Pub Date : 2022-04-03DOI: 10.2989/16085914.2022.2044749
TM Agblonon Houelome, TP Agbohessi, D. Adandédjan, R. Nechifor, A. Chikou, IM Lazar, P. Lalèyè
The Alibori River, which flows through Benin’s cotton crop regions, receives surface water from much of the cultivated land that is situated along its banks. Chemical pollution in surface runoff from this land use threatens the ecological quality of the river. This study aimed to characterise the ecological status of the Alibori River under such agricultural pressures using biological indices and macroinvertebrate metrics. Water and macroinvertebrate samples were taken monthly from fifteen sites along the river between June 2015 and May 2016. The measured physico-chemical parameters and biological indices were subjected to descriptive statistics, bivariate correlations and partial least squares regression (PLSR). Taxonomic richness decreased from the upstream to the downstream reaches of the river. Sampling sites with high mineral content and organic load were home to more pollution-tolerant taxa, such as Chironomidae and Oligochaeta, with a high abundance of Thiaridae. Diversity indices reveal an unbalanced community and macroinvertebrate distribution characterised by the development of opportunistic taxa such as the gastropod Melanoides tuberculata. Decreases in taxonomic composition and community organisation between the upstream and downstream reaches of the river appear to be linked to less stable environmental conditions at the downstream sampling sites, and were compounded with a gradual increase in stress for organisms from the upper to lower reaches of the river. The composition, distribution and diversity characteristics of taxa collected is an indication that the ecological status of the Alibori River is under pressure, as a result of the agricultural activities along its banks.
{"title":"Ecological quality of the Alibori River, northern Benin, using macroinvertebrate indicators","authors":"TM Agblonon Houelome, TP Agbohessi, D. Adandédjan, R. Nechifor, A. Chikou, IM Lazar, P. Lalèyè","doi":"10.2989/16085914.2022.2044749","DOIUrl":"https://doi.org/10.2989/16085914.2022.2044749","url":null,"abstract":"The Alibori River, which flows through Benin’s cotton crop regions, receives surface water from much of the cultivated land that is situated along its banks. Chemical pollution in surface runoff from this land use threatens the ecological quality of the river. This study aimed to characterise the ecological status of the Alibori River under such agricultural pressures using biological indices and macroinvertebrate metrics. Water and macroinvertebrate samples were taken monthly from fifteen sites along the river between June 2015 and May 2016. The measured physico-chemical parameters and biological indices were subjected to descriptive statistics, bivariate correlations and partial least squares regression (PLSR). Taxonomic richness decreased from the upstream to the downstream reaches of the river. Sampling sites with high mineral content and organic load were home to more pollution-tolerant taxa, such as Chironomidae and Oligochaeta, with a high abundance of Thiaridae. Diversity indices reveal an unbalanced community and macroinvertebrate distribution characterised by the development of opportunistic taxa such as the gastropod Melanoides tuberculata. Decreases in taxonomic composition and community organisation between the upstream and downstream reaches of the river appear to be linked to less stable environmental conditions at the downstream sampling sites, and were compounded with a gradual increase in stress for organisms from the upper to lower reaches of the river. The composition, distribution and diversity characteristics of taxa collected is an indication that the ecological status of the Alibori River is under pressure, as a result of the agricultural activities along its banks.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"173 - 184"},"PeriodicalIF":1.4,"publicationDate":"2022-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45591365","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 : 2022-04-03DOI: 10.2989/16085914.2022.2041387
FJ Jacobs, T. Naesje, EM Ulvan, C. Hay, FH Khaebeb, O. Weyl
The fishery for the African tigerfish Hydrocynus vittatus in northern Namibia makes a substantial contribution to surrounding food security and stimulates the local economy through subsistence and recreational fishing. However, local fishers suggest that catch rates of H. vittatus have declined and the fish are now smaller. The Namibian Ministry of Fisheries and Marine Resources conducted annual gill net surveys in the Kavango River from 1994 to 2018. These standardised surveys were used to compare catch per unit effort data and length frequencies of H. vittatus between intensively fished areas and a freshwater protected area (FPA). The catch per unit effort (by numbers and mass) and proportion (56% vs 10–20%) of mature fish (males >180 mm fork length and females >280 mm fork length) were higher inside the FPA, compared with those outside. The H. vittatus populations, both outside and inside the FPA, are subject to overfishing and management actions should be taken to secure this important fishery resource for subsistence and recreational fishers.
纳米比亚北部的非洲虎鱼(Hydrocynus vittatus)渔业为周围的粮食安全作出了重大贡献，并通过自给和休闲捕鱼刺激了当地经济。然而，当地渔民表示，维塔图鱼的捕捞率已经下降，鱼现在更小了。从1994年到2018年，纳米比亚渔业和海洋资源部在Kavango河进行了年度刺网调查。这些标准化调查用于比较集约捕捞区和淡水保护区(FPA)之间的单位努力渔获量数据和维塔图鱼长度频率。成熟鱼(雄鱼叉长180 mm，雌鱼叉长280 mm)的单位努力渔获量(按数量和质量计算)和比例(56% vs 10-20%)在FPA内高于FPA外。保护区内外的维塔塔鱼种群都受到过度捕捞的影响，应采取管理行动，确保这一重要的渔业资源，供生计和休闲渔民使用。
{"title":"Evidence for overfishing of tigerfish Hydrocynus vittatus (Castelnau 1861) in the Kavango River, Namibia","authors":"FJ Jacobs, T. Naesje, EM Ulvan, C. Hay, FH Khaebeb, O. Weyl","doi":"10.2989/16085914.2022.2041387","DOIUrl":"https://doi.org/10.2989/16085914.2022.2041387","url":null,"abstract":"The fishery for the African tigerfish Hydrocynus vittatus in northern Namibia makes a substantial contribution to surrounding food security and stimulates the local economy through subsistence and recreational fishing. However, local fishers suggest that catch rates of H. vittatus have declined and the fish are now smaller. The Namibian Ministry of Fisheries and Marine Resources conducted annual gill net surveys in the Kavango River from 1994 to 2018. These standardised surveys were used to compare catch per unit effort data and length frequencies of H. vittatus between intensively fished areas and a freshwater protected area (FPA). The catch per unit effort (by numbers and mass) and proportion (56% vs 10–20%) of mature fish (males >180 mm fork length and females >280 mm fork length) were higher inside the FPA, compared with those outside. The H. vittatus populations, both outside and inside the FPA, are subject to overfishing and management actions should be taken to secure this important fishery resource for subsistence and recreational fishers.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"207 - 215"},"PeriodicalIF":1.4,"publicationDate":"2022-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44754578","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 : 2022-03-17DOI: 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}
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