A mechanistic and trait-based approach to investigating macroinvertebrates distribution and exposure to microplastics in riverine systems
- Authors: Owowenu, Enahoro Kennedy
- Date: 2024-10-11
- Subjects: Microplastics Environmental aspects , Water quality biological assessment , Hydrodynamics , Hydrogeomorphology , Biotope , Flow type
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466666 , vital:76765 , DOI https://doi.org/10.21504/10962/466666
- Description: Microplastics in rivers pose an ecological risk. Hydraulic biotopes form distinct flow patches that vary longitudinally along the river, potentially influencing the transport dynamics of microplastics. Macroinvertebrates exhibit adaptations to different hydraulic biotopes through their unique traits. These traits can mediate their exposure to microplastics, thereby imposing selective pressures on these organisms. Different taxa often demonstrate preferences for specific hydraulic biotopes characterized by distinct flow regimes. Understanding the transport dynamics of microplastics mediated by hydraulic biotopes and the potential exposure of macroinvertebrates at the hydraulic biotope scale is important for determining the fate of riverine microplastics and detecting species at risk. Both empirical and theoretical studies have highlighted the interconnectedness of hydrology, geomorphology, and microplastic transport in rivers, yet, there remains a gap in understanding how a hydro-geomorphological approach could enhance the understanding of the microplastic transport process. Little is known about the role of traits in driving macroinvertebrate exposure to microplastics at a scale relevant to ecological dynamics. This study addressed these gaps by applying a hydro-geomorphological approach to investigate the distribution of microplastics at the hydraulic biotope scale and assessed the potential exposure of macroinvertebrates using a trait-based approach. This study also explored the relationship between microplastic abundance and selected water physicochemical properties, as well as the influence of adjacent land use types. By integrating these aspects the research provided a comprehensive understanding of microplastics dynamics in river systems, shedding light on both environmental factors shaping their distribution and the potential impacts on aquatic organisms. The study was conducted over the wet and dry seasons (October 2021 – July 2022) at 10 sites located in the upper, middle, and lower reaches of the Swartkops and Buffalo River systems in the Eastern Cape Province of South Africa. The hydraulic biotopes (i.e., pools, runs, riffles) were grouped into two conceptualised forms, namely, sink and flush hydraulic zones and were characterized by hydraulic indices such as the Froude number and the Reynolds number. The flush hydraulic zone represents hydraulic biotopes where microplastics can potentially be remobilized quickly into suspension, and the sink represents biotopes where microplastics can potentially accumulate and remobilisation is far slower. Fast-to-moderate flowing hydraulic biotopes were conceptualised as microplastics flush zones while slow-flowing to still biotopes as microplastic sink zones. Samples were collected at different depths in each hydraulic zone to quantify suspended and settled forms of microplastics. Microplastics targeted in this study ranged in size from 0.063 mm to less than 5 mm. Classification was achieved through microscopic observation, and confirmation via Fourier Transform Infrared Spectroscopy (FTIR-ATR) was conducted for samples ranging from 0.5 mm to less than 5 mm. At the site level, settled microplastics showed statistically significant spatial and temporal variations between the sites, and between the seasons (P < 0.05). The suspended microplastic varied only spatially. Fibres and fragments were the dominant microplastic shape, while polyethylene and polypropylene were the dominant microplastic polymers. Suspended microplastics showed statistically significant variation between urban land cover and other land cover categories (industrial, agricultural, rural, and natural land cover). Microplastics abundance was associated with high levels of turbidity, total suspended solids, total inorganic nitrogen, higher temperatures and increasing electrical conductivity. At the hydraulic biotope scale, the mean occurrence of suspended microplastics (1.76 ± 1.44 items/L; mean + SD) in the flush hydraulic zone was higher than that in the sink zone (1.54 ± 1.46 items/L), while settled microplastics were more abundant in the sink hydraulic zone (1.82 ± 1.98 items/L) than the flush hydraulic zone (1.32 ± 1.49 items/L). This observation was in line with the prediction in this study. The mean suspended and settled microplastics concentrations were higher during the wet season across the flush and sink hydraulic zones than in the dry season. Global multivariate analysis of variance (MANOVA) and two-way analysis of variance (ANOVA) revealed significant spatial and temporal variations in settled microplastics abundances between the flush and sink hydraulic zones. The results indicated that geomorphologically defined units such as riffles and moderate to fast runs (flush) generally contained lower amounts of settled microplastics compared to pools and backwaters (sink). However, this distinction between the flush and sink microplastic zones was observed only for settled microplastics and not for suspended microplastics. Suspended and settled microplastics showed a statistically significant relationship with the Froude number index. The generalised additive model indicated that settled microplastics abundance distribution decreased significantly with increasing Froude number value in the flush zone. Suspended microplastics decreased at low Froude number values and showed an increasing trend at higher Froude number values of about 0.75. The results indicate the usefulness of the hydraulic biotope scale microplastic monitoring approach in detecting microplastic hotspots and explaining variations in microplastics abundances driven by instream hydraulics. Four traits and ecological preferences of macroinvertebrates including body size, gill type, feeding habit, and velocity preferences were selected and resolved into 17 trait attributes. The sink hydraulic zones such as pools were indicated to favour exposure to and ingestion of microplastics compared to the flush zones such as riffles and fast runs. Large body size macroinvertebrates were associated with the sink zone. Taxa with a very small body size had a higher likelihood for microplastics ingestion than taxa with other body sizes. Collectorgathering macroinvertebrates taxa that have operculate gills with small body sizes were more prone to exposure to microplastics in hydraulic biotopes with slow to very slow velocities. Fibres were the most abundant plastic ingested by macroinvertebrates preferring the flush zone while fibres and fragments were mostly ingested by those preferring the sink zones. The binomial logistic model revealed a highly significant result for the likelihood of operculate gill shape to clog in the sink hydraulic zone. The result of the binomial logistic regression indicates the usefulness of the trait-based approach for predicting exposure to microplastics. Overall, the study reveals the influences of hydro-geomorphological features on the transport dynamics of microplastics and the usefulness of the trait-based approach in the ecological study of microplastics in riverine systems. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Authors: Owowenu, Enahoro Kennedy
- Date: 2024-10-11
- Subjects: Microplastics Environmental aspects , Water quality biological assessment , Hydrodynamics , Hydrogeomorphology , Biotope , Flow type
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466666 , vital:76765 , DOI https://doi.org/10.21504/10962/466666
- Description: Microplastics in rivers pose an ecological risk. Hydraulic biotopes form distinct flow patches that vary longitudinally along the river, potentially influencing the transport dynamics of microplastics. Macroinvertebrates exhibit adaptations to different hydraulic biotopes through their unique traits. These traits can mediate their exposure to microplastics, thereby imposing selective pressures on these organisms. Different taxa often demonstrate preferences for specific hydraulic biotopes characterized by distinct flow regimes. Understanding the transport dynamics of microplastics mediated by hydraulic biotopes and the potential exposure of macroinvertebrates at the hydraulic biotope scale is important for determining the fate of riverine microplastics and detecting species at risk. Both empirical and theoretical studies have highlighted the interconnectedness of hydrology, geomorphology, and microplastic transport in rivers, yet, there remains a gap in understanding how a hydro-geomorphological approach could enhance the understanding of the microplastic transport process. Little is known about the role of traits in driving macroinvertebrate exposure to microplastics at a scale relevant to ecological dynamics. This study addressed these gaps by applying a hydro-geomorphological approach to investigate the distribution of microplastics at the hydraulic biotope scale and assessed the potential exposure of macroinvertebrates using a trait-based approach. This study also explored the relationship between microplastic abundance and selected water physicochemical properties, as well as the influence of adjacent land use types. By integrating these aspects the research provided a comprehensive understanding of microplastics dynamics in river systems, shedding light on both environmental factors shaping their distribution and the potential impacts on aquatic organisms. The study was conducted over the wet and dry seasons (October 2021 – July 2022) at 10 sites located in the upper, middle, and lower reaches of the Swartkops and Buffalo River systems in the Eastern Cape Province of South Africa. The hydraulic biotopes (i.e., pools, runs, riffles) were grouped into two conceptualised forms, namely, sink and flush hydraulic zones and were characterized by hydraulic indices such as the Froude number and the Reynolds number. The flush hydraulic zone represents hydraulic biotopes where microplastics can potentially be remobilized quickly into suspension, and the sink represents biotopes where microplastics can potentially accumulate and remobilisation is far slower. Fast-to-moderate flowing hydraulic biotopes were conceptualised as microplastics flush zones while slow-flowing to still biotopes as microplastic sink zones. Samples were collected at different depths in each hydraulic zone to quantify suspended and settled forms of microplastics. Microplastics targeted in this study ranged in size from 0.063 mm to less than 5 mm. Classification was achieved through microscopic observation, and confirmation via Fourier Transform Infrared Spectroscopy (FTIR-ATR) was conducted for samples ranging from 0.5 mm to less than 5 mm. At the site level, settled microplastics showed statistically significant spatial and temporal variations between the sites, and between the seasons (P < 0.05). The suspended microplastic varied only spatially. Fibres and fragments were the dominant microplastic shape, while polyethylene and polypropylene were the dominant microplastic polymers. Suspended microplastics showed statistically significant variation between urban land cover and other land cover categories (industrial, agricultural, rural, and natural land cover). Microplastics abundance was associated with high levels of turbidity, total suspended solids, total inorganic nitrogen, higher temperatures and increasing electrical conductivity. At the hydraulic biotope scale, the mean occurrence of suspended microplastics (1.76 ± 1.44 items/L; mean + SD) in the flush hydraulic zone was higher than that in the sink zone (1.54 ± 1.46 items/L), while settled microplastics were more abundant in the sink hydraulic zone (1.82 ± 1.98 items/L) than the flush hydraulic zone (1.32 ± 1.49 items/L). This observation was in line with the prediction in this study. The mean suspended and settled microplastics concentrations were higher during the wet season across the flush and sink hydraulic zones than in the dry season. Global multivariate analysis of variance (MANOVA) and two-way analysis of variance (ANOVA) revealed significant spatial and temporal variations in settled microplastics abundances between the flush and sink hydraulic zones. The results indicated that geomorphologically defined units such as riffles and moderate to fast runs (flush) generally contained lower amounts of settled microplastics compared to pools and backwaters (sink). However, this distinction between the flush and sink microplastic zones was observed only for settled microplastics and not for suspended microplastics. Suspended and settled microplastics showed a statistically significant relationship with the Froude number index. The generalised additive model indicated that settled microplastics abundance distribution decreased significantly with increasing Froude number value in the flush zone. Suspended microplastics decreased at low Froude number values and showed an increasing trend at higher Froude number values of about 0.75. The results indicate the usefulness of the hydraulic biotope scale microplastic monitoring approach in detecting microplastic hotspots and explaining variations in microplastics abundances driven by instream hydraulics. Four traits and ecological preferences of macroinvertebrates including body size, gill type, feeding habit, and velocity preferences were selected and resolved into 17 trait attributes. The sink hydraulic zones such as pools were indicated to favour exposure to and ingestion of microplastics compared to the flush zones such as riffles and fast runs. Large body size macroinvertebrates were associated with the sink zone. Taxa with a very small body size had a higher likelihood for microplastics ingestion than taxa with other body sizes. Collectorgathering macroinvertebrates taxa that have operculate gills with small body sizes were more prone to exposure to microplastics in hydraulic biotopes with slow to very slow velocities. Fibres were the most abundant plastic ingested by macroinvertebrates preferring the flush zone while fibres and fragments were mostly ingested by those preferring the sink zones. The binomial logistic model revealed a highly significant result for the likelihood of operculate gill shape to clog in the sink hydraulic zone. The result of the binomial logistic regression indicates the usefulness of the trait-based approach for predicting exposure to microplastics. Overall, the study reveals the influences of hydro-geomorphological features on the transport dynamics of microplastics and the usefulness of the trait-based approach in the ecological study of microplastics in riverine systems. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
Context-related drivers, occurrence and human exposure to antibiotic resistant Campylobacter in selected river systems in the Eastern Cape, South Africa
- Authors: Chibwe, Mary
- Date: 2024-10-11
- Subjects: Antibiotic resistance , Campylobacter , Health risk assessment , Drug resistance , Public health South Africa Eastern Cape , Polymerase chain reaction
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466644 , vital:76763 , DOI https://doi.org/10.21504/10962/466644
- Description: The increasing prevalence of antibiotic-resistant Campylobacter species in river systems is a growing public health concern globally. This challenge presents the need to understand the drivers influencing the occurrence of these antibiotic-resistant strains to inform effective mitigation strategies. Identifying local anthropogenic pressures/activities will enable tailored intervention and ensure that management efforts are targeted and effective in mitigating actual risks faced by local water resources. In particular, the occurrence of antibiotic-resistant Campylobacter in river systems causes concerns regarding potential human exposure. Campylobacter species are regularly implicated in both animal and human diarrhoea, and have gained recognition as one of the main causes of waterborne diseases. This study investigated context-related drivers to the presence of antibiotic-resistant Campylobacter, its occurrence, and the risk of human exposure in the Bloukrans and Swartkops rivers in the Eastern Cape, South Africa. The study utilised a questionnaire survey and focus group discussions to identify context-related sources and drivers of antibiotic-resistant bacteria and genes in the Bloukrans and Swartkops rivers. Additionally, physico-chemical analysis of water samples was done, and polymerase chain reaction (PCR) was employed to investigate occurrences of Campylobacter in both rivers, as well as the presence of virulent and antibiotic-resistant genes. Two control sites, one for each river, and a total of nine other sampling sites were selected for this study, four along the Bloukrans River and five along the Swartkops River. Water samples were collected from all eleven sites over a period of one year, covering all the seasons (winter, spring, summer and autumn). Exposure assessment was investigated by conducting propidium monoazide-quantitative polymerase chain reaction (PMA-qPCR) to quantify the concentration of viable Campylobacter and its antibiotic-resistance genes (ARGs) in the river water. The calculated concentration of viable Campylobacter and ARGs was then used to estimate human exposure dose of antibiotic-resistant Campylobacter via unintentional ingestion during swimming in the Bloukrans or Swartkops rivers. The questionnaire surveys and focus group discussions identified the factors of socio-demographic characteristics of the study catchments, lack of knowledge regarding antibiotic resistance, inappropriate antibiotic and disposal practices as well as anthropogenic activities (improper solid waste management, discharge of poorly treated wastewater, poor animal husbandry practices, urban run-off and storm water, industrial effluent and agricultural run-off) as context-related sources and drivers contributing to the emergence and of continuing occurrence antibiotic-resistant bacteria and genes in the Bloukrans and Swartkops rivers. The results obtained in this study suggest that the physiochemical properties of the water in the Bloukrans and Swartkops rivers are conducive for Campylobacter survival. The prevalence of Campylobacter was high at sites that recorded high turbidity, low dissolved oxygen and high conductivity. This study also highlighted the widespread and continual presence of Campylobacter spp. in the Bloukrans and Swartkops rivers, which are potentially antibiotic-resistant. The prevalence of Campylobacter was 60% virulence genes were detected at 15% (cadF), 10% (htrB), 10% (clpP), 5% (ciaB) and 5% (ctdC) for water samples from the Bloukrans River. Campylobacter was detected in 58% of water samples from the Swartkops River, while cadF, htrB, ciaB, clpP and ctdB were detected at 24%, 0%, 9.5%, 14.8% and 4.8%, respectively. Of the Campylobacter-positive water samples, the virulence genes cmeA, cmeB and cmeC were detected in 20%, 65% and 10% of the water samples from Bloukrans River, respectively. Similarly, the genes cmeA, cmeB and cmeC were detected at 14.3%, 52% and 9.5%, respectively, for the Swartkops River. Tetracycline resistance genes (tetO) were detected in 70% and 76% of the water samples collected from the Bloukrans and Swartkops rivers, respectively. It was also observed that the sampling site had a significant effect on the detection of Campylobacter for both rivers (p < 0.05). The prevalence of Campylobacter was higher for sites impacted by anthropogenic activities. The results show that sampling season had no significant effect on the occurrence of Campylobacter for both rivers. The analysis through PMA-qPCR revealed that the mean concentrations of the Campylobacter 16S rRNA gene from viable cells ranged from 2.1 × 104 to 1.75 × 105 copies/ml for the Bloukrans River, and from 0 (no detection) to 1.11 × 104 copies/ml (viable concentration) for the Swartkops River. The concentration of tetO from viable cells ranged from 4.75 × 101 to 2.71 × 103 copies/ml and 115.96 to 325.12 copies/ml, for the Bloukrans and Swartkops Rivers, respectively. Similarly, the concentration of cmeB genes from viable cells ranged from 7.8 × 101 to 2.76 × 104 copies/ml for the Bloukrans River and from 1.71 × 101 to 7.39 × 103 copies/ml for the Swartkops River. We utilized the calculated concentrations of viable Campylobacter 16S rRNA genes and ARGs to estimate the human intake burden of viable Campylobacter 16S rRNA copies per one-hour of swimming to range from 9.9 × 101 – 3.7 × 106 copies/h across the two rivers. The human intake burden of Campylobacter ARGs ranged from 3.6 × 102 – 5.8 × 105 copies/h for cmeB, and 9.98 × 102 – 5.7 × 104 copies/h for tetO. This study highlighted the intricate interplay of socio-demographic characteristics in the study catchments, such as insufficient awareness of antibiotic resistance, inappropriate antibiotic disposal practices and anthropogenic activities, which all contribute to the prevalence of antibiotic-resistant Campylobacter in the Bloukrans and Swartkops rivers, emphasizing the need for targeted interventions to address these specific influences. There is a potential risk of Campylobacter infections associated with human exposure to the rivers. This work contributes towards the body of knowledge in closing the current research gap on possible human exposure to antibiotic-resistant Campylobacter, and in general, exposure to ARBs through freshwater sources. The findings have practical implications for designing targeted interventions to mitigate these risks, to enhance the overall environmental and public health management in the region. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Authors: Chibwe, Mary
- Date: 2024-10-11
- Subjects: Antibiotic resistance , Campylobacter , Health risk assessment , Drug resistance , Public health South Africa Eastern Cape , Polymerase chain reaction
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466644 , vital:76763 , DOI https://doi.org/10.21504/10962/466644
- Description: The increasing prevalence of antibiotic-resistant Campylobacter species in river systems is a growing public health concern globally. This challenge presents the need to understand the drivers influencing the occurrence of these antibiotic-resistant strains to inform effective mitigation strategies. Identifying local anthropogenic pressures/activities will enable tailored intervention and ensure that management efforts are targeted and effective in mitigating actual risks faced by local water resources. In particular, the occurrence of antibiotic-resistant Campylobacter in river systems causes concerns regarding potential human exposure. Campylobacter species are regularly implicated in both animal and human diarrhoea, and have gained recognition as one of the main causes of waterborne diseases. This study investigated context-related drivers to the presence of antibiotic-resistant Campylobacter, its occurrence, and the risk of human exposure in the Bloukrans and Swartkops rivers in the Eastern Cape, South Africa. The study utilised a questionnaire survey and focus group discussions to identify context-related sources and drivers of antibiotic-resistant bacteria and genes in the Bloukrans and Swartkops rivers. Additionally, physico-chemical analysis of water samples was done, and polymerase chain reaction (PCR) was employed to investigate occurrences of Campylobacter in both rivers, as well as the presence of virulent and antibiotic-resistant genes. Two control sites, one for each river, and a total of nine other sampling sites were selected for this study, four along the Bloukrans River and five along the Swartkops River. Water samples were collected from all eleven sites over a period of one year, covering all the seasons (winter, spring, summer and autumn). Exposure assessment was investigated by conducting propidium monoazide-quantitative polymerase chain reaction (PMA-qPCR) to quantify the concentration of viable Campylobacter and its antibiotic-resistance genes (ARGs) in the river water. The calculated concentration of viable Campylobacter and ARGs was then used to estimate human exposure dose of antibiotic-resistant Campylobacter via unintentional ingestion during swimming in the Bloukrans or Swartkops rivers. The questionnaire surveys and focus group discussions identified the factors of socio-demographic characteristics of the study catchments, lack of knowledge regarding antibiotic resistance, inappropriate antibiotic and disposal practices as well as anthropogenic activities (improper solid waste management, discharge of poorly treated wastewater, poor animal husbandry practices, urban run-off and storm water, industrial effluent and agricultural run-off) as context-related sources and drivers contributing to the emergence and of continuing occurrence antibiotic-resistant bacteria and genes in the Bloukrans and Swartkops rivers. The results obtained in this study suggest that the physiochemical properties of the water in the Bloukrans and Swartkops rivers are conducive for Campylobacter survival. The prevalence of Campylobacter was high at sites that recorded high turbidity, low dissolved oxygen and high conductivity. This study also highlighted the widespread and continual presence of Campylobacter spp. in the Bloukrans and Swartkops rivers, which are potentially antibiotic-resistant. The prevalence of Campylobacter was 60% virulence genes were detected at 15% (cadF), 10% (htrB), 10% (clpP), 5% (ciaB) and 5% (ctdC) for water samples from the Bloukrans River. Campylobacter was detected in 58% of water samples from the Swartkops River, while cadF, htrB, ciaB, clpP and ctdB were detected at 24%, 0%, 9.5%, 14.8% and 4.8%, respectively. Of the Campylobacter-positive water samples, the virulence genes cmeA, cmeB and cmeC were detected in 20%, 65% and 10% of the water samples from Bloukrans River, respectively. Similarly, the genes cmeA, cmeB and cmeC were detected at 14.3%, 52% and 9.5%, respectively, for the Swartkops River. Tetracycline resistance genes (tetO) were detected in 70% and 76% of the water samples collected from the Bloukrans and Swartkops rivers, respectively. It was also observed that the sampling site had a significant effect on the detection of Campylobacter for both rivers (p < 0.05). The prevalence of Campylobacter was higher for sites impacted by anthropogenic activities. The results show that sampling season had no significant effect on the occurrence of Campylobacter for both rivers. The analysis through PMA-qPCR revealed that the mean concentrations of the Campylobacter 16S rRNA gene from viable cells ranged from 2.1 × 104 to 1.75 × 105 copies/ml for the Bloukrans River, and from 0 (no detection) to 1.11 × 104 copies/ml (viable concentration) for the Swartkops River. The concentration of tetO from viable cells ranged from 4.75 × 101 to 2.71 × 103 copies/ml and 115.96 to 325.12 copies/ml, for the Bloukrans and Swartkops Rivers, respectively. Similarly, the concentration of cmeB genes from viable cells ranged from 7.8 × 101 to 2.76 × 104 copies/ml for the Bloukrans River and from 1.71 × 101 to 7.39 × 103 copies/ml for the Swartkops River. We utilized the calculated concentrations of viable Campylobacter 16S rRNA genes and ARGs to estimate the human intake burden of viable Campylobacter 16S rRNA copies per one-hour of swimming to range from 9.9 × 101 – 3.7 × 106 copies/h across the two rivers. The human intake burden of Campylobacter ARGs ranged from 3.6 × 102 – 5.8 × 105 copies/h for cmeB, and 9.98 × 102 – 5.7 × 104 copies/h for tetO. This study highlighted the intricate interplay of socio-demographic characteristics in the study catchments, such as insufficient awareness of antibiotic resistance, inappropriate antibiotic disposal practices and anthropogenic activities, which all contribute to the prevalence of antibiotic-resistant Campylobacter in the Bloukrans and Swartkops rivers, emphasizing the need for targeted interventions to address these specific influences. There is a potential risk of Campylobacter infections associated with human exposure to the rivers. This work contributes towards the body of knowledge in closing the current research gap on possible human exposure to antibiotic-resistant Campylobacter, and in general, exposure to ARBs through freshwater sources. The findings have practical implications for designing targeted interventions to mitigate these risks, to enhance the overall environmental and public health management in the region. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
Microplastics as potential vectors for selected organic chemical pollutants in river ecosystems
- Authors: Tumwesigye, Edgar
- Date: 2024-10-11
- Subjects: Microplastics Environmental aspects , Vector , Adsorption (Biology) , Watersheds , Kinetics
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466677 , vital:76766 , DOI https://doi.org/10.21504/10962/466677
- Description: Microplastics (MPs) as pollutants in river ecosystems have received considerable research attention in recent years. However, in Africa, research on MPs is sparse, and more needs to be done. Empirical evidence suggests that MP can act as vectors of organic chemical pollutants due to their diverse functional groups and other physical-chemical properties, such as their small sizes, crystal structure and porosity. MPs acting as vectors of chemical pollutants, adds to the complexity of understanding the risk posed to both the ecosystem and human health. Regarding the so-called vector effect, the role of seasonality, land use type, adsorption kinetics, and MP properties has yet to receive the necessary research in the literature, especially concerning pharmaceutical active compounds and other organic pollutants in river systems. This is particularly true for Africa, including South Africa. This study, therefore, aimed to fill these existing research gaps. Overall, the study aimed to investigate the potential of selected microplastic polymers of a particular size range as vectors of organic pollutants in urban rivers within the Eastern Cape of South Africa. To achieve this aim, the study explored the influence of spatial-temporal variability, MPs particle sizes, and various physicochemical variables on the adsorption of antibiotics: Sulfamethoxazole, ciprofloxacin, and endocrine disruptors: 17β-Estradiol, 4-(2, 6-dimethyl-2-heptyl) phenol. The adsorption kinetics mechanism was also investigated and established. Polyethylene Terephthalate (PET) and polypropylene (PP) MPs were seasonally deployed once in the summer and autumn seasons, i.e. 20th January 2022 in Bloukrans River and 21st January 2022 in Swartkops River for the summer season and 7th April 2022 in Bloukrans River and 8th April 2022 in Swartkops River for the autumn season. Deployed MPs were of two size ranges, type 1 (2 mm<-≤5 mm) and type 2 (0.5mm<-≤2 mm). The sites where the MPs were deployed had different land use practices: informal settlements, discharge points of wastewater treatment works (WWTWs), agricultural farms, and control sites, considered as the least impacted sites. This was done to analyse land use types' role in the adsorption of chemical pollutants onto MPs. MPs were retrieved in periodic intervals of 7 days, 14 days and 35days calculated based on the day of deployment for both summer and autumn seasons and analysed for Sulfamethoxazole, Ciprofloxacin, 17β-Estradiol, 4-(2, 6-dimethyl-2-heptyl) phenol using high-resolution liquid chromatography–mass spectrometry LC-MS/MS equipped with a triple quadrupole (QqQ) analyser. Concurrent with MP retrieval water physicochemical variables: pH, dissolved oxygen (DO), temperature, turbidity, electrical conductivity (EC), total suspended solids (TSS), total dissolved solids, total alkalinity and total hardness. The adsorption kinetics mechanism was studied in the laboratory between PET and PP of two size ranges and Sulfamethoxazole, Ciprofloxacin, and 17β-Estradiol model chemical. The results indicate that land use practices significantly impacted the concentration of the adsorbed chemicals on MPs. Sites downstream of the WWTW had higher concentrations of Sulfamethoxazole: 11119.6001±12552.4120ngL-1 and ciprofloxacin: 30285.19± 28783.7821ngL-1 adsorbed onto MPs in the Bloukrans River compared to the concentration of same compounds from other land use types along the same River catchment. Agriculturally impacted sites had higher concentrations of 17β-Estradiol on MPs; 11624.5611 ± 15382.2923ngL-1 and 100.3635± 29.6321ngL-1 in Swartkops and Bloukrans Rivers respectively compared to other sites. These results suggest that land use is an essential factor influencing chemical inputs into rivers and their adsorption onto MPs. Adsorption was higher for the MP of smaller sizes compared to MPs with bigger sizes, indicating that size is an essential factor that influences the vector effects of MPs. Adsorption was significantly higher after 35 days than all other days during the two seasons (P< 0.05). The adoption kinetics data fitted well with the pseudo-second-order model (R2> 0.99), indicating that chemisorption mechanisms may be the rate-limiting step. Data did not fit the intraparticle diffusion model. Both film diffusion and intraparticle diffusion possibly influenced the rate-limiting adsorption step simultaneously. Regarding the relationship between adsorption and water physico-chemical variables, of special interest a positive correlation between total alkalinity, electrical conductivity, total hardness, and total suspended salts (TDS) and the concentration of the adsorbed chemicals was observed. While the relationship between adsorption and dissolved oxygen was negative. The physicochemical variables with a positive relationship with adsorption are indicative of pollution. Therefore, the result suggests that increasing pollution tends to favour higher adsorption. The results in this study highlight the insights on i) the influence of land use on adsorption, ii) the role of exposure duration on adsorption, iii) the influence of seasonality and MP sizes on adsorption iv) relationship between water physicochemical parameters and adsorption as well as v) establishing adsorption kinetic mechanism. These findings are critical to better understanding the so-called vector effects of MPs and the management associated with MPs in river systems and form essential data sets needed in developing effective pollution mitigation strategies that are region-specific. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Authors: Tumwesigye, Edgar
- Date: 2024-10-11
- Subjects: Microplastics Environmental aspects , Vector , Adsorption (Biology) , Watersheds , Kinetics
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466677 , vital:76766 , DOI https://doi.org/10.21504/10962/466677
- Description: Microplastics (MPs) as pollutants in river ecosystems have received considerable research attention in recent years. However, in Africa, research on MPs is sparse, and more needs to be done. Empirical evidence suggests that MP can act as vectors of organic chemical pollutants due to their diverse functional groups and other physical-chemical properties, such as their small sizes, crystal structure and porosity. MPs acting as vectors of chemical pollutants, adds to the complexity of understanding the risk posed to both the ecosystem and human health. Regarding the so-called vector effect, the role of seasonality, land use type, adsorption kinetics, and MP properties has yet to receive the necessary research in the literature, especially concerning pharmaceutical active compounds and other organic pollutants in river systems. This is particularly true for Africa, including South Africa. This study, therefore, aimed to fill these existing research gaps. Overall, the study aimed to investigate the potential of selected microplastic polymers of a particular size range as vectors of organic pollutants in urban rivers within the Eastern Cape of South Africa. To achieve this aim, the study explored the influence of spatial-temporal variability, MPs particle sizes, and various physicochemical variables on the adsorption of antibiotics: Sulfamethoxazole, ciprofloxacin, and endocrine disruptors: 17β-Estradiol, 4-(2, 6-dimethyl-2-heptyl) phenol. The adsorption kinetics mechanism was also investigated and established. Polyethylene Terephthalate (PET) and polypropylene (PP) MPs were seasonally deployed once in the summer and autumn seasons, i.e. 20th January 2022 in Bloukrans River and 21st January 2022 in Swartkops River for the summer season and 7th April 2022 in Bloukrans River and 8th April 2022 in Swartkops River for the autumn season. Deployed MPs were of two size ranges, type 1 (2 mm<-≤5 mm) and type 2 (0.5mm<-≤2 mm). The sites where the MPs were deployed had different land use practices: informal settlements, discharge points of wastewater treatment works (WWTWs), agricultural farms, and control sites, considered as the least impacted sites. This was done to analyse land use types' role in the adsorption of chemical pollutants onto MPs. MPs were retrieved in periodic intervals of 7 days, 14 days and 35days calculated based on the day of deployment for both summer and autumn seasons and analysed for Sulfamethoxazole, Ciprofloxacin, 17β-Estradiol, 4-(2, 6-dimethyl-2-heptyl) phenol using high-resolution liquid chromatography–mass spectrometry LC-MS/MS equipped with a triple quadrupole (QqQ) analyser. Concurrent with MP retrieval water physicochemical variables: pH, dissolved oxygen (DO), temperature, turbidity, electrical conductivity (EC), total suspended solids (TSS), total dissolved solids, total alkalinity and total hardness. The adsorption kinetics mechanism was studied in the laboratory between PET and PP of two size ranges and Sulfamethoxazole, Ciprofloxacin, and 17β-Estradiol model chemical. The results indicate that land use practices significantly impacted the concentration of the adsorbed chemicals on MPs. Sites downstream of the WWTW had higher concentrations of Sulfamethoxazole: 11119.6001±12552.4120ngL-1 and ciprofloxacin: 30285.19± 28783.7821ngL-1 adsorbed onto MPs in the Bloukrans River compared to the concentration of same compounds from other land use types along the same River catchment. Agriculturally impacted sites had higher concentrations of 17β-Estradiol on MPs; 11624.5611 ± 15382.2923ngL-1 and 100.3635± 29.6321ngL-1 in Swartkops and Bloukrans Rivers respectively compared to other sites. These results suggest that land use is an essential factor influencing chemical inputs into rivers and their adsorption onto MPs. Adsorption was higher for the MP of smaller sizes compared to MPs with bigger sizes, indicating that size is an essential factor that influences the vector effects of MPs. Adsorption was significantly higher after 35 days than all other days during the two seasons (P< 0.05). The adoption kinetics data fitted well with the pseudo-second-order model (R2> 0.99), indicating that chemisorption mechanisms may be the rate-limiting step. Data did not fit the intraparticle diffusion model. Both film diffusion and intraparticle diffusion possibly influenced the rate-limiting adsorption step simultaneously. Regarding the relationship between adsorption and water physico-chemical variables, of special interest a positive correlation between total alkalinity, electrical conductivity, total hardness, and total suspended salts (TDS) and the concentration of the adsorbed chemicals was observed. While the relationship between adsorption and dissolved oxygen was negative. The physicochemical variables with a positive relationship with adsorption are indicative of pollution. Therefore, the result suggests that increasing pollution tends to favour higher adsorption. The results in this study highlight the insights on i) the influence of land use on adsorption, ii) the role of exposure duration on adsorption, iii) the influence of seasonality and MP sizes on adsorption iv) relationship between water physicochemical parameters and adsorption as well as v) establishing adsorption kinetic mechanism. These findings are critical to better understanding the so-called vector effects of MPs and the management associated with MPs in river systems and form essential data sets needed in developing effective pollution mitigation strategies that are region-specific. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
Participatory mapping of key drivers of ecological change and analysing equity dimensions of ecosystem services flow in the Kat River Catchment
- Authors: Seriki, Esther Ahuoiza
- Date: 2024-10-11
- Subjects: Ecological change , Ecosystem services South Africa Kat River Valley , Participatory GIS , Freshwater ecosystem , Social equity
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465024 , vital:76566
- Description: Rivers are important ecosystems which supply ecosystem services critical to social-economic well-being. However, many rivers are degraded due to human activities. Degradation of river systems compromises the quality and quantity of ecosystem services they can supply. Managing important drivers of ecological change requires broad-based stakeholder participation to mobilise collective actions for an effective rehabilitation strategy. This study looked at two crucial research objectives in the Kat River catchment. The first was to undertake a multidimensional, participatory, engaged mapping of ecological changes, as well as current and changing ecosystem services in the Kat River catchment, and the second was to analyse the equity dimensions of ecosystem services flow in the Kat River catchment. Data were collected through semi-structured interviews and participatory GIS mapping exercises. A purposive sampling method was applied to recruit research participants for interviews and workshops. Between March 13th and May 31st, 2023, thirty-one (31) participants representing four social groups, non-farming individuals, catchment management forum members, commercial and subsistence farmers, participated in interviews. Additionally, twenty-two (22) stakeholders attended 2-day workshops held between 20−21 April 2022, and 30−31 May 2023. Data collected from interviews and workshops were analysed using thematic analysis. The results of stakeholder perceptions regarding the perceived ecological changes and their key drivers in the Kat River catchment revealed a concerning trend. Participants reported significant changes to the catchment area over time, including increased occurrences of flooding and water pollution and decreased aquatic biodiversity. Furthermore, degradation of ecosystem services, such as water quality, availability of medicinal plants, reeds, and fish populations, was noted. These environmental shifts have been accompanied by a rise in social-economic burdens, including the prevalence of water-borne diseases, cultural burdens (particularly the inability of certain groups to access ancestral grave sites) and declining fish populations. These findings emphasise the urgent need for intervention strategies to mitigate further degradation of the catchment area and safeguard the well-being of both the human population and the integrity of the ecosystems. Recommended intervention measures include improving wastewater management practices and creating targeted public awareness campaigns. By addressing these challenges, stakeholders can work towards preserving the integrity of the catchment area, protecting water resources and conserving biodiversity for future generations. The equity dimensions (distributive and procedural equity) analysis revealed notable disparities in access to the benefits of ecosystem services, as well as in participation of residents in the Kat River Water Users Association. Certain social groups, such as commercial farmers, were observed to receive more benefits from ecosystem services, while other groups, including the elderly and disabled individuals, seem to be negatively impacted by the activities of those who benefit most from ecosystem services in the Kat River catchment. This raises not only an equity issue but also the issue of how costs are externalised by certain groups. Of particular concern was the finding that seventy (70) per cent of the research participants were not aware of the presence of the Kat River Water Users Association, raising concerns about procedural equity in water resource management processes. Additionally, ninety (90) per cent of the participants had the perception that there was unfair water access and allocation across the various social groups, highlighting possible distributive inequities. The participants expressed a clear interest in learning more about the existence and operation of the Kat River Water Users Association, signalling a need for increased awareness and participation among social groups. Addressing these equity concerns is crucial to ensure that water resource management processes are designed to provide all stakeholders and water-dependent actors with equitable and fair access to decision making. Moving forward, efforts should be directed towards raising awareness of the Kat River Water Users Association and to promoting inclusive participation among all social groups. This awareness may involve targeted outreach campaigns, community engagement initiatives and policy reforms to foster more equitable water governance practices within the catchment. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Authors: Seriki, Esther Ahuoiza
- Date: 2024-10-11
- Subjects: Ecological change , Ecosystem services South Africa Kat River Valley , Participatory GIS , Freshwater ecosystem , Social equity
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/465024 , vital:76566
- Description: Rivers are important ecosystems which supply ecosystem services critical to social-economic well-being. However, many rivers are degraded due to human activities. Degradation of river systems compromises the quality and quantity of ecosystem services they can supply. Managing important drivers of ecological change requires broad-based stakeholder participation to mobilise collective actions for an effective rehabilitation strategy. This study looked at two crucial research objectives in the Kat River catchment. The first was to undertake a multidimensional, participatory, engaged mapping of ecological changes, as well as current and changing ecosystem services in the Kat River catchment, and the second was to analyse the equity dimensions of ecosystem services flow in the Kat River catchment. Data were collected through semi-structured interviews and participatory GIS mapping exercises. A purposive sampling method was applied to recruit research participants for interviews and workshops. Between March 13th and May 31st, 2023, thirty-one (31) participants representing four social groups, non-farming individuals, catchment management forum members, commercial and subsistence farmers, participated in interviews. Additionally, twenty-two (22) stakeholders attended 2-day workshops held between 20−21 April 2022, and 30−31 May 2023. Data collected from interviews and workshops were analysed using thematic analysis. The results of stakeholder perceptions regarding the perceived ecological changes and their key drivers in the Kat River catchment revealed a concerning trend. Participants reported significant changes to the catchment area over time, including increased occurrences of flooding and water pollution and decreased aquatic biodiversity. Furthermore, degradation of ecosystem services, such as water quality, availability of medicinal plants, reeds, and fish populations, was noted. These environmental shifts have been accompanied by a rise in social-economic burdens, including the prevalence of water-borne diseases, cultural burdens (particularly the inability of certain groups to access ancestral grave sites) and declining fish populations. These findings emphasise the urgent need for intervention strategies to mitigate further degradation of the catchment area and safeguard the well-being of both the human population and the integrity of the ecosystems. Recommended intervention measures include improving wastewater management practices and creating targeted public awareness campaigns. By addressing these challenges, stakeholders can work towards preserving the integrity of the catchment area, protecting water resources and conserving biodiversity for future generations. The equity dimensions (distributive and procedural equity) analysis revealed notable disparities in access to the benefits of ecosystem services, as well as in participation of residents in the Kat River Water Users Association. Certain social groups, such as commercial farmers, were observed to receive more benefits from ecosystem services, while other groups, including the elderly and disabled individuals, seem to be negatively impacted by the activities of those who benefit most from ecosystem services in the Kat River catchment. This raises not only an equity issue but also the issue of how costs are externalised by certain groups. Of particular concern was the finding that seventy (70) per cent of the research participants were not aware of the presence of the Kat River Water Users Association, raising concerns about procedural equity in water resource management processes. Additionally, ninety (90) per cent of the participants had the perception that there was unfair water access and allocation across the various social groups, highlighting possible distributive inequities. The participants expressed a clear interest in learning more about the existence and operation of the Kat River Water Users Association, signalling a need for increased awareness and participation among social groups. Addressing these equity concerns is crucial to ensure that water resource management processes are designed to provide all stakeholders and water-dependent actors with equitable and fair access to decision making. Moving forward, efforts should be directed towards raising awareness of the Kat River Water Users Association and to promoting inclusive participation among all social groups. This awareness may involve targeted outreach campaigns, community engagement initiatives and policy reforms to foster more equitable water governance practices within the catchment. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
Taxonomy- and trait-based responses of chironomid assemblage structure to pollution in selected urban rivers, Eastern Cape, South Africa
- Authors: Osoh, Miracle Ogagaoghene
- Date: 2024-10-11
- Subjects: Environmental monitoring , Chironomidae , Water quality , Urbanization , Aquatic insects , Aquatic ecology , Urban pollution
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466655 , vital:76764 , DOI https://doi.org/10.21504/10962/466655
- Description: Urbanisation, occasioned by an increasing human population and the proliferation of industries, is a major threat to freshwater resources and has been implicated as a cause of stream water quality deterioration, habitat degradation, and the loss of aquatic biodiversity. Pollution of freshwater systems resulting from urban-related activities severely alters stream ecosystem structure and function. To effectively protect and sustainably manage freshwater resources, it is important to develop biomonitoring tools which are both sensitive to changes in water quality conditions and can provide an understanding of the mechanisms by which urban pollution impacts freshwater ecosystems. In South Africa, the macroinvertebrate-based South African Scoring System version 5 (SASS5) is routinely used for water quality assessment. This tool is developed at the family level of taxonomic resolution, with the exception of a few taxa. This raises the question as to whether a species-level taxonomic approach, complemented with a trait-based approach could add additional value. This question was addressed comparatively by developing and applying a taxonomy- and trait-based approach using the taxonomically and functionally diverse Chironomidae family. Fifteen sites across three urban river systems (Buffalo, Bloukrans and Swartkops River systems) in the Eastern Cape Province of South Africa were purposefully selected for this study. Based on the predominant land use within the catchment of the sites and water quality variables, the study sites were grouped into five site categories. The least-impacted sites (REF) had 78.53% mean forested area, 5.98% mean urban area and 13.49% mean agricultural land. Sites that received diffuse pollution but were upstream from the effluent discharge point of wastewater treatment works (DP) had 59.07% mean forested area, 32.53% mean urban area and 6.20% mean agricultural land. Sites that received point source pollution from wastewater treatment works (PP) had 63.66% mean forested area, 26.26% mean urban area and 7.39% mean agricultural land. Sites further downstream from the wastewater treatment works that received impacts from both point source and diffuse pollution (AG) had 65.95% mean forested area, 18.24% mean urban area and 12.5% mean agricultural land. Sites selected for exploring the potential system recovery of the study rivers (RECV) had 77.21% mean forested area, 9.12% mean urban area and 10.7% mean agricultural land. Macroinvertebrates and physicochemical variables were sampled at sites in the Bloukrans and Buffalo rivers over four sampling events (spring, summer, winter, and autumn) between November 2021 and June 2022 using the SASS5 protocol. Historical chironomid and physicochemical data from the Swartkops River collected between 2009 and 2012 were also used in this study. The SASS5 family-level biotic index classified the water quality condition at the least impacted site (REF) of the Swartkops River as minimally impaired 80% of the time, compared to the chironomid-based multimetric index (CUMMI), which indicated that the water quality condition at this site was near-natural 50% of the time. The chironomid-based multimetric index and the SASS5 were divergent in their classification of water quality conditions at the DP and AG sites but were 100% in agreement regarding water quality conditions at the PP site as critically/severely modified. The SASS5 scores classified the water quality condition at the AG site as critically/severely modified 100% of the time, whereas the CUMMI index classified the water quality condition at this site as critically/severely modified 90% of the time but moderately modified 10% of the time. The results indicate that species-level and family-level indices tend to be in agreement for heavily impacted sites, but the same was not true for least or moderately impacted sites. Traits such as the possession of tracheal gills, very large body size, burrowing, whole-body undulation, construction of rigid tubes, possession of three tracheae, completion of lifecycle in more than one year, production of more than 1000 eggs per egg mass, preferences for fine detritus, and bivoltinism were deemed tolerant of urban pollution. Traits such as cuticular respiration, medium body size, predator feeding mode, completion of lifecycle within one year, and a preference for stone biotope were deemed sensitive to urban pollution. An approach was developed to classify chironomids into those that are potentially vulnerable and those that are resilient to urban pollution. The abundances of vulnerable species correlated positively with increasing dissolved oxygen and negatively with increasing turbidity, electrical conductivity, nitrite-nitrogen, ammonium-nitrogen, and orthophosphate-phosphorus. The relative abundance of the highly vulnerable species and that of the highly tolerant species responded significantly to urban pollution and differentiated between the site categories. The relative abundance of the highly vulnerable species was significantly different between the DP and PP site categories. The richness of vulnerable and highly vulnerable species was significantly different between the REF sites and the impacted site categories (DP, PP, and AG). These results indicated that the developed approach successfully predicted chironomid responses to urban pollution. Overall, the study makes important contributions to the field of freshwater biomonitoring. First, the study highlighted that species-level identification is necessary to differentiate sites which may be considered moderately impacted. Both family and species-level tools were sensitive to water quality conditions for least impacted and highly impacted sites, but the differences between the family-level and species-level indices were pronounced for sites considered moderately impacted. Second, a trait-based approach provided a mechanism for developing predictive tools, and in the case of this study, the potential resilience or vulnerability of chironomids was reliably predicted. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Authors: Osoh, Miracle Ogagaoghene
- Date: 2024-10-11
- Subjects: Environmental monitoring , Chironomidae , Water quality , Urbanization , Aquatic insects , Aquatic ecology , Urban pollution
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/466655 , vital:76764 , DOI https://doi.org/10.21504/10962/466655
- Description: Urbanisation, occasioned by an increasing human population and the proliferation of industries, is a major threat to freshwater resources and has been implicated as a cause of stream water quality deterioration, habitat degradation, and the loss of aquatic biodiversity. Pollution of freshwater systems resulting from urban-related activities severely alters stream ecosystem structure and function. To effectively protect and sustainably manage freshwater resources, it is important to develop biomonitoring tools which are both sensitive to changes in water quality conditions and can provide an understanding of the mechanisms by which urban pollution impacts freshwater ecosystems. In South Africa, the macroinvertebrate-based South African Scoring System version 5 (SASS5) is routinely used for water quality assessment. This tool is developed at the family level of taxonomic resolution, with the exception of a few taxa. This raises the question as to whether a species-level taxonomic approach, complemented with a trait-based approach could add additional value. This question was addressed comparatively by developing and applying a taxonomy- and trait-based approach using the taxonomically and functionally diverse Chironomidae family. Fifteen sites across three urban river systems (Buffalo, Bloukrans and Swartkops River systems) in the Eastern Cape Province of South Africa were purposefully selected for this study. Based on the predominant land use within the catchment of the sites and water quality variables, the study sites were grouped into five site categories. The least-impacted sites (REF) had 78.53% mean forested area, 5.98% mean urban area and 13.49% mean agricultural land. Sites that received diffuse pollution but were upstream from the effluent discharge point of wastewater treatment works (DP) had 59.07% mean forested area, 32.53% mean urban area and 6.20% mean agricultural land. Sites that received point source pollution from wastewater treatment works (PP) had 63.66% mean forested area, 26.26% mean urban area and 7.39% mean agricultural land. Sites further downstream from the wastewater treatment works that received impacts from both point source and diffuse pollution (AG) had 65.95% mean forested area, 18.24% mean urban area and 12.5% mean agricultural land. Sites selected for exploring the potential system recovery of the study rivers (RECV) had 77.21% mean forested area, 9.12% mean urban area and 10.7% mean agricultural land. Macroinvertebrates and physicochemical variables were sampled at sites in the Bloukrans and Buffalo rivers over four sampling events (spring, summer, winter, and autumn) between November 2021 and June 2022 using the SASS5 protocol. Historical chironomid and physicochemical data from the Swartkops River collected between 2009 and 2012 were also used in this study. The SASS5 family-level biotic index classified the water quality condition at the least impacted site (REF) of the Swartkops River as minimally impaired 80% of the time, compared to the chironomid-based multimetric index (CUMMI), which indicated that the water quality condition at this site was near-natural 50% of the time. The chironomid-based multimetric index and the SASS5 were divergent in their classification of water quality conditions at the DP and AG sites but were 100% in agreement regarding water quality conditions at the PP site as critically/severely modified. The SASS5 scores classified the water quality condition at the AG site as critically/severely modified 100% of the time, whereas the CUMMI index classified the water quality condition at this site as critically/severely modified 90% of the time but moderately modified 10% of the time. The results indicate that species-level and family-level indices tend to be in agreement for heavily impacted sites, but the same was not true for least or moderately impacted sites. Traits such as the possession of tracheal gills, very large body size, burrowing, whole-body undulation, construction of rigid tubes, possession of three tracheae, completion of lifecycle in more than one year, production of more than 1000 eggs per egg mass, preferences for fine detritus, and bivoltinism were deemed tolerant of urban pollution. Traits such as cuticular respiration, medium body size, predator feeding mode, completion of lifecycle within one year, and a preference for stone biotope were deemed sensitive to urban pollution. An approach was developed to classify chironomids into those that are potentially vulnerable and those that are resilient to urban pollution. The abundances of vulnerable species correlated positively with increasing dissolved oxygen and negatively with increasing turbidity, electrical conductivity, nitrite-nitrogen, ammonium-nitrogen, and orthophosphate-phosphorus. The relative abundance of the highly vulnerable species and that of the highly tolerant species responded significantly to urban pollution and differentiated between the site categories. The relative abundance of the highly vulnerable species was significantly different between the DP and PP site categories. The richness of vulnerable and highly vulnerable species was significantly different between the REF sites and the impacted site categories (DP, PP, and AG). These results indicated that the developed approach successfully predicted chironomid responses to urban pollution. Overall, the study makes important contributions to the field of freshwater biomonitoring. First, the study highlighted that species-level identification is necessary to differentiate sites which may be considered moderately impacted. Both family and species-level tools were sensitive to water quality conditions for least impacted and highly impacted sites, but the differences between the family-level and species-level indices were pronounced for sites considered moderately impacted. Second, a trait-based approach provided a mechanism for developing predictive tools, and in the case of this study, the potential resilience or vulnerability of chironomids was reliably predicted. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
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
- Full Text:
- 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
- Full Text:
Macroplastics in the environment: are they suitable habitats for macroinvertebrates in riverine systems?
- Authors: Ali, Andrew Abagai
- Date: 2023-10-13
- Subjects: Macroplastics , Aquatic invertebrates South Africa Eastern Cape , Experimental ecology , Plastic scrap , Environmental degradation , Functional ecology , Biotic communities
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424153 , vital:72128
- Description: Emerging pollutants, such as plastics are threat to freshwater ecosystems, and may negatively impact riverine systems. They can modify riverine habitats and affect aquatic organism distribution and composition. Knowledge of how macroplastics alter riverine habitat heterogeneity, and their effects on macroinvertebrate assemblage structure is sparse, especially in Africa. This study examines the effect of hydraulic biotopes on the colonisation, establishment and succession patterns of macroinvertebrates on macroplastic and natural substrates based on the taxonomic and trait-based approach. Four experimental sites from minimally impacted upper reaches of the Buffalo, Kat, Kowie, and Swartkops Rivers in the Eastern Cape of South Africa were selected for the deployment of plastic substrates. Plastics materials, including polyethylene terephthalate (PET) bottles and natural substrate composed of stone and vegetation, were used to formulate three substrate groups: Group 1: 100% natural substrates (NS), Group 2: 50% natural substrates and 50% plastic material (NP), and Group 3: 100% plastic materials (PD). These substrates were placed in litter bags of equal dimension (25 cm by 35 cm, with 2.5 cm mesh) and deployed randomly in three hydraulic biotopes (pools, riffles, runs) over a period of 180 days (October 2021 to April 2022). A total of 216 substrate bags, 54 bags per substrate were deployed per site in the four experimental sites. Twelve bags from each substrate group were retrieved at an interval of 30 days beginning on day 30 after deployment, and analysed for the establishment of macroinvertebrate communities. Based on composite hydraulic biotope data, Simpson index was significantly higher (P < 0.05) for macroinvertebrate assemblage structure on the 50% and 100% macroplastic substrate groups compared to natural substrates. With the exception of Tabanidae, Glossosomatidae, and Psephenidae, all macroinvertebrate taxa recorded showed non-significant positive correlations with all three substrate groups. However, Tabanidae, Glossosomatidae, and Psephenidae showed significant positive correlation with the 100% natural substrates, 50% plastic substrates and 100% plastic substrates, respectively. The parsimony analysis reveal that, within 30 days, all substrate groups underwent similar succession, with high abundance of pioneer taxa which increased on days 60 and 90, and then decreased from days 120 to 180. For the the pool biotope, Shannon and Simpson indices were significantly higher (P < 0.05) for the macroinvertabrates collected over the natural substates compared with those collected on the macroplastic substrate groups. However, in the riffle and run biotopes, all diversity indices were similar for all substrate groups and no statistically significant difference was observed. Statistically significant higher values for taxonomic richness, diversity, and evenness were found on day 30 to 90 for the riffle biotopes, and day 30 to 60 for the run biotopes. The run biotope presented temporal statistical significant variability in taxonomic composition with different macroinvertebrate communities recorded on days 30 and 60 compared with days 90 to 180. However, in pools and riffles, no temporal variation was observed in the taxonomic composition of macroinvertebrates on all three substrate groups. The trait-based fuzzy correspondence analysis revealed differential spatial-temporal distribution of macroinvertebrate traits on all three substrate group. The early colonisers i.e. day 30 – 60, were dominated by group of taxa characterised by medium (>10 – 20 mm) and large (20 > 40) body size, flat body, collector-gatherers, free-living, and predators. The late colonisers, collected mainly on day 150 and 180 were dominated by taxa with a preference for high flow velocity (0.3 - 0.6 m/s), permanent attachment, and filter-feeding mode. Traits such as oval and flat body shape, medium body size (>10 - 20 mm), skating and clinging/climbing mobility, temporal attachment, shredders, predators, prey, and plastron and spiracle respiration showed positive correlation with the 100% macroplastic substrates. Filter feeding, crawling, permanent attachment, a preference for fast velocity (0.3-0.6 m/s), and coarse particle organic matter were positively correlated with the 50% macroplastic substrates. Overall, the results provided critical insights on the impact of macroplastics on the assemblage structure of biological communities by acting as suitable habitats in stream ecosystems. The study elucidated the role of traits of aquatic organisms in mediating the colonisation of plastics substrates, providing insights into the impact of plastics proliferation on riverine ecosystem functioning. Furthermore, the finding provides a baseline insight into the influence of hydraulic biotopes on the colonisation and establishment of macroinvertebrates on macroplastic acting as artificial riverine habitat. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
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- Authors: Ali, Andrew Abagai
- Date: 2023-10-13
- Subjects: Macroplastics , Aquatic invertebrates South Africa Eastern Cape , Experimental ecology , Plastic scrap , Environmental degradation , Functional ecology , Biotic communities
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424153 , vital:72128
- Description: Emerging pollutants, such as plastics are threat to freshwater ecosystems, and may negatively impact riverine systems. They can modify riverine habitats and affect aquatic organism distribution and composition. Knowledge of how macroplastics alter riverine habitat heterogeneity, and their effects on macroinvertebrate assemblage structure is sparse, especially in Africa. This study examines the effect of hydraulic biotopes on the colonisation, establishment and succession patterns of macroinvertebrates on macroplastic and natural substrates based on the taxonomic and trait-based approach. Four experimental sites from minimally impacted upper reaches of the Buffalo, Kat, Kowie, and Swartkops Rivers in the Eastern Cape of South Africa were selected for the deployment of plastic substrates. Plastics materials, including polyethylene terephthalate (PET) bottles and natural substrate composed of stone and vegetation, were used to formulate three substrate groups: Group 1: 100% natural substrates (NS), Group 2: 50% natural substrates and 50% plastic material (NP), and Group 3: 100% plastic materials (PD). These substrates were placed in litter bags of equal dimension (25 cm by 35 cm, with 2.5 cm mesh) and deployed randomly in three hydraulic biotopes (pools, riffles, runs) over a period of 180 days (October 2021 to April 2022). A total of 216 substrate bags, 54 bags per substrate were deployed per site in the four experimental sites. Twelve bags from each substrate group were retrieved at an interval of 30 days beginning on day 30 after deployment, and analysed for the establishment of macroinvertebrate communities. Based on composite hydraulic biotope data, Simpson index was significantly higher (P < 0.05) for macroinvertebrate assemblage structure on the 50% and 100% macroplastic substrate groups compared to natural substrates. With the exception of Tabanidae, Glossosomatidae, and Psephenidae, all macroinvertebrate taxa recorded showed non-significant positive correlations with all three substrate groups. However, Tabanidae, Glossosomatidae, and Psephenidae showed significant positive correlation with the 100% natural substrates, 50% plastic substrates and 100% plastic substrates, respectively. The parsimony analysis reveal that, within 30 days, all substrate groups underwent similar succession, with high abundance of pioneer taxa which increased on days 60 and 90, and then decreased from days 120 to 180. For the the pool biotope, Shannon and Simpson indices were significantly higher (P < 0.05) for the macroinvertabrates collected over the natural substates compared with those collected on the macroplastic substrate groups. However, in the riffle and run biotopes, all diversity indices were similar for all substrate groups and no statistically significant difference was observed. Statistically significant higher values for taxonomic richness, diversity, and evenness were found on day 30 to 90 for the riffle biotopes, and day 30 to 60 for the run biotopes. The run biotope presented temporal statistical significant variability in taxonomic composition with different macroinvertebrate communities recorded on days 30 and 60 compared with days 90 to 180. However, in pools and riffles, no temporal variation was observed in the taxonomic composition of macroinvertebrates on all three substrate groups. The trait-based fuzzy correspondence analysis revealed differential spatial-temporal distribution of macroinvertebrate traits on all three substrate group. The early colonisers i.e. day 30 – 60, were dominated by group of taxa characterised by medium (>10 – 20 mm) and large (20 > 40) body size, flat body, collector-gatherers, free-living, and predators. The late colonisers, collected mainly on day 150 and 180 were dominated by taxa with a preference for high flow velocity (0.3 - 0.6 m/s), permanent attachment, and filter-feeding mode. Traits such as oval and flat body shape, medium body size (>10 - 20 mm), skating and clinging/climbing mobility, temporal attachment, shredders, predators, prey, and plastron and spiracle respiration showed positive correlation with the 100% macroplastic substrates. Filter feeding, crawling, permanent attachment, a preference for fast velocity (0.3-0.6 m/s), and coarse particle organic matter were positively correlated with the 50% macroplastic substrates. Overall, the results provided critical insights on the impact of macroplastics on the assemblage structure of biological communities by acting as suitable habitats in stream ecosystems. The study elucidated the role of traits of aquatic organisms in mediating the colonisation of plastics substrates, providing insights into the impact of plastics proliferation on riverine ecosystem functioning. Furthermore, the finding provides a baseline insight into the influence of hydraulic biotopes on the colonisation and establishment of macroinvertebrates on macroplastic acting as artificial riverine habitat. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2023
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