The influence of the physical environment on invertebrate larval transport, settlement and recruitment with insights on early-stage physiological performance
- Authors: Duna, Oliver Olwethu
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435663 , vital:73177 , DOI 10.21504/10962/435663
- Description: Most marine benthic organisms have a biphasic life cycle whereby the larvae are pelagic, and their distribution, transport and settlement are largely controlled by environmental factors. Among these factors, hydrodynamics have key direct effects. Nearshore water hydrodynamics are strongly influenced by wind. This study investigated whether wind indirectly affects the distribution, settlement and recruitment of invertebrate marine larvae. Additionally, larvae are exposed to a more constant, benign environment than they will experience after settlement, and therefore the possible effects of larval thermal history on the physiological plasticity of settled organisms was also estimated for possible long-term insights into population dynamics. Four sites, two on the western and two on the eastern side of Algoa Bay in Gqeberha (formerly known as Port Elizabeth), South Africa, were chosen for larval collection. Sites at opposite ends of the bay were selected as they were towards either side of the dominant wind directions in this region. At each site, two sampling stations were identified at 300 and 900 metres offshore, with station replicates 300 metres apart. Sampling of marine invertebrate larvae was conducted after two days of westerly or easterly winds at either of the two western or eastern sites. The number of hours of unidirectional wind determined the prevalent wind on the two days prior to sampling. Samples were collected with a plankton pump at three depths; surface, mid-depth and bottom. Simultaneously with plankton sampling, water properties (fluorescence, temperature, zonal and meridional flow, salinity and oxygen) were measured. Settlement/recruitment samples of mussels and barnacles were collected at six sites, two at either edge of the bay and two within the center of the bay. Plastic scouring pads and PVC plastic plates covered with safety-walk, placed at least 30 cm from each other, were used to collect settlers/recruits of mussels and barnacles, respectively. The pads and plates were replaced on a monthly basis for 14 months to quantify monthly settlement/recruitment. At four of the six sites used for quantifying settlement/recruitment, settlers and recruits were collected to measure the physiological responses of these two ontogenetic stages (settlers and recruits) to acute temperature variations which they might experience in the intertidal zone. Three temperature loggers were used to record real time temperature variation at each site over the period (one month) in which the artificial collectors were in position. Factorial ANOVA was used to investigate the effects of wind, depth, site, and distance from the shore on the abundance of larvae in the water column, as well as the effects of month and site on settlement/recruitment. Additionally, multiple regression analyses were used to investigate the effects of physical parameters, including upwelling and dissipation of turbulent kinetic energy, on the abundance of both larvae, settlers and recruits. Distance-based linear models and redundancy analyses were also carried out on the abundances of invertebrate larvae. Correlation analyses were performed to investigate the effect of the number of hours of directional wind on settlement. Lastly, correlation analyses between wind and currents were carried out. The results revealed a link between winds and currents, with wind speed directly proportional to surface current speed, which, as expected, decreased with depth. Current direction was, however, not perfectly aligned with wind direction. Larval distribution, settlement and recruitment were largely associated with the nearshore dissipation of turbulent kinetic energy and upwelling. Thus, overall larval, settler and recruit abundances were indirectly affected by wind. Physiologically, there was no significant difference in oxygen consumption between the juvenile ontogenetic stages (settlers and recruits) of mussels. Recruits exposed to average and maximum temperatures, however, consumed more oxygen than those exposed to low temperatures. Wind and wind-mediated currents as well as temperature have been shown to shape the distribution and shore supply of larvae, and this study contributes to the broad knowledge of population dynamics and replenishment, and the tight relation of abiotic factors affecting biological processes on the shore. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
- Authors: Duna, Oliver Olwethu
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435663 , vital:73177 , DOI 10.21504/10962/435663
- Description: Most marine benthic organisms have a biphasic life cycle whereby the larvae are pelagic, and their distribution, transport and settlement are largely controlled by environmental factors. Among these factors, hydrodynamics have key direct effects. Nearshore water hydrodynamics are strongly influenced by wind. This study investigated whether wind indirectly affects the distribution, settlement and recruitment of invertebrate marine larvae. Additionally, larvae are exposed to a more constant, benign environment than they will experience after settlement, and therefore the possible effects of larval thermal history on the physiological plasticity of settled organisms was also estimated for possible long-term insights into population dynamics. Four sites, two on the western and two on the eastern side of Algoa Bay in Gqeberha (formerly known as Port Elizabeth), South Africa, were chosen for larval collection. Sites at opposite ends of the bay were selected as they were towards either side of the dominant wind directions in this region. At each site, two sampling stations were identified at 300 and 900 metres offshore, with station replicates 300 metres apart. Sampling of marine invertebrate larvae was conducted after two days of westerly or easterly winds at either of the two western or eastern sites. The number of hours of unidirectional wind determined the prevalent wind on the two days prior to sampling. Samples were collected with a plankton pump at three depths; surface, mid-depth and bottom. Simultaneously with plankton sampling, water properties (fluorescence, temperature, zonal and meridional flow, salinity and oxygen) were measured. Settlement/recruitment samples of mussels and barnacles were collected at six sites, two at either edge of the bay and two within the center of the bay. Plastic scouring pads and PVC plastic plates covered with safety-walk, placed at least 30 cm from each other, were used to collect settlers/recruits of mussels and barnacles, respectively. The pads and plates were replaced on a monthly basis for 14 months to quantify monthly settlement/recruitment. At four of the six sites used for quantifying settlement/recruitment, settlers and recruits were collected to measure the physiological responses of these two ontogenetic stages (settlers and recruits) to acute temperature variations which they might experience in the intertidal zone. Three temperature loggers were used to record real time temperature variation at each site over the period (one month) in which the artificial collectors were in position. Factorial ANOVA was used to investigate the effects of wind, depth, site, and distance from the shore on the abundance of larvae in the water column, as well as the effects of month and site on settlement/recruitment. Additionally, multiple regression analyses were used to investigate the effects of physical parameters, including upwelling and dissipation of turbulent kinetic energy, on the abundance of both larvae, settlers and recruits. Distance-based linear models and redundancy analyses were also carried out on the abundances of invertebrate larvae. Correlation analyses were performed to investigate the effect of the number of hours of directional wind on settlement. Lastly, correlation analyses between wind and currents were carried out. The results revealed a link between winds and currents, with wind speed directly proportional to surface current speed, which, as expected, decreased with depth. Current direction was, however, not perfectly aligned with wind direction. Larval distribution, settlement and recruitment were largely associated with the nearshore dissipation of turbulent kinetic energy and upwelling. Thus, overall larval, settler and recruit abundances were indirectly affected by wind. Physiologically, there was no significant difference in oxygen consumption between the juvenile ontogenetic stages (settlers and recruits) of mussels. Recruits exposed to average and maximum temperatures, however, consumed more oxygen than those exposed to low temperatures. Wind and wind-mediated currents as well as temperature have been shown to shape the distribution and shore supply of larvae, and this study contributes to the broad knowledge of population dynamics and replenishment, and the tight relation of abiotic factors affecting biological processes on the shore. , Thesis (PhD) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-05
Assessing rural senior primary school natural science teachers’ TPACK: a case study
- Authors: Silvanus, Secilia Tulikefo
- Date: 2024-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/423902 , vital:72103
- Description: In today's world, technology has changed how people live and behave. The influence of technology contemplates a similar change in the education processes of teaching and learning. Many governments worldwide invest hugely in providing technological tools and facilities and training teachers to improve teaching and learning. The availability and access to technologies in schools seem to offer teachers opportunities to develop technological knowledge and integrate technology into teaching. Literature indicates that teachers must possess technological pedagogical content knowledge (TPACK) to integrate technology into teaching and learning processes effectively. However, other scholars have also suggested that teachers' TPACK develops and is shaped by many contexts. This study, therefore, sought to assess the rural senior primary Natural science teachers' TPACK. This qualitative case study was conducted with senior primary Natural science teachers in the educational circuit of Endola. An interpretive paradigm underpinned the study. The study employed semi-structured questionnaires, semi-structured interviews, focus group interviews, and observation to collect the data. The study used the TPACK as a theoretical and analytical framework. The study results showed that participants had a firmer grasp of subject content (CK) and traditional teaching methods (Pedagogical Knowledge - PK and Pedagogical Content Knowledge - PCK) compared to technological knowledge (TK) and technology-based pedagogies (Technological Pedagogical Knowledge - TPK, Technological Content Knowledge - TCK, and Technological Pedagogical Content Knowledge (TPCK). Findings support that the participants draw upon sources of Technological Pedagogical Content Knowledge (TPACK) closely aligned with Content Knowledge (CK), Technological Content Knowledge (TCK), and Technological Pedagogical Knowledge (TPK) to integrate technology. The study included inadequate professional development, teachers' attitudes, insufficient hardware and internet connectivity, limited technological knowledge, time constraints, and restricted access to technology tools and resources as obstacles for teachers attempting to incorporate technology into their classrooms effectively. Furthermore, the data highlights ICT training and teachers' interest as enablers that motivated participants to integrate technology into their teaching practices. Therefore, the study recommends professional development programs focusing on providing science teachers with practical skills to utilise different technologies and address common technical issues. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Silvanus, Secilia Tulikefo
- Date: 2024-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/423902 , vital:72103
- Description: In today's world, technology has changed how people live and behave. The influence of technology contemplates a similar change in the education processes of teaching and learning. Many governments worldwide invest hugely in providing technological tools and facilities and training teachers to improve teaching and learning. The availability and access to technologies in schools seem to offer teachers opportunities to develop technological knowledge and integrate technology into teaching. Literature indicates that teachers must possess technological pedagogical content knowledge (TPACK) to integrate technology into teaching and learning processes effectively. However, other scholars have also suggested that teachers' TPACK develops and is shaped by many contexts. This study, therefore, sought to assess the rural senior primary Natural science teachers' TPACK. This qualitative case study was conducted with senior primary Natural science teachers in the educational circuit of Endola. An interpretive paradigm underpinned the study. The study employed semi-structured questionnaires, semi-structured interviews, focus group interviews, and observation to collect the data. The study used the TPACK as a theoretical and analytical framework. The study results showed that participants had a firmer grasp of subject content (CK) and traditional teaching methods (Pedagogical Knowledge - PK and Pedagogical Content Knowledge - PCK) compared to technological knowledge (TK) and technology-based pedagogies (Technological Pedagogical Knowledge - TPK, Technological Content Knowledge - TCK, and Technological Pedagogical Content Knowledge (TPCK). Findings support that the participants draw upon sources of Technological Pedagogical Content Knowledge (TPACK) closely aligned with Content Knowledge (CK), Technological Content Knowledge (TCK), and Technological Pedagogical Knowledge (TPK) to integrate technology. The study included inadequate professional development, teachers' attitudes, insufficient hardware and internet connectivity, limited technological knowledge, time constraints, and restricted access to technology tools and resources as obstacles for teachers attempting to incorporate technology into their classrooms effectively. Furthermore, the data highlights ICT training and teachers' interest as enablers that motivated participants to integrate technology into their teaching practices. Therefore, the study recommends professional development programs focusing on providing science teachers with practical skills to utilise different technologies and address common technical issues. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-04
Technological Pedagogical Content Knowledge (TPACK): investigating senior primary mathematics teachers’ integration of technology in the classroom in Okahao educational circuit
- Shikesho, Hilya Ndahambelela
- Authors: Shikesho, Hilya Ndahambelela
- Date: 2024-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/423913 , vital:72104
- Description: Access restricted. Expected release date 2025. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-04
- Authors: Shikesho, Hilya Ndahambelela
- Date: 2024-04
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/423913 , vital:72104
- Description: Access restricted. Expected release date 2025. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
- Full Text:
- Date Issued: 2024-04
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