Pub Date : 2022-03-17DOI: 10.2989/16085914.2021.2003746
Getacher Beyene, D. Kifle, T. Fetahi
While scientific information on spatial variation of freshwater zooplankton is relevant to limnological studies, little information is available from the Ethiopian Rift Valley lake: Lake Hawassa. This study aimed at understanding the spatial distribution of the dominant zooplankton taxa in Lake Hawassa, Ethiopia. Collection of samples and in situ measurements of physico-chemical parameters were carried out at four sites for five consecutive months from April to August in 2019. Twenty-two species of zooplankton were identified. Among these, rotifers were the most important with regard to both species richness and abundance. Copepods were the second most important group in terms of species richness and abundance, whereas cladocerans were the least abundant taxa. All zooplankton groups were very rare at the inlet of the Tikur Wuha River, which could be mainly due to stress, associated with extreme turbidity. Rotifers were predominant at the inlet of influents from referral hospital revealing their adaptation to less clear water and pollution. Copepods attained their highest abundance at the macrophyte zone indicating their preference for water with high clarity and refuge. We concluded that the spatial variation of the zooplankton density in relation to water quality parameters has implications for the applicability of zooplankton as a cost-effective water quality assessment tool in lakes.
{"title":"Spatial distribution of zooplankton in relation to some selected physicochemical water quality parameters of Lake Hawassa, Ethiopia","authors":"Getacher Beyene, D. Kifle, T. Fetahi","doi":"10.2989/16085914.2021.2003746","DOIUrl":"https://doi.org/10.2989/16085914.2021.2003746","url":null,"abstract":"While scientific information on spatial variation of freshwater zooplankton is relevant to limnological studies, little information is available from the Ethiopian Rift Valley lake: Lake Hawassa. This study aimed at understanding the spatial distribution of the dominant zooplankton taxa in Lake Hawassa, Ethiopia. Collection of samples and in situ measurements of physico-chemical parameters were carried out at four sites for five consecutive months from April to August in 2019. Twenty-two species of zooplankton were identified. Among these, rotifers were the most important with regard to both species richness and abundance. Copepods were the second most important group in terms of species richness and abundance, whereas cladocerans were the least abundant taxa. All zooplankton groups were very rare at the inlet of the Tikur Wuha River, which could be mainly due to stress, associated with extreme turbidity. Rotifers were predominant at the inlet of influents from referral hospital revealing their adaptation to less clear water and pollution. Copepods attained their highest abundance at the macrophyte zone indicating their preference for water with high clarity and refuge. We concluded that the spatial variation of the zooplankton density in relation to water quality parameters has implications for the applicability of zooplankton as a cost-effective water quality assessment tool in lakes.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"163 - 172"},"PeriodicalIF":1.4,"publicationDate":"2022-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46278253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-03-07DOI: 10.2989/16085914.2021.2005527
Sadikiel E. Kaale, A. Mahadhy, Modester Damas, Clarence A. Mgina, T. Lyimo
The Momela soda lakes consist of seven small, hypersaline, alkaline lakes, situated in the East African rift valley at Arusha National Park, Tanzania. The lakes are fed by separate underground water sources with slightly varying mineral contents resulting in colour variation and supporting different kinds of prokaryotic and eukaryotic species. In this study, the diversity of Actinobacteria in surface water and sediments of five Lakes were investigated using culture-dependent and culture-independent molecular techniques. A total of 34 out of 112, and 13 out of 85, representatives of Actinobacteria isolates and clones, respectively, were selected for gene sequencing using the CD-HIT program. Analysis of their 16S rRNA gene sequences displayed the presence of species affiliated to 15 different genera, namely Mycobacterium, Rhodococcus, Microbacterium, Isoptericola, Dietzia, Leucobacter, Jonesia, Nesterenkonia, Micrococcus, Streptomyces, Hoyosella, Norcadiopsis, Cellulomonas, Bogoriella, and Agromyces. The results showed 5 and 12 putative new Actinobacteria isolates and clones, respectively. This is the first report of isolation of bacteria from the genus Mycobacterium from a soda lake globally, as well as the genera Hoyosella, Isoptericola, Jonesia, Micrococcus, Leucobacter and Agromyces from a soda lake in East Africa. Because Actinobacteria are known as a source of biotechnologically important compounds, the species revealed set a platform to search for novel bioactive compounds.
{"title":"Phylogenetic diversity of Actinobacteria from Momela soda lakes, Arusha National Park, Tanzania","authors":"Sadikiel E. Kaale, A. Mahadhy, Modester Damas, Clarence A. Mgina, T. Lyimo","doi":"10.2989/16085914.2021.2005527","DOIUrl":"https://doi.org/10.2989/16085914.2021.2005527","url":null,"abstract":"The Momela soda lakes consist of seven small, hypersaline, alkaline lakes, situated in the East African rift valley at Arusha National Park, Tanzania. The lakes are fed by separate underground water sources with slightly varying mineral contents resulting in colour variation and supporting different kinds of prokaryotic and eukaryotic species. In this study, the diversity of Actinobacteria in surface water and sediments of five Lakes were investigated using culture-dependent and culture-independent molecular techniques. A total of 34 out of 112, and 13 out of 85, representatives of Actinobacteria isolates and clones, respectively, were selected for gene sequencing using the CD-HIT program. Analysis of their 16S rRNA gene sequences displayed the presence of species affiliated to 15 different genera, namely Mycobacterium, Rhodococcus, Microbacterium, Isoptericola, Dietzia, Leucobacter, Jonesia, Nesterenkonia, Micrococcus, Streptomyces, Hoyosella, Norcadiopsis, Cellulomonas, Bogoriella, and Agromyces. The results showed 5 and 12 putative new Actinobacteria isolates and clones, respectively. This is the first report of isolation of bacteria from the genus Mycobacterium from a soda lake globally, as well as the genera Hoyosella, Isoptericola, Jonesia, Micrococcus, Leucobacter and Agromyces from a soda lake in East Africa. Because Actinobacteria are known as a source of biotechnologically important compounds, the species revealed set a platform to search for novel bioactive compounds.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"149 - 162"},"PeriodicalIF":1.4,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43682193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-28DOI: 10.2989/16085914.2021.2007044
Mk Reinecke, C. Brown, K. Esler, J. King
Riparian zones can be characterised botanically into two main areas, a wet bank and a dry bank. These areas have been linked to the duration of inundation by river flow, the boundary between the two being the 1:2 year floodline. Therefore the wet bank is inundated regularly by small floods and the dry bank by larger, less frequent floods, and each may support one to a few distinct plant communities laterally up the bank. Understanding these plant distributions helps rehabilitation projects and Environmental Flow (EFlows) studies as it can inform re-vegetation strategies in the former and help understanding of the links between plants and the river’s flow regime in the latter. Systematic sampling and data analysis methods were developed for single channel rivers with relatively undisturbed natural vegetation to identify and locate the different plant communities in the riparian zone. Generic rules using distance and height from the water’s edge, rather than the presence or absence of plant species, were calculated to locate the communities. While these statistics were derived from the riparian vegetation along perennial Western Cape rivers, South Africa, the methods could be applied to other perennial single channel river anywhere.
{"title":"Using riparian plant species to locate the 1:2-year floodline on single channel rivers","authors":"Mk Reinecke, C. Brown, K. Esler, J. King","doi":"10.2989/16085914.2021.2007044","DOIUrl":"https://doi.org/10.2989/16085914.2021.2007044","url":null,"abstract":"Riparian zones can be characterised botanically into two main areas, a wet bank and a dry bank. These areas have been linked to the duration of inundation by river flow, the boundary between the two being the 1:2 year floodline. Therefore the wet bank is inundated regularly by small floods and the dry bank by larger, less frequent floods, and each may support one to a few distinct plant communities laterally up the bank. Understanding these plant distributions helps rehabilitation projects and Environmental Flow (EFlows) studies as it can inform re-vegetation strategies in the former and help understanding of the links between plants and the river’s flow regime in the latter. Systematic sampling and data analysis methods were developed for single channel rivers with relatively undisturbed natural vegetation to identify and locate the different plant communities in the riparian zone. Generic rules using distance and height from the water’s edge, rather than the presence or absence of plant species, were calculated to locate the communities. While these statistics were derived from the riparian vegetation along perennial Western Cape rivers, South Africa, the methods could be applied to other perennial single channel river anywhere.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"245 - 258"},"PeriodicalIF":1.4,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48919952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-15DOI: 10.2989/16085914.2021.1982673
H. Dallas, N. Rivers‐Moore
Human activities have cumulatively altered natural thermal regimes, with impacts and occurrences of extreme events amplified and exacerbated by global climate change. This leads to cascading ecological impacts in river systems. This paper translates knowledge generated over more than ten years of thermal research in South Africa into a protocol for establishing environmental water temperature guidelines for perennial rivers in South Africa. Tools and protocols for generating thermal guidelines reflecting seasonal variation and daily ranges, setting ecologically relevant thermal targets, and approaches for incorporating water temperature into management plans are presented. Tools include a spatial (thermal) framework within which air-water temperature models are applied and reference thermographs are generated; national maps of system resilience and air-water temperature model accuracy; a database of variables likely to indicate system resilience and model accuracy; innovative tools for generating thermal metrics and thermographs; a screening process to assess thermal risk; and an evaluation process to assess thermal change based on deviation from reference or expected thermal conditions. The importance and value of thermal data was recognised by the freshwater community and collection of water temperature data strongly endorsed. Future rollout of a water temperature-monitoring programme for South Africa needs to be prioritised.
{"title":"A protocol and tools for setting environmental water temperature guidelines for perennial rivers in South Africa","authors":"H. Dallas, N. Rivers‐Moore","doi":"10.2989/16085914.2021.1982673","DOIUrl":"https://doi.org/10.2989/16085914.2021.1982673","url":null,"abstract":"Human activities have cumulatively altered natural thermal regimes, with impacts and occurrences of extreme events amplified and exacerbated by global climate change. This leads to cascading ecological impacts in river systems. This paper translates knowledge generated over more than ten years of thermal research in South Africa into a protocol for establishing environmental water temperature guidelines for perennial rivers in South Africa. Tools and protocols for generating thermal guidelines reflecting seasonal variation and daily ranges, setting ecologically relevant thermal targets, and approaches for incorporating water temperature into management plans are presented. Tools include a spatial (thermal) framework within which air-water temperature models are applied and reference thermographs are generated; national maps of system resilience and air-water temperature model accuracy; a database of variables likely to indicate system resilience and model accuracy; innovative tools for generating thermal metrics and thermographs; a screening process to assess thermal risk; and an evaluation process to assess thermal change based on deviation from reference or expected thermal conditions. The importance and value of thermal data was recognised by the freshwater community and collection of water temperature data strongly endorsed. Future rollout of a water temperature-monitoring programme for South Africa needs to be prioritised.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"275 - 290"},"PeriodicalIF":1.4,"publicationDate":"2022-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48616713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-04DOI: 10.2989/16085914.2021.2001308
M. Grenfell, T. Dube
This paper investigates the invasion of a reach of the Touws River by the deciduous alien tree Tamarix ramosissima Ledeb. (Pink Tamarisk, Saltcedar). The objectives of the paper were to investigate the utility of a delta-normalised difference vegetation index (dNDVI) in evaluating the status, pattern and process of invasion, and to evaluate the implications of the invasion for riverscape morphodynamics and physical habitat structure and function. The spectral classification developed had an overall accuracy of 59.89%, omission error of 28.25%, and commission error of 11.86%. The classification of vegetation was used to quantify the aerial extent and pattern of invasion (currently at least 65.50% of the valley floor vegetation cover). Field observations and existing knowledge of seed dispersal mechanisms and germination constraints of the invasive tree were compared with those of the indigenous sweet thorn Vachellia karroo, to provide insight into invasion patterns and processes within the reach. The linear channel-flanking distribution of the invasion has the potential to alter reach hydrology and morphodynamics, which are key building blocks of physical habitat structure and function. The spectral classification approach demonstrated is relatively simple, has a strong biophysical basis in that it exploits a known, predictable and observable seasonal vegetation response that produces a clear spectral signature, and can be applied to long reaches of rivers impacted by alien vegetation invasions.
{"title":"Spectral classification, mapping and physical habitat implications of a riparian invasion by Tamarix ramosissima Ledeb. in the Touws River, Klein Karoo, South Africa","authors":"M. Grenfell, T. Dube","doi":"10.2989/16085914.2021.2001308","DOIUrl":"https://doi.org/10.2989/16085914.2021.2001308","url":null,"abstract":"This paper investigates the invasion of a reach of the Touws River by the deciduous alien tree Tamarix ramosissima Ledeb. (Pink Tamarisk, Saltcedar). The objectives of the paper were to investigate the utility of a delta-normalised difference vegetation index (dNDVI) in evaluating the status, pattern and process of invasion, and to evaluate the implications of the invasion for riverscape morphodynamics and physical habitat structure and function. The spectral classification developed had an overall accuracy of 59.89%, omission error of 28.25%, and commission error of 11.86%. The classification of vegetation was used to quantify the aerial extent and pattern of invasion (currently at least 65.50% of the valley floor vegetation cover). Field observations and existing knowledge of seed dispersal mechanisms and germination constraints of the invasive tree were compared with those of the indigenous sweet thorn Vachellia karroo, to provide insight into invasion patterns and processes within the reach. The linear channel-flanking distribution of the invasion has the potential to alter reach hydrology and morphodynamics, which are key building blocks of physical habitat structure and function. The spectral classification approach demonstrated is relatively simple, has a strong biophysical basis in that it exploits a known, predictable and observable seasonal vegetation response that produces a clear spectral signature, and can be applied to long reaches of rivers impacted by alien vegetation invasions.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"197 - 206"},"PeriodicalIF":1.4,"publicationDate":"2022-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46597401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-09DOI: 10.2989/16085914.2021.1988888
W. Nesbitt, SB Clarke, LJ Chapman
Despite dramatic differences in calcium concentrations within aquatic systems, very few studies have explored the relationships between ambient calcium concentration and the calcium concentration of resident fish under natural conditions. This study compares calcium concentration in the water to that of the scales and vertebral column of the African cyprinid, Rastrineobola argentea from lakes Nabugabo and Victoria, East Africa. The concentration of calcium in Lake Nabugabo, which averaged 1.50 mg l−1, was much lower than the average of literature-derived values for the Ugandan portion of Lake Victoria (6.96 mg l−1). Rastrineobola argentea from Lake Victoria were characterised by higher levels of calcium in the scales than that of conspecifics from Lake Nabugabo, whereas there was no difference in vertebral column calcium concentration between the two populations. Within Lake Nabugabo, calcium concentration was lower in the scales than in the vertebral column of R. argentea, whereas no difference was detected between the scalar and vertebral calcium concentrations of conspecifics from Lake Victoria. These results suggest that ambient calcium concentration may affects tissue levels and that fish in Lake Nabugabo may remobilise calcium from their scales to maintain skeletal growth and development.
{"title":"Comparison of calcium concentration in scales and vertebral column of a cyprinid from calcium-limited environments in the Lake Victoria Basin, Uganda","authors":"W. Nesbitt, SB Clarke, LJ Chapman","doi":"10.2989/16085914.2021.1988888","DOIUrl":"https://doi.org/10.2989/16085914.2021.1988888","url":null,"abstract":"Despite dramatic differences in calcium concentrations within aquatic systems, very few studies have explored the relationships between ambient calcium concentration and the calcium concentration of resident fish under natural conditions. This study compares calcium concentration in the water to that of the scales and vertebral column of the African cyprinid, Rastrineobola argentea from lakes Nabugabo and Victoria, East Africa. The concentration of calcium in Lake Nabugabo, which averaged 1.50 mg l−1, was much lower than the average of literature-derived values for the Ugandan portion of Lake Victoria (6.96 mg l−1). Rastrineobola argentea from Lake Victoria were characterised by higher levels of calcium in the scales than that of conspecifics from Lake Nabugabo, whereas there was no difference in vertebral column calcium concentration between the two populations. Within Lake Nabugabo, calcium concentration was lower in the scales than in the vertebral column of R. argentea, whereas no difference was detected between the scalar and vertebral calcium concentrations of conspecifics from Lake Victoria. These results suggest that ambient calcium concentration may affects tissue levels and that fish in Lake Nabugabo may remobilise calcium from their scales to maintain skeletal growth and development.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"115 - 122"},"PeriodicalIF":1.4,"publicationDate":"2021-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48870792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-24DOI: 10.2989/16085914.2021.1982672
H. Dallas, J. Shelton, T. Sutton, Dimas Tri Cuptura, M. Kajee, N. Job
Access to long-term biodiversity datasets is vital for monitoring, managing and protecting freshwater ecosystems. Detecting critical ecosystem changes, such as losing unique biodiversity and ecosystem services, is dependent on access to data. A wealth of biodiversity data exists for river ecosystems in South Africa, but an operational information system to access these data is currently not available. This gap is the result of limited capacity for managing freshwater biodiversity data, with existing systems isolated, difficult to access and not well maintained. To address this knowledge gap, the Freshwater Biodiversity Information System (FBIS) has been developed. The FBIS is a powerful, visual, data-rich information system for hosting and serving freshwater biodiversity data. It serves as a platform for the inventory and maintenance of data, thereby facilitating the evaluation of long-term change in river biodiversity and ecosystem condition, and guiding future monitoring strategies and management decisions. System design and functionality was strongly informed by data and reporting needs of key end-user groups, including water resource managers, biodiversity and conservation managers and planners, scientific researchers, and environmental consultants. Future expansion aims to increase the diversity of data accessed, data flow, geographic coverage and strategically embed FBIS into South Africa’s main freshwater decision-making pipelines.
{"title":"The Freshwater Biodiversity Information System (FBIS) – mobilising data for evaluating long-term change in South African rivers","authors":"H. Dallas, J. Shelton, T. Sutton, Dimas Tri Cuptura, M. Kajee, N. Job","doi":"10.2989/16085914.2021.1982672","DOIUrl":"https://doi.org/10.2989/16085914.2021.1982672","url":null,"abstract":"Access to long-term biodiversity datasets is vital for monitoring, managing and protecting freshwater ecosystems. Detecting critical ecosystem changes, such as losing unique biodiversity and ecosystem services, is dependent on access to data. A wealth of biodiversity data exists for river ecosystems in South Africa, but an operational information system to access these data is currently not available. This gap is the result of limited capacity for managing freshwater biodiversity data, with existing systems isolated, difficult to access and not well maintained. To address this knowledge gap, the Freshwater Biodiversity Information System (FBIS) has been developed. The FBIS is a powerful, visual, data-rich information system for hosting and serving freshwater biodiversity data. It serves as a platform for the inventory and maintenance of data, thereby facilitating the evaluation of long-term change in river biodiversity and ecosystem condition, and guiding future monitoring strategies and management decisions. System design and functionality was strongly informed by data and reporting needs of key end-user groups, including water resource managers, biodiversity and conservation managers and planners, scientific researchers, and environmental consultants. Future expansion aims to increase the diversity of data accessed, data flow, geographic coverage and strategically embed FBIS into South Africa’s main freshwater decision-making pipelines.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"291 - 306"},"PeriodicalIF":1.4,"publicationDate":"2021-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42495327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.2989/16085914.2021.1993778
NC Ndlala, T. Dube
Wetland vegetation plays an important role in the environmental functioning of wetlands through the provision of ecosystem services, such as food and critical habitat for organisms that live in or near water resources. The ecosystem services provided by wetland vegetation are facing several pressures due to the impacts of drought. Drought can induce significant declines in overall plant productivity and even lead to high rates of plant mortality. Therefore, assessing vegetation response to a drought is important for wetland assessment. In this study, the subtle changes in vegetation distribution were used as a proxy to examine and quantify the extent of drought impacts on the Soetendalsvlei wetland within the Heuningnes Catchment, South Africa. First, the vegetation health information was extracted by calculating the Normalized Difference Vegetation Index (NDVI) during the wet and dry seasons for the period between 2014 and 2018. The derived NDVI results were further statistically linked to the corresponding rainfall and evapotranspiration observed during the study period. An analysis of NDVI results revealed that gradual vegetation health change occurred across the study area. The highest derived NDVI (0.5) for wetland vegetation was observed during 2014, but progressively declined over the years. Change in vegetation health indicated a significant (r = 0.8-0.92) and positive correlation to the amount of rainfall received over the same period, whereas with evapotranspiration the relationships showed an opposite trend (r = −0.7 to −0.5). The results of this study highlight the importance of integrating remotely sensed data and climate variability information in assessing wetland vegetation seasonal and long-term variations. Such information can help in decision-making on the conservation of wetlands and effective monitoring of wetland ecosystems.
{"title":"Use of remotely sensed derived metrics to assess wetland vegetation responses to climate variability-induced drought at the Soetendalsvlei wetland system in the Heuningnes Catchment, Western Cape province, South Africa","authors":"NC Ndlala, T. Dube","doi":"10.2989/16085914.2021.1993778","DOIUrl":"https://doi.org/10.2989/16085914.2021.1993778","url":null,"abstract":"Wetland vegetation plays an important role in the environmental functioning of wetlands through the provision of ecosystem services, such as food and critical habitat for organisms that live in or near water resources. The ecosystem services provided by wetland vegetation are facing several pressures due to the impacts of drought. Drought can induce significant declines in overall plant productivity and even lead to high rates of plant mortality. Therefore, assessing vegetation response to a drought is important for wetland assessment. In this study, the subtle changes in vegetation distribution were used as a proxy to examine and quantify the extent of drought impacts on the Soetendalsvlei wetland within the Heuningnes Catchment, South Africa. First, the vegetation health information was extracted by calculating the Normalized Difference Vegetation Index (NDVI) during the wet and dry seasons for the period between 2014 and 2018. The derived NDVI results were further statistically linked to the corresponding rainfall and evapotranspiration observed during the study period. An analysis of NDVI results revealed that gradual vegetation health change occurred across the study area. The highest derived NDVI (0.5) for wetland vegetation was observed during 2014, but progressively declined over the years. Change in vegetation health indicated a significant (r = 0.8-0.92) and positive correlation to the amount of rainfall received over the same period, whereas with evapotranspiration the relationships showed an opposite trend (r = −0.7 to −0.5). The results of this study highlight the importance of integrating remotely sensed data and climate variability information in assessing wetland vegetation seasonal and long-term variations. Such information can help in decision-making on the conservation of wetlands and effective monitoring of wetland ecosystems.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"185 - 196"},"PeriodicalIF":1.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43903507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.2989/16085914.2021.1987184
L. Marufu, C. Phiri, M. Barson, T. Nhiwatiwa
The stomach contents of tigerfish Hydrocynus vittatus, caught in an angling competition on Lake Kariba, were examined to determine the extent to which they feed on the invasive crayfish Cherax quadricarinatus. The stomach contents of 281 tigerfish caught during three tournaments (2013, 2014 and 2015) were examined and grouped into six main categories. The proportion of empty stomachs ranged from 4.6 to 13.9% in males and from 11.9 to 29.1% in females. The main food items according to the frequency of occurrence were fish (Limnothrissa miodon (69.0 ± 13.0%) fish remains (bones and scales; 33.0 ± 22.0%), Cichlidae (26.8 ± 2.10%) and Mormyridae (0.5 ± 0.9%) and invertebrates, such as crayfish (24.9 ± 4.6%) and insects (5.2 ± 2.1%). This tournament has been useful in confirming changes in tigerfish diet following the introduction and establishment of non-native species, such as Limnothrissa miodon and, more recently, the crayfish, C. quadricarinatus.
{"title":"Using the Kariba Invitation Tiger Fishing Tournament for monitoring an invasive crayfish Cherax quadricarinatus in Lake Kariba, Zimbabwe","authors":"L. Marufu, C. Phiri, M. Barson, T. Nhiwatiwa","doi":"10.2989/16085914.2021.1987184","DOIUrl":"https://doi.org/10.2989/16085914.2021.1987184","url":null,"abstract":"The stomach contents of tigerfish Hydrocynus vittatus, caught in an angling competition on Lake Kariba, were examined to determine the extent to which they feed on the invasive crayfish Cherax quadricarinatus. The stomach contents of 281 tigerfish caught during three tournaments (2013, 2014 and 2015) were examined and grouped into six main categories. The proportion of empty stomachs ranged from 4.6 to 13.9% in males and from 11.9 to 29.1% in females. The main food items according to the frequency of occurrence were fish (Limnothrissa miodon (69.0 ± 13.0%) fish remains (bones and scales; 33.0 ± 22.0%), Cichlidae (26.8 ± 2.10%) and Mormyridae (0.5 ± 0.9%) and invertebrates, such as crayfish (24.9 ± 4.6%) and insects (5.2 ± 2.1%). This tournament has been useful in confirming changes in tigerfish diet following the introduction and establishment of non-native species, such as Limnothrissa miodon and, more recently, the crayfish, C. quadricarinatus.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"123 - 125"},"PeriodicalIF":1.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42602774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.2989/16085914.2021.1976610
H. Bukhari, C. Brown
As human pressures on water resources increase, the data and decision support (DS) tools used in the governance, development and management of transboundary rivers are likely to become increasingly important. There are no universal, standardised selection processes or designs for these tools, and so it is up to individual River Basin Organisations (RBOs) to decide what to include in their capacities. This desktop study provides a broad comparative analysis of the suites of DS numerical modelling tools developed and utilised by five intergovernmental transboundary RBOs that advise their member states in the management of their shared water resources: the Permanent Okavango River Basin Water Commission; the Orange-Senqu River Commission; the Nile Basin Initiative; the Zambezi Watercourse Commission; and the Mekong River Commission. These DS tools were reviewed against the information required to enable the kinds of comprehensive assessments of proposed basin management and development plans defined in their respective agreements, which include not only hydrological parameters, but also environmental and social considerations. A review of the model development timelines showed that prior to 2000, little capacity existed in modelling of hydrological, ecosystem, and social components of the river, but that these gaps have been addressed in recent years.
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