Monitoring the impact of deforestation on an aquatic ecosystem using remote sensing: a case study of the Mngazana mangrove forest in the eastern cape province.
- Authors: Madasa, Akhona
- Date: 2020-12
- Subjects: Remote sensing , Mangrove forests , Climatic changes
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20815 , vital:46598
- Description: Coastal mangrove vegetation at Mngazana continues to be threatened and reduced periodically due to unmonitored harvesting. Covering an area of 148ha, the Mngazana mangrove forest remains unreserved, thus, research on the Mngazana mangroves is essential in order to monitor their state and sustainable management. Since in-situ monitoring of mangrove areas is both challenging and time-consuming, remote sensing technologies have been used to monitor these ecosystems. This study was carried out to monitor the impact of deforestation using ASTER satellite images over ten years: from 2008 - 2018. Validation was carried out by comparing classification results with the ground-referenced data, which yielded satisfactory agreement, with an overall accuracy of 94.64 percent and Kappa coefficient of 0.93 for 2008; and in 2009, the overall accuracy was 88.62 percent and a Kappa coefficient of 0.85. While the overall accuracy of 95.08 percent and a Kappa coefficient of 0.92 for 2016 and 2018 were observed, the overall accuracy of 93.58 percent and a Kappa coefficient of 0.91 was yielded. NDVI and SAVI indices were used as monitoring indicators. The results obtained in the study indicated that the canopy density of the mangrove forest remained unchanged in the years under investigation. However, insignificant changes in canopy density were identified between 2009 and 2016. , Thesis (MSc) (Applied Remote Sensing & GIS) -- University of Fort Hare, 2021
- Full Text:
- Authors: Madasa, Akhona
- Date: 2020-12
- Subjects: Remote sensing , Mangrove forests , Climatic changes
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20815 , vital:46598
- Description: Coastal mangrove vegetation at Mngazana continues to be threatened and reduced periodically due to unmonitored harvesting. Covering an area of 148ha, the Mngazana mangrove forest remains unreserved, thus, research on the Mngazana mangroves is essential in order to monitor their state and sustainable management. Since in-situ monitoring of mangrove areas is both challenging and time-consuming, remote sensing technologies have been used to monitor these ecosystems. This study was carried out to monitor the impact of deforestation using ASTER satellite images over ten years: from 2008 - 2018. Validation was carried out by comparing classification results with the ground-referenced data, which yielded satisfactory agreement, with an overall accuracy of 94.64 percent and Kappa coefficient of 0.93 for 2008; and in 2009, the overall accuracy was 88.62 percent and a Kappa coefficient of 0.85. While the overall accuracy of 95.08 percent and a Kappa coefficient of 0.92 for 2016 and 2018 were observed, the overall accuracy of 93.58 percent and a Kappa coefficient of 0.91 was yielded. NDVI and SAVI indices were used as monitoring indicators. The results obtained in the study indicated that the canopy density of the mangrove forest remained unchanged in the years under investigation. However, insignificant changes in canopy density were identified between 2009 and 2016. , Thesis (MSc) (Applied Remote Sensing & GIS) -- University of Fort Hare, 2021
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Thermal studies on three common mangrove-associated ectotherms in Mngazana Estuary, with emphasis on the survival of the salt marsh crab, Parasesarma catenatum (Ortman 1897
- Nonyukela, Asandiswa Simamkele
- Authors: Nonyukela, Asandiswa Simamkele
- Date: 2020-02
- Subjects: Mangrove forests
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20838 , vital:46627
- Description: Ecological data on the development and distribution of mangroves over time suggest that mangroves were strictly tropical in nature but have extended to higher latitudes during warmer periods. Species distribution models show that the mangrove range may have since 1963 expand by 17 km in 2020 and by as much as 68 km southwards by 2050. More climate data obtained, and modelling of future climate have increased interest in the thermal tolerance or organisms. Critical thermal maxima (CTMax) and thermal tolerance were employed to determine the thermal limits of common estuarine species associated with the mangrove forests at Mngazana Estuary. Three species were selected, each representing a medium within the mangrove environment: for water, i) Palaemon peringueyi; ii) for air, Cerithidea decollata; and iii) Parasesarma catenatum on the substratum. Animals were acclimated for 48 hrs following the thermal history of the environment. Each individual was exposed to constant rate of water temperature increase of 1°C.h-1. Different size classes (adult, sub-adult, juveniles) of crabs were used to determine the CTMax performance. Parasesarma catenatum showed intraspecific variability in CTMax in both air and water. Palaemon Peringueyi had a CTMax value of 33.8°C±1.96 while C. decollata had a CTMax of 39.6°C±2.76 and P. catenatum had a CTMax of 36,38 ±1,57 in water and 34,1 ±1,67 in air. Different size classes (Adult, Sub-adult, Juveniles) of crabs were used to further determine their CTMax performance. Parasesarma catenatum showed of intraspecific variability in CTMax in both air and water. Juvenile crabs showed higher CTMax in water than in air, while adult and sub-adults showed a higher CTMax in air. The size classes of P. catenatum (Adult, Sub-adult, Juveniles) were exposed to a range of salinity treatments from 5-65 for both shock and acclimated exposures. For acclimated exposures, crabs were acclimated down/up at change of 5-10 untill the test salinity was reached, at which point the crabs were exposed. For the shock exposure, the crabs were directly exposed to the test salinity from the holding salinity of 35. This study shows P. catenatum is euryhaline, tolerating salinities been 10 and 50. Survival was highest across all cohorts for the short-term (shock) exposure, suggesting prolonged exposure to hypo/hypersaline conditions may be detrimental for this keystone Mngazana Estuary species. Juven.ile populations showed the highest survival rate for both shock and acclimated exposure. This study highlights the importance of microhabitat variability and its effect on the tolerance of different species to abiotic factors and so may be useful in modelling the effects of climate change in these systems. , Thesis (MSc) (Zoology) -- University of Fort Hare, 2021
- Full Text:
- Authors: Nonyukela, Asandiswa Simamkele
- Date: 2020-02
- Subjects: Mangrove forests
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20838 , vital:46627
- Description: Ecological data on the development and distribution of mangroves over time suggest that mangroves were strictly tropical in nature but have extended to higher latitudes during warmer periods. Species distribution models show that the mangrove range may have since 1963 expand by 17 km in 2020 and by as much as 68 km southwards by 2050. More climate data obtained, and modelling of future climate have increased interest in the thermal tolerance or organisms. Critical thermal maxima (CTMax) and thermal tolerance were employed to determine the thermal limits of common estuarine species associated with the mangrove forests at Mngazana Estuary. Three species were selected, each representing a medium within the mangrove environment: for water, i) Palaemon peringueyi; ii) for air, Cerithidea decollata; and iii) Parasesarma catenatum on the substratum. Animals were acclimated for 48 hrs following the thermal history of the environment. Each individual was exposed to constant rate of water temperature increase of 1°C.h-1. Different size classes (adult, sub-adult, juveniles) of crabs were used to determine the CTMax performance. Parasesarma catenatum showed intraspecific variability in CTMax in both air and water. Palaemon Peringueyi had a CTMax value of 33.8°C±1.96 while C. decollata had a CTMax of 39.6°C±2.76 and P. catenatum had a CTMax of 36,38 ±1,57 in water and 34,1 ±1,67 in air. Different size classes (Adult, Sub-adult, Juveniles) of crabs were used to further determine their CTMax performance. Parasesarma catenatum showed of intraspecific variability in CTMax in both air and water. Juvenile crabs showed higher CTMax in water than in air, while adult and sub-adults showed a higher CTMax in air. The size classes of P. catenatum (Adult, Sub-adult, Juveniles) were exposed to a range of salinity treatments from 5-65 for both shock and acclimated exposures. For acclimated exposures, crabs were acclimated down/up at change of 5-10 untill the test salinity was reached, at which point the crabs were exposed. For the shock exposure, the crabs were directly exposed to the test salinity from the holding salinity of 35. This study shows P. catenatum is euryhaline, tolerating salinities been 10 and 50. Survival was highest across all cohorts for the short-term (shock) exposure, suggesting prolonged exposure to hypo/hypersaline conditions may be detrimental for this keystone Mngazana Estuary species. Juven.ile populations showed the highest survival rate for both shock and acclimated exposure. This study highlights the importance of microhabitat variability and its effect on the tolerance of different species to abiotic factors and so may be useful in modelling the effects of climate change in these systems. , Thesis (MSc) (Zoology) -- University of Fort Hare, 2021
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