results (Chapter 3) show that L. camara alters and modifies some soil physical properties, such as soil infiltration rate, repellency, and soil penetration resistance, in the communities it invades. A significant decrease in soil penetration under the L. camara canopy was observed compared to soils from the edge and out position. Moreover, significantly faster infiltration rates were observed in the canopy and edge positions than in the out position. The study also observed that these modifications in soil physical properties vary depending on the season. A seasonal comparison in soil penetration showed that soil was more compact in the dry season than the wet season, and significantly faster infiltration rates were observed in summer than in the other seasons. The soil collected under the invaded sampling positions was mostly wettable (80–100%), and not strongly, severely, or extremely repellent across all the seasons. The changes in soil properties caused by L. camara could create favourable conditions for its growth and invasion. Seasonal changes in soil properties also highlight how environmental conditions, especially temperature and rainfall patterns, can affect soil physical properties. The findings in Chapter 4 observed both the negative and positive impacts of L. camara, where the species did not have negative effects on species richness, diversity, or cover of some native species growth forms (i.e., graminoids and forbs). For all species, both species richness and Shannon-Wiener (H’) were significantly higher in the L. camara invaded condition compared to the uninvaded condition. The Simpson’s (J’) and Pielou’s evenness (D’) indices, however, showed no differences between the invasion conditions. Furthermore, the effects of L. camara on vegetation cover were growth form-dependent, with differences being noted for trees and shrubs but not for graminoids and forbs. Changes in vegetation structure and composition were also noted where L. camara created favourable conditions for some species to co-occur with it, meaning that its known trait of changing soil physicochemical properties could benefit some species. Generally, the results of this study showed that the effects of L. camara on vegetation are varied and do not have a predictable pattern, so they should not be generalised. The findings (Chapter 5) also indicate that the L. camara invasion had a negative impact on seedling abundance and composition but not species diversity and richness. This is evident through the decrease in seedling abundance of forbs and graminoids in the L. camara invaded condition. Lantana camara also acted as a refuge for some plant species, mostly native forbs and grasses, including Aptenia cordifolia, Chamaesyce prostrata, Oxalis spp., and Setaria spp., as well as alien forbs such as Bidens pilosa, Plantago lanceolata, and Taraxacum officinale, suggesting L. camara does not entirely eliminate less competitive plant species but can co-exist with them. Lantana camara also displaced some native species, and this could be associated with their displacement in the standing vegetation. Moreover, the species also displaced the seed banks of some alien species, thus showing its competitive ability. Overall, L. camara invasion negatively influenced soil seed bank seedling abundance and composition of some species, but not diversity and richness. The results in Chapter 6 indicated that clearing L. camara is an effective method for reducing its population. However, our findings suggest that clearing alone may not be enough to re-establish these communities with native species. This is because the results of this study showed varied changes in soil properties and native vegetation (species richness, species diversity, percentage cover, and composition) after L. camara clearing. For example, soil moisture and soil penetration resistance showed no significant differences among the invasion conditions; only monthly variations were observed. This is an indication that seasonality influenced these properties. Significantly lower soil infiltration rates were observed in the cleared condition compared to the other conditions and were influenced by the months and the interaction of the clearing conditions and months. The water droplet penetration time showed no significant difference among the clearing conditions over the three months, and all the soil collected from the three clearing conditions was mostly wettable. Soil chemical properties showed that the L. camara invaded and cleared conditions had significantly lower soil pH compared to the uninvaded condition, and an increase in soil pH was observed after clearing L. camara. Vegetation characteristics showed that both the Shannon-Wiener index (H') and the Simpson’s index (D') were lower in the invaded and cleared conditions compared to the uninvaded condition, and significant differences were observed. A slight increase in the H' and D' indices was also observed after clearing L. camara. The mean percentage cover for trees and shrubs was significantly higher in the invaded condition than in the cleared and uninvaded conditions. However, the mean percentage cover of forbs and graminoids was similar among the invaded, cleared, and uninvaded conditions, and no significant differences were observed. When L. camara was cleared, native species recovery was observed and was more notable in the understory species. Overall, some signs of vegetation recovery were observed, although challenges such as secondary invaders and re-invasion by L. camara were noted in the cleared areas. This chapter then concluded that active restoration interventions should be incorporated during restoration to fast-track soil and vegetation recovery. The findings of this thesis will make several significant contributions to the field of biological invasions and provide baseline information that can be used in future studies. These are discussed in the various research chapters. Overall, the thesis concludes that L. camara invasion has varied impacts on native vegetation and soil, and its clearance, should be prioritised to reduce the negative impacts. However, L. camara cleared areas (by WfW in South Africa) require follow-up and monitoring at an early stage to assess vegetation and soil restoration success. In addition, active management measures after L. camara’s removal should be considered for clearing programmes to yield positive ecosystem recovery. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2024
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- Date Issued: 2024-10-11
Investigation into methods of recovering campylobacter spp. from river water samples
- Authors: Ngoni, Nandipha
- Date: 2023-10-13
- Subjects: Campylobacter jejuni , Stream chemistry , Organic water pollutants South Africa Eastern Cape , Water quality Measurement , Turbidity , Physicochemical process
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424177 , vital:72130
- Description: Campylobacter species are slender, gram-negative, rod-shaped, spiral- or curved-shaped with single or pairs of flagella. They are the leading cause of diarrheal disease globally, consumption of and contact with water contaminated by faeces is a major risk factor for transmission of these organisms to humans. Rivers used for recreation and domestic and agricultural activities represent all the risk factors for Campylobacter spp. pollution and human exposure. Campylobacter spp. However, effective methods to recover Campylobacter spp. from river water samples are lacking, indicating the need for the development of more efficient methods of detection and isolation of these organisms from environmental water samples. Campylobacter detection in a water sample is critical to ascertain potential risks to humans. The aim of this study was to determine a suitable method for the detection of Campylobacter spp. from river water samples and the objectives were to (i) to evaluate the performance of different methods used for the recovery of Campylobacter spp. from environmental water samples based on Campylobacter colony count and PCR identification results, (ii) isolate and enumerate Campylobacter cells from river water samples, and (iii) identify Campylobacter spp. in river water samples. The Bloukrans River was chosen for this study because it is suspected to be contaminated by faecal inputs from nearby informal settlements without adequate sanitation, as well as untreated/insufficiently treated effluents from nearby wastewater treatment plants. First, the physicochemical quality of the river water and the presence of faecal contamination were assessed to confirm suitability for Campylobacter spp. survival and presence. Then different approaches to sample, concentrate and recover Campylobacter spp. from river water samples were assessed. The different methods assessed were (i) direct enrichment of water samples without prior concentration, (ii) prior concentration of water samples by centrifugation followed by membrane filtration of supernatant, and after that, pooling the residue and pellet together for enrichment, (iii) sampling by the Moore Swab technique. For all three methods, enrichment in Bolton broth supplemented with Bolton antibiotics was conducted. This was followed by plating on modified cefoperazone charcoal deoxycholate agar (mCCDA) and incubation under a microaerophilic atmosphere at 42°C for 48 h. Colony morphology, Gram staining and polymerase chain reaction (PCR) were used to identify and characterize the microorganisms. The growth of blue colonies on the mFc agar surface confirmed presence and faecal pollution of the Bloukrans River. The physicochemical properties, based on the range of pH measured at different sites of the river (between acidic 3.45 to 6.42 and alkaline 7.2 to 8.74) indicate that Campylobacter spp. can thrive in the river. Based on the results from enumeration and sequencing of colonies recovered by each method, it was discovered that the most suitable method to recover Campylobacter spp. from river water samples is by prior centrifugation (14,000 × g for 30 minutes) followed by membrane filtration of the supernatant, and subsequent pooling of the residue and pellet. The pooled residue and pellet might have increased Campylobacter spp. concentrations aiding more growth during the enrichment of Campylobacter spp. from the river water samples. Results from enumerating Campylobacter spp. cells from river water samples indicate that Campylobacter spp. are present in Bloukrans River. The sequence obtained from the PCR product indicates that the species found were Campylobacter jejuni (96% homology as evaluated by BLAST). This study provided a procedure effective for obtaining a satisfactory quantitative recovery of Campylobacter spp. from environmental waters, a critical need for quantitative microbial risk assessment studies. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
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- Date Issued: 2023-10-13
Phytoplankton and aquatic macroinvertebrate assemblages from coastal and inland lakes of South Africa
- Authors: Nkibi, Esethu
- Date: 2023-10-13
- Subjects: Aquatic biodiversity South Africa , Indicators (Biology) , Lakes South Africa , Physicochemical process , Salinity , Phytoplankton , Aquatic macroinvertebrates
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424435 , vital:72153
- Description: Freshwater lakes are generally defined as permanent natural standing water bodies, with some of them having a direct and indirect connection with groundwater, rivers, and the ocean. Freshwater lakes provide essential socio-economic and ecological goods and services including recreation, aesthetic, support aquatic biodiversity, food in a form of fisheries and water for domestic use. Given their critical role in sustainability in providing socio-economic services, freshwater lakes are among the most threatened ecosystems globally due to intense human impacts over the last decades. South Africa has limited freshwater lakes, which according to the National Biodiversity Assessment (NBA 2018), we know little about their current biology except historic aquatic biodiversity studies conducted in the early 1940s. There are no management strategies in place to protect and conserve freshwater lake biodiversity and important ecosystem services. This thesis aims to: (1) produce a biodiversity inventory of phytoplankton and aquatic macroinvertebrate species and, (2) investigate important environmental drivers responsible for phytoplankton and aquatic macroinvertebrate species composition from six South African freshwater lakes. It was hypothesized that the three lake types will show different phytoplankton and aquatic macroinvertebrates species composition attributed by the geographical region (coastal and inland lake) and related physico-chemical parameters. Study sites consisted of two Northern KwaZulu-Natal coastal lakes (hereafter Coastal Lakes, CL) i.e., Lake Sibaya, Lake Mzingazi; two fresh inland lakes (hereafter Fresh Inland Lakes, FIL) i.e., Lake Banagher fresh and Lake Tevrede Se Pan; and two inland salt lakes (hereafter Salt Inland Lakes, SIL) i.e., Lake Banagher salt and Lake Chrissiesmeer, all inland lakes are situated in Mpumalanga province, together with other Pans making up the Mpumalanga Lake District of South Africa. The study sites were categorized based on their geographical position i.e., coastal vs inland and physico-chemical characteristics i.e., the presence and absence of aquatic vegetation, dominate substrate, salinity and different physico-chemical concentration i.e., Temperature, Dissolved Oxygen. Aquatic macroinvertebrates were collected from four littoral zone sites (< 1-meter depth) around each lake, whereas phytoplankton samples were collected from four water column sites (> 5-meters depth) and (0.5-meter depth) from the water surface at each lake during summer and winter season. The results were consistent with our hypothesis that both phytoplankton and aquatic macroinvertebrate species composition were influenced by physico-chemical parameters and that the differences in salinity concentration and aquatic vegetation between CL, FIL, and SIL were the driving factors for phytoplankton and aquatic macroinvertebrate species composition. In summary, one hundred and twenty-two phytoplankton taxa were collected and identified during this study, belonging to seven Phyla which included Chlorophyta, Bacillariophyta, Cyanophyta, Chrysophyta, Dinophyta, Euglenophyta, and Cryptophyta. The most abundant phytoplankton groups were Bacillariophyta and Chlorophyta. Phytoplankton relative taxa abundance, Pielou’s evenness, taxa richness, and Shannon diversity were significantly different between lake types. Aquatic macroinvertebrates, on the other hand, summed up to 10 orders, 67 families, and 80 taxa. The most abundant group were the order Coleoptera, Hemiptera, Odonata, and Gastropoda. Aquatic macroinvertebrate relative taxa abundance, taxa richness, and Shannon diversity were also significantly different between lake types. Aquatic macroinvertebrate relative taxa abundance, Pielous evenness, and Shannon diversity index were not significant between seasons, and only taxa richness was significant. Canonical analysis of principal coordinates (CAP) results further showed unique and distinct phytoplankton and aquatic macroinvertebrates community composition between lake types. The present study provides baseline biodiversity inventory (or species list) for important lake ecosystems biological indicators i.e., phytoplankton and aquatic macroinvertebrates and species composition in relation to lake type for six freshwater lakes in South Africa. Furthermore, the study provides empirical evidence that will inform policy and the development of management strategies for freshwater lakes in South Africa which is currently missing. The current study will also contribute to the next National Biodiversity Assessment Report (2024), concerning the freshwater lakes biological data deficiency noted in the previous NBA (2018) report. The study will also fill up the gaps to better understand species composition in lake systems and how they function which is currently limited. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2023
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- Date Issued: 2023-10-13
Assessment of the microbial quality of various domestic rainwater harvesting systems and the suitability of a nano based treatment method
- Authors: Malema, Mokaba Shirley
- Date: 2020
- Subjects: Escherichia coli , Water harvesting , Microbial contamination , Water Purification , Physicochemical process
- Language: English
- Type: thesis , text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/110218 , vital:33249 , https://dx.doi.org/10.21504/10962/110218
- Description: Thesis (PhD)--Rhodes University, Faculty of Science, Chemistry, 2020. , In most developing countries, people from rural and peri-urban settlements depend on harvested rainwater (HRW) as an alternative water source for drinking and other household purposes. Despite this reliance, there is little monitoring of the microbial quality of HRW in these areas. The most important issue in relation to using untreated harvested rainwater for drinking and other domestic purposes is the potential public health risks associated with microbial pathogens. Unlike chemical contamination, microbial contamination my lead to disease occurring rapidly, hence the need for frequent monitoring. Thus, the current study investigated the microbial quality of various domestic rainwater harvesting systems and the suitability of a nano based treatment method. The first experiments involved determining the microbial (Escherichia coli) and physicochemical quality (pH, turbidity, nitrate and chemical oxygen demand (COD)) of HRW in the Eastern Cape Province, South Africa. Samples were collected from 11 tanks situated at the Rhodes University, Kenton-on-sea (coastal) and in homes in the Grahamstown area on a weekly basis between June and September 2016. The Colilert-18®/Quanti-tray® 2000 system was used for enumeration of E. coli while physicochemical parameters were measured using commercial kits. Results showed that all samples were contaminated with varying concentrations of E. coli ranging from 7 to 1055 MPN/100 mL. Physicochemical analysis revealed that pH ranged from 5.6 to 7.6 and Turbidity values obtained for all tanks were below 5 NTU except for tank 4 (5.12 ± 4.96 NTU) and 7 (5.58 ± 8.19 NTU). Nitrate levels (range: 5.95 to 28.12 mg L-1) and COD (range: 66.53 to 191.12 mg L-1) were higher than the recommended South African drinking water quality guidelines in most of the tanks. In the second experiments, the objective was to determine whether a modified hydrogen sulphide (H2S) test kit with an improved detection rate is an effective preliminary screening qualitative test that can be used for rainwater quality monitoring. The hydrogen sulphide method is a low-cost microbiological field-based test which can be used in areas where water testing facilities are limited. Harvested rainwater samples were collected from various tanks in the Eastern Cape and tested for contaminants of faecal origin using the modified hydrogen sulphide test kit, Colilert-18/Quanti-tray®/2000 and membrane filtration technique. Faecal coliforms were measured using membrane filtration, E. coli was measured using Colilert and correspondence rates were calculated with results of the improved hydrogen sulphide test kit. E. coli results ranged from <1 – >2419.6 MPN/100 mL while the faecal coliforms ranged from 0 – >300 CFU/mL. The agreement rate with hydrogen sulphide test and membrane filtration was 88% while the agreement rate for the Colilert and hydrogen sulphide test was 76%. The third experiments investigated the prevalence of pathogenic E. coli strains and their antimicrobial resistance patterns in HRW tanks in the Eastern Cape, South Africa. E. coli isolates obtained in the first experiments were further screened for their virulence potentials using polymerase chain reaction (PCR) and subsequently tested for antibiotic resistance using the disc-diffusion method against 11 antibiotics. The pathotype most detected was the neonatal meningitis E. coli (NMEC) (ibeA 28%) while pathotype enteroaggregative E. coli (EAEC) was not detected. The highest resistance of the E. coli isolates was observed against Cephalothin (76%). All tested pathotypes were susceptible to Gentamicin, and 52% demonstrated multiple-antibiotic resistance (MAR). The fourth experiments shed light on the occurrence of Legionella, zoonotic and fungal pathogens in the rainwater harvesting systems (RWHS) situated in different regions of South Africa. Rainwater samples were collected in urban and semi-urban areas from tanks situated in various areas in South Africa (Johannesburg, Pretoria and Grahamstown). Pathogenic organisms investigated were Salmonella, Shigella, Vibrio cholerae, Legionella and fungal isolates. Pure isolates were obtained and screened using PCR. Results revealed the presence of pathogenic bacteria and fungi in all the tested RWHS. In Grahamstown the most detected pathogen was Salmonella (73%) while Vibrio Cholerae was not detected. All the tested pathogens were present from the RWHS situated in Pretoria. Shigella was not detected from the RWHS in Johannesburg while others were detected. Identification of fungal isolates from HRW showed the presence of pathogenic fungi such as Aspergillus fumigatus, Cryptococcus laurentii, Aureobasidium pullulans and Mucor circinelloides. The last experiments, focussed on exploring a suitable treatment method for HRW where a nano compound quaternary imidazolium modified montmorillonite (MMT) was used as a potential household rainwater treatment option. Harvested rainwater samples were collected from the RWHS situated at the Council for Scientific and Industrial Research (CSIR), Pretoria South Africa. River and borehole water samples were included in the study to check the efficiency of the treatment method on various water sources. River water samples were collected from Olifants River, Witbank, South Africa while borehole water was collected from a privately-owned borehole in Pretoria. For inoculation studies, all the water sources were sterilised in batches of 1 and 2 L and inoculated with approximately 107 CFU/mL of overnight E. coli. Approximately 200 mg of the quaternary imidazolium modified MMT was added to the inoculated water and samples collected immediately after inoculation (time 0) and thereafter every hour for 5 hrs. The analyses were further conducted using unsterilised water samples (total bacterial count) and 500 mg of the treatment material. Complete inactivation of E. coli in sterilised HRW was achieved in 2 hrs for the 2 L water samples and 3 hrs for the 1 L water samples. Sterilised river water achieved complete E. coli inactivation in 4 hrs for the 1 L and 5 hrs for the 2 L samples while borehole water samples achieved complete E. coli inactivation in 5 hrs (2 L) and 6 hrs for the 1 L samples. In the unsterilised water sources (total bacteria), complete bacterial inactivation was observed in 5 hrs for both the 1 and 2 L harvested rainwater samples, 6 hrs in river water samples (both 1 and 2 L) and 8 hrs for borehole water samples (1 and 2 L). The results suggest that the treatment option was more efficient in harvested rainwater (required less time for bacterial inactivation compared to river and borehole water). The results of the current study are of public health concern since the use of untreated HRW for potable purposes may pose a risk of transmission of pathogenic and antimicrobial-resistant E. coli and other pathogenic organisms such as Salmonella, Shigella and Vibrio cholerae. It is therefore recommended that in cases where the tested harvested rainwater is used for potable purposes, simple treatment methods such as boiling and SODIS be applied so the harvested rainwater is fit for human consumption.
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- Date Issued: 2020