Pub Date : 2022-08-22DOI: 10.2989/16085914.2022.2093828
A. Birkhead, C. Brown, H. Bukhari, Mk Reinecke, W. Mgoola, JK Nyirenda
The Elephant Marsh lies on the floodplain of the lower Shire River, in southern Malawi. It is both a cultivated, seasonal floodplain and an area of permanent shallow lakes. The marsh is highly biodiverse, has a productive fishery and supports the livelihoods of a large human population. Chronicles and hand-drawn sketches by 19th-century explorers and subsequent travellers describing the marsh landscape were used to develop an account of the marsh’s historic hydromorphology. These anecdotal accounts are supported by Shire River outflows from Lake Malawi, inferred from observed water levels in the lake from c. 1900. Records show that the marsh has experienced regular periods of drying out, followed by periods of greater inundation than it currently experiences. Long-term hydrological trends have been accompanied by anthropogenic influences such as catchment degradation and embankment construction, which have altered sedimentation patterns in the marsh. The marsh exhibits traits of resilience to natural long-term climate change through its ability to return to a similar state during wet periods, even following prolonged dry periods. Over relatively short time frames, however, the ecology of the marsh, as described when it was declared a RAMSAR site in 2017, likely has low resistance to hydrological regimes that are sensitive to climate change. An appreciation of long-term climate and recent human-induced changes afforded a unique opportunity for contextualising its hydromorphological trends within the Anthropocene.
{"title":"The Elephant Marsh, Malawi – Part 1: reconstruction of the historic hydromorphology","authors":"A. Birkhead, C. Brown, H. Bukhari, Mk Reinecke, W. Mgoola, JK Nyirenda","doi":"10.2989/16085914.2022.2093828","DOIUrl":"https://doi.org/10.2989/16085914.2022.2093828","url":null,"abstract":"The Elephant Marsh lies on the floodplain of the lower Shire River, in southern Malawi. It is both a cultivated, seasonal floodplain and an area of permanent shallow lakes. The marsh is highly biodiverse, has a productive fishery and supports the livelihoods of a large human population. Chronicles and hand-drawn sketches by 19th-century explorers and subsequent travellers describing the marsh landscape were used to develop an account of the marsh’s historic hydromorphology. These anecdotal accounts are supported by Shire River outflows from Lake Malawi, inferred from observed water levels in the lake from c. 1900. Records show that the marsh has experienced regular periods of drying out, followed by periods of greater inundation than it currently experiences. Long-term hydrological trends have been accompanied by anthropogenic influences such as catchment degradation and embankment construction, which have altered sedimentation patterns in the marsh. The marsh exhibits traits of resilience to natural long-term climate change through its ability to return to a similar state during wet periods, even following prolonged dry periods. Over relatively short time frames, however, the ecology of the marsh, as described when it was declared a RAMSAR site in 2017, likely has low resistance to hydrological regimes that are sensitive to climate change. An appreciation of long-term climate and recent human-induced changes afforded a unique opportunity for contextualising its hydromorphological trends within the Anthropocene.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"369 - 385"},"PeriodicalIF":1.4,"publicationDate":"2022-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43574576","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 : 2022-08-05DOI: 10.2989/16085914.2022.2094323
M. Nunes, D. Lemley, J. Adams
Primary producer responses to cumulative regulating factors were investigated in a temporarily closed microtidal estuary. We hypothesised that the phytoplankton chlorophyll-a concentration (Chl a) and invasive alien aquatic plant (IAAP) abundance would be highest during the low-flow season and that shifts in community structure would be driven by salinity and nutrient gradients. The augmented freshwater inflow limited phytoplankton Chl a (<5 µg Chl a l−1) due to low freshwater residency, while isolated instances of increased Chl a (≥10 but ≤20 µg Chl a l−1) were recorded following a brief period of mouth closure. Cyanophyceae proliferated for 67% of the study period with maximum abundance (>10 000 cells ml−1) recorded in spring owing to increased water retention. A community consisting of co-dominant Cryptophyceae, Euglenophyceae and IAAPs was recorded during winter, indicating a shared preference for slow-flowing, low-salinity (<5) eutrophic habitats. Dinophyceae was the only phytoplankton class that showed niche differentiation by favouring the mesohaline lower reaches. The homogenisation of dynamic estuarine gradients and the prevalence of nutrient-tolerant primary producers is indicative of the degraded state of this estuary as a result of consistent nutrient-enriched freshwater baseflows. The application of a multidisciplinary restoration approach is required to improve the ecosystem health.
{"title":"Flow alterations and nutrient loading reduce primary producer variability in a temporarily closed microtidal estuary in KwaZulu-Natal, South Africa","authors":"M. Nunes, D. Lemley, J. Adams","doi":"10.2989/16085914.2022.2094323","DOIUrl":"https://doi.org/10.2989/16085914.2022.2094323","url":null,"abstract":"Primary producer responses to cumulative regulating factors were investigated in a temporarily closed microtidal estuary. We hypothesised that the phytoplankton chlorophyll-a concentration (Chl a) and invasive alien aquatic plant (IAAP) abundance would be highest during the low-flow season and that shifts in community structure would be driven by salinity and nutrient gradients. The augmented freshwater inflow limited phytoplankton Chl a (<5 µg Chl a l−1) due to low freshwater residency, while isolated instances of increased Chl a (≥10 but ≤20 µg Chl a l−1) were recorded following a brief period of mouth closure. Cyanophyceae proliferated for 67% of the study period with maximum abundance (>10 000 cells ml−1) recorded in spring owing to increased water retention. A community consisting of co-dominant Cryptophyceae, Euglenophyceae and IAAPs was recorded during winter, indicating a shared preference for slow-flowing, low-salinity (<5) eutrophic habitats. Dinophyceae was the only phytoplankton class that showed niche differentiation by favouring the mesohaline lower reaches. The homogenisation of dynamic estuarine gradients and the prevalence of nutrient-tolerant primary producers is indicative of the degraded state of this estuary as a result of consistent nutrient-enriched freshwater baseflows. The application of a multidisciplinary restoration approach is required to improve the ecosystem health.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"447 - 461"},"PeriodicalIF":1.4,"publicationDate":"2022-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49236606","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 : 2022-06-24DOI: 10.2989/16085914.2022.2080174
I. Onah, OJ Ajanwachukwu, PO Ubachukwu
The physico-chemical parameters of water provide crucial information on the condition of a waterbody at a point in time. Physico-chemical parameters determine the primary and secondary productivity of an aquatic ecosystem. Data on water temperature, pH, turbidity, water depth, total dissolved solids, total hardness, biochemical oxygen demand, dissolved oxygen, chloride, nitrate and phosphate, together with information on the aquatic macroinvertebrate and vertebrate species composition and abundance were collected for two Nigerian lakes, Lake Ogelube and Lake Ojii at Opi-Agu. The physico-chemical parameters were analysed using standard methods. Macroinvertebrate and vertebrate (Actinopterigii and Amphibia) species composition and abundance in the lakes were correlated with the physico-chemical parameters. Temperature, depth, biochemical oxygen demand and phosphate were significantly higher in Lake Ojii than in Lake Ogelube, while pH, turbidity and nitrate were significantly higher in Lake Ogelube (p < 0.05). In total, 1 442 animals were collected from the lakes of which 1 101 were macroinvertebrates and 341 vertebrates. The family Libellulidae (Order: Odonata) and the species Coptodon zillii (synonym: Tilapia zillii) (Gervais, 1848) (Perciformes: Cichlidae) were the most abundant macroinvertebrate and vertebrate taxa, respectively. Libellulidae were negatively associated with biochemical oxygen demand, temperature, turbidity, phosphate and chloride and Coptodon zillii was positively associated with dissolved oxygen.
{"title":"Comparison of physico-chemical parameters with macroinvertebrate and vertebrate fauna of Lake Ogelube and Lake Ojii, Opi-Agu, south-eastern Nigeria","authors":"I. Onah, OJ Ajanwachukwu, PO Ubachukwu","doi":"10.2989/16085914.2022.2080174","DOIUrl":"https://doi.org/10.2989/16085914.2022.2080174","url":null,"abstract":"The physico-chemical parameters of water provide crucial information on the condition of a waterbody at a point in time. Physico-chemical parameters determine the primary and secondary productivity of an aquatic ecosystem. Data on water temperature, pH, turbidity, water depth, total dissolved solids, total hardness, biochemical oxygen demand, dissolved oxygen, chloride, nitrate and phosphate, together with information on the aquatic macroinvertebrate and vertebrate species composition and abundance were collected for two Nigerian lakes, Lake Ogelube and Lake Ojii at Opi-Agu. The physico-chemical parameters were analysed using standard methods. Macroinvertebrate and vertebrate (Actinopterigii and Amphibia) species composition and abundance in the lakes were correlated with the physico-chemical parameters. Temperature, depth, biochemical oxygen demand and phosphate were significantly higher in Lake Ojii than in Lake Ogelube, while pH, turbidity and nitrate were significantly higher in Lake Ogelube (p < 0.05). In total, 1 442 animals were collected from the lakes of which 1 101 were macroinvertebrates and 341 vertebrates. The family Libellulidae (Order: Odonata) and the species Coptodon zillii (synonym: Tilapia zillii) (Gervais, 1848) (Perciformes: Cichlidae) were the most abundant macroinvertebrate and vertebrate taxa, respectively. Libellulidae were negatively associated with biochemical oxygen demand, temperature, turbidity, phosphate and chloride and Coptodon zillii was positively associated with dissolved oxygen.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"489 - 498"},"PeriodicalIF":1.4,"publicationDate":"2022-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47111559","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 : 2022-06-07DOI: 10.2989/16085914.2022.2047589
J. Ewart-Smith
In open-canopied temperate rivers, periphyton plays a pivotal role by converting dissolved nutrients into food for biota. International research suggests that periphyton is particularly responsive to flow and nutrient alterations and therefore ideally suited to aiding the prediction and monitoring of the effects of altered flow regimes. Given that one of South Africa’s key focus areas for river management has been the provision of flows to sustain aquatic ecosystems, this study aimed to quantify the relative importance of potential environmental drivers of periphyton, particularly flow, under different nutrient conditions in rivers of the south-western Cape. The study focused on two perennial rivers, the Berg and Molenaars Rivers. Quantitative monthly samples of periphyton biomass were collected from four sites, representative of different flow and nutrient regimes, over a 21-month sampling period between September 2007 and May 2009. The frequency of flood disturbance over the wet season was found to be the single most important driver of periphyton communities. It accounted for almost 75% of the total variation in periphyton biomass under natural flow and nutrient-poor conditions and it was therefore identified as the primary driver of periphyton communities. Its role was smaller under moderately enriched conditions and accounted for 45% of the total variation. These findings suggest that periphyton in south-western Cape rivers has great potential as a tool for predicting and monitoring the effects of altered flow regimes under different nutrient enrichment regimes. Together with some insight into community structure, the next step is to develop periphyton indicators that reflect different aspects of ecosystem integrity, for use in scenario modelling and other management aspects.
{"title":"Drivers of periphyton biomass in south-western Cape rivers, South Africa, and the implications for management","authors":"J. Ewart-Smith","doi":"10.2989/16085914.2022.2047589","DOIUrl":"https://doi.org/10.2989/16085914.2022.2047589","url":null,"abstract":"In open-canopied temperate rivers, periphyton plays a pivotal role by converting dissolved nutrients into food for biota. International research suggests that periphyton is particularly responsive to flow and nutrient alterations and therefore ideally suited to aiding the prediction and monitoring of the effects of altered flow regimes. Given that one of South Africa’s key focus areas for river management has been the provision of flows to sustain aquatic ecosystems, this study aimed to quantify the relative importance of potential environmental drivers of periphyton, particularly flow, under different nutrient conditions in rivers of the south-western Cape. The study focused on two perennial rivers, the Berg and Molenaars Rivers. Quantitative monthly samples of periphyton biomass were collected from four sites, representative of different flow and nutrient regimes, over a 21-month sampling period between September 2007 and May 2009. The frequency of flood disturbance over the wet season was found to be the single most important driver of periphyton communities. It accounted for almost 75% of the total variation in periphyton biomass under natural flow and nutrient-poor conditions and it was therefore identified as the primary driver of periphyton communities. Its role was smaller under moderately enriched conditions and accounted for 45% of the total variation. These findings suggest that periphyton in south-western Cape rivers has great potential as a tool for predicting and monitoring the effects of altered flow regimes under different nutrient enrichment regimes. Together with some insight into community structure, the next step is to develop periphyton indicators that reflect different aspects of ecosystem integrity, for use in scenario modelling and other management aspects.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"259 - 274"},"PeriodicalIF":1.4,"publicationDate":"2022-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47777642","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 : 2022-06-07DOI: 10.2989/16085914.2022.2067823
J. Wasserman, J. Adams, D. Lemley
Saltpans are increasingly being abandoned around the world, leading to the loss of ecosystem services provided by these unique semi-natural wetlands. The desertion of a saltpan at the Swartkops Estuary, South Africa has left behind a large area of desiccated hypersaline sediment and a sharp decrease in waterbird abundance and diversity. Here, we explore the potential for restoring this saltpan’s wetland function using stormwater inflow to support multiple ecosystem services and improve estuary health. Stormwater will be able to flow into the saltpan as a passive restoration approach that can maintain the site as a wetland habitat. This will contribute to improving the health of a nationally important, yet highly degraded, estuary by retaining 758 ML of stormwater to achieve full capacity, containing an estimated 2908 kg of dissolved inorganic nitrogen and 68 kg of dissolved inorganic nitrogen. Additional ecosystem services such as biodiversity maintenance, carbon storage and societal values can be expected. However, this would create a novel hypersaline stormwater wetland and a strategic adaptive management approach will be required. Management must be guided by monitoring, which should comprise collection of basic environmental data to establish a baseline condition, and against which, long term changes and responses resulting from stochastic events can be assessed and mitigated through the use of achievable ecological restoration targets.
{"title":"Investigating the potential for saltpan restoration for the provision of multiple ecosystem services","authors":"J. Wasserman, J. Adams, D. Lemley","doi":"10.2989/16085914.2022.2067823","DOIUrl":"https://doi.org/10.2989/16085914.2022.2067823","url":null,"abstract":"Saltpans are increasingly being abandoned around the world, leading to the loss of ecosystem services provided by these unique semi-natural wetlands. The desertion of a saltpan at the Swartkops Estuary, South Africa has left behind a large area of desiccated hypersaline sediment and a sharp decrease in waterbird abundance and diversity. Here, we explore the potential for restoring this saltpan’s wetland function using stormwater inflow to support multiple ecosystem services and improve estuary health. Stormwater will be able to flow into the saltpan as a passive restoration approach that can maintain the site as a wetland habitat. This will contribute to improving the health of a nationally important, yet highly degraded, estuary by retaining 758 ML of stormwater to achieve full capacity, containing an estimated 2908 kg of dissolved inorganic nitrogen and 68 kg of dissolved inorganic nitrogen. Additional ecosystem services such as biodiversity maintenance, carbon storage and societal values can be expected. However, this would create a novel hypersaline stormwater wetland and a strategic adaptive management approach will be required. Management must be guided by monitoring, which should comprise collection of basic environmental data to establish a baseline condition, and against which, long term changes and responses resulting from stochastic events can be assessed and mitigated through the use of achievable ecological restoration targets.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"436 - 446"},"PeriodicalIF":1.4,"publicationDate":"2022-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45765111","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 : 2022-05-10DOI: 10.2989/16085914.2022.2047590
O. N. Odume
Freshwater is one of the Earth’s most crucial resources for social-economic development and prosperity. Biomonitoring contributes to water resource protection by integrating a holistic picture of ecosystem health through an analysis of resident biota. The taxonomy-based approach, in which taxa assemblages are analysed and compared between sites, is common in freshwater biomonitoring. However, this approach is mainly descriptive and has no predictive or effect diagnostic potential. The trait-based approach (TBA) has been hailed as capable of transforming biomonitoring into a predictive science with the potential for effect diagnosis. This paper presents a framework for the potential use of traits in riverine water resource monitoring and management. It provided ways to integrate the TBA into the Resource Quality Objectives (RQOs), current biomonitoring protocols, and developing predictive models. Their effect diagnostic potential, assemblage response predictive value and links to crucial ecosystem functions should guide the selection and integration of traits into RQOs. Examples of trait-based RQOs statements are provided.
{"title":"The contribution and value of the trait-based approach to water resource protection","authors":"O. N. Odume","doi":"10.2989/16085914.2022.2047590","DOIUrl":"https://doi.org/10.2989/16085914.2022.2047590","url":null,"abstract":"Freshwater is one of the Earth’s most crucial resources for social-economic development and prosperity. Biomonitoring contributes to water resource protection by integrating a holistic picture of ecosystem health through an analysis of resident biota. The taxonomy-based approach, in which taxa assemblages are analysed and compared between sites, is common in freshwater biomonitoring. However, this approach is mainly descriptive and has no predictive or effect diagnostic potential. The trait-based approach (TBA) has been hailed as capable of transforming biomonitoring into a predictive science with the potential for effect diagnosis. This paper presents a framework for the potential use of traits in riverine water resource monitoring and management. It provided ways to integrate the TBA into the Resource Quality Objectives (RQOs), current biomonitoring protocols, and developing predictive models. Their effect diagnostic potential, assemblage response predictive value and links to crucial ecosystem functions should guide the selection and integration of traits into RQOs. Examples of trait-based RQOs statements are provided.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"307 - 317"},"PeriodicalIF":1.4,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48768689","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 : 2022-04-04DOI: 10.2989/16085914.2022.2044750
C. Brown, A. Joubert, J. Turpie, K. Reinecke, A. Birkhead, K. Forsythe, T. Davies, W. Mgoola, J. Nyirenda, R. Arthur
In 2016, an application was prepared by the Malawian government for the Elephant Marsh on the Shire River to be granted RAMSAR status. As part of the support for that application and to help guide the resulting management plan, the eco-social holistic environmental flow assessment model DRIFT was set up for the Marsh. The aim was to predict the response of the Marsh to scenarios of changing water and sediment inflows, and to different levels of harvesting of its natural resources, in order to identify threats to and viable options for sustaining its biodiversity. The results of the DRIFT assessment provided three main points of guidance for the RAMSAR application and the subsequent development of a management plan. First, it was shown the Marsh has been fairly resilient to short-term changes in the inflows of water and sediments, having endured significant fluctuations in both in its history, and was able to recover in terms of biodiversity from extreme dry periods. Second, it was revealed that conservation efforts to protect biodiversity should concentrate on the central, eastern and southern areas, as they were less vulnerable to decreases in water flows than the other areas of the Marsh. Third, restricting access to some parts of the Marsh, in particular the core eastern, central and southern areas, could markedly improve its overall condition, increase many of its resources and improve its resilience to Climate Change. Of the access restrictions assessed, the greatest benefit to the ecological integrity of the Marsh would be achieved if all access to the central area was stopped, and if access to the eastern and southern areas was reduced to 50% of the 2014 baseline levels.
{"title":"The Elephant Marsh, Malawi – Part 3: the application of an eco-social model to assess options for managing ecological status","authors":"C. Brown, A. Joubert, J. Turpie, K. Reinecke, A. Birkhead, K. Forsythe, T. Davies, W. Mgoola, J. Nyirenda, R. Arthur","doi":"10.2989/16085914.2022.2044750","DOIUrl":"https://doi.org/10.2989/16085914.2022.2044750","url":null,"abstract":"In 2016, an application was prepared by the Malawian government for the Elephant Marsh on the Shire River to be granted RAMSAR status. As part of the support for that application and to help guide the resulting management plan, the eco-social holistic environmental flow assessment model DRIFT was set up for the Marsh. The aim was to predict the response of the Marsh to scenarios of changing water and sediment inflows, and to different levels of harvesting of its natural resources, in order to identify threats to and viable options for sustaining its biodiversity. The results of the DRIFT assessment provided three main points of guidance for the RAMSAR application and the subsequent development of a management plan. First, it was shown the Marsh has been fairly resilient to short-term changes in the inflows of water and sediments, having endured significant fluctuations in both in its history, and was able to recover in terms of biodiversity from extreme dry periods. Second, it was revealed that conservation efforts to protect biodiversity should concentrate on the central, eastern and southern areas, as they were less vulnerable to decreases in water flows than the other areas of the Marsh. Third, restricting access to some parts of the Marsh, in particular the core eastern, central and southern areas, could markedly improve its overall condition, increase many of its resources and improve its resilience to Climate Change. Of the access restrictions assessed, the greatest benefit to the ecological integrity of the Marsh would be achieved if all access to the central area was stopped, and if access to the eastern and southern areas was reduced to 50% of the 2014 baseline levels.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"405 - 420"},"PeriodicalIF":1.4,"publicationDate":"2022-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43445794","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: 10.2989/16085914.2022.2041388
L. van Niekerk, S. Taljaard, S. Lamberth, J. Adams, S. Weerts, C. MacKay
Globally, the ability of estuaries to sustain functionality and productivity is deteriorating rapidly under ever-increasing anthropogenic pressures. We present a systematic approach to identify, characterise and rank global pressures affecting estuaries. Six main pressure categories are reviewed: freshwater flow modification; pollution; exploitation of fish and invertebrates; land-use and development; manipulation of inlets; and biological invasions (plants and fish). Patterns in pressure effects are evaluated across biogeographic regions and estuary types. Activities contributing to these pressures are identified to prioritise management interventions and assessments of the trajectories of change and data availability are estimated, with associated confidence ratings on these. Approximately 15% of national estuarine area is under severe flow modification pressure. Land-use and development result in severe pressures on 40% of the area. Approximately 15% of inlets are artificially manipulated, which affects 60% of estuarine area. Pollution places 34% of the area under severe pressure and 78% of the area is severely impacted by overfishing. Invasive terrestrial vegetation has infested a third of South African estuaries, and aquatic invasive plant species occur in at least 8% of estuaries. Alien or extralimital (translocated) fish cause severe pressure in 35% of the estuaries. Management responses to mitigate these impacts are recommended for systems under severe pressure and future research directions are identified.
{"title":"Disaggregation and assessment of estuarine pressures at the country-level to better inform management and resource protection – the South African experience","authors":"L. van Niekerk, S. Taljaard, S. Lamberth, J. Adams, S. Weerts, C. MacKay","doi":"10.2989/16085914.2022.2041388","DOIUrl":"https://doi.org/10.2989/16085914.2022.2041388","url":null,"abstract":"Globally, the ability of estuaries to sustain functionality and productivity is deteriorating rapidly under ever-increasing anthropogenic pressures. We present a systematic approach to identify, characterise and rank global pressures affecting estuaries. Six main pressure categories are reviewed: freshwater flow modification; pollution; exploitation of fish and invertebrates; land-use and development; manipulation of inlets; and biological invasions (plants and fish). Patterns in pressure effects are evaluated across biogeographic regions and estuary types. Activities contributing to these pressures are identified to prioritise management interventions and assessments of the trajectories of change and data availability are estimated, with associated confidence ratings on these. Approximately 15% of national estuarine area is under severe flow modification pressure. Land-use and development result in severe pressures on 40% of the area. Approximately 15% of inlets are artificially manipulated, which affects 60% of estuarine area. Pollution places 34% of the area under severe pressure and 78% of the area is severely impacted by overfishing. Invasive terrestrial vegetation has infested a third of South African estuaries, and aquatic invasive plant species occur in at least 8% of estuaries. Alien or extralimital (translocated) fish cause severe pressure in 35% of the estuaries. Management responses to mitigate these impacts are recommended for systems under severe pressure and future research directions are identified.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"127 - 148"},"PeriodicalIF":1.4,"publicationDate":"2022-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44793008","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: 10.2989/16085914.2022.2051423
Atuhombye Sigala, K. Ngongolo, N. Mmbaga
Freshwater habitats in Africa receive large amounts of pollutants that affect several aspects of aquatic biodiversity, including Kihansi spray toads (KST) (Nectophrynoides asperginis). Little information is available on the influence of anthropogenic activities on the water quality along the Kihansi River, which is the only known habitat for this species. This study focused on assessing water quality and associated changes along the Kihansi River gradient where toads are being reintroduced following their recent extinction in the wild. Water samples for testing the pH, turbidity, dissolved oxygen (DO), temperature, total dissolved solids (TDS), and conductivity were collected from the upper, middle, and lower zones. In addition, socio-economic data were collected from three villages, namely Udagaji, Mgugwe and Ukami, which cover the river zone. The population trend of KSTs in captivity was obtained from the Kihansi Captive Facility (KCF). Cultivation of crops, such as rice and maize is the dominant socio-economic activity. Temperature, pH, and DO showed significant variation among the three sampled zones (p < 0.05). Crop cultivation and agroforestry practices near the river significantly increased the pH and TDS, while reducing the DO in the water. The toads in captivity increased in number significantly by 12.77% (n = 1 410). Anthropogenic activities, such as agriculture, agroforestry and grazing affect water quality, and proper management of the Kihansi River requires the involvement of local communities to ensure the survival of the reintroduced KST.
{"title":"Influence of anthropogenic activities on water quality of the Kihansi River (Tanzania) and on population trends of captive Kihansi spray toads (Nectophrynoides asperginis)","authors":"Atuhombye Sigala, K. Ngongolo, N. Mmbaga","doi":"10.2989/16085914.2022.2051423","DOIUrl":"https://doi.org/10.2989/16085914.2022.2051423","url":null,"abstract":"Freshwater habitats in Africa receive large amounts of pollutants that affect several aspects of aquatic biodiversity, including Kihansi spray toads (KST) (Nectophrynoides asperginis). Little information is available on the influence of anthropogenic activities on the water quality along the Kihansi River, which is the only known habitat for this species. This study focused on assessing water quality and associated changes along the Kihansi River gradient where toads are being reintroduced following their recent extinction in the wild. Water samples for testing the pH, turbidity, dissolved oxygen (DO), temperature, total dissolved solids (TDS), and conductivity were collected from the upper, middle, and lower zones. In addition, socio-economic data were collected from three villages, namely Udagaji, Mgugwe and Ukami, which cover the river zone. The population trend of KSTs in captivity was obtained from the Kihansi Captive Facility (KCF). Cultivation of crops, such as rice and maize is the dominant socio-economic activity. Temperature, pH, and DO showed significant variation among the three sampled zones (p < 0.05). Crop cultivation and agroforestry practices near the river significantly increased the pH and TDS, while reducing the DO in the water. The toads in captivity increased in number significantly by 12.77% (n = 1 410). Anthropogenic activities, such as agriculture, agroforestry and grazing affect water quality, and proper management of the Kihansi River requires the involvement of local communities to ensure the survival of the reintroduced KST.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"216 - 223"},"PeriodicalIF":1.4,"publicationDate":"2022-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42970713","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: 10.2989/16085914.2022.2044748
M. Zvavahera, S. Hugo, N. Vine, O. Weyl
South Africa lacks research on the nutritional value of inland small fish species available to poor rural communities, despite the potential of such species to mitigate micronutrient deficiencies. Here we provide the first nutrient composition analysis for estuarine roundherring Gilchristella aestuaria, a widespread small fish species that is abundant in many estuarine and freshwater habitats. Protein, fat, calcium, iron, zinc and vitamin A content of G. aestuaria from five estuarine and two freshwater habitats were analysed. We found no difference in nutrient content between estuarine and freshwater habitats, and no significant correlation (Spearman’s test) between levels of each nutrient and variation in temperature, turbidity, pH, chlorophyll a, phosphates, nitrates and ammonia. Compared with other small fish species consumed in other countries, G. aestuaria has comparable iron, zinc, calcium, fat and protein, but very low levels of vitamin A. When considering the recommended dietary allowance of infants aged two or more, adult men and women, and pregnant and lactating women, we found that G. aestuaria is an excellent source of all these nutrients, except vitamin A.
{"title":"Macro- and micronutrient composition of estuarine roundherring (Gilchristella aestuaria) (Pisces: Clupeidae) in the Eastern Cape, South Africa: a potential dietary source of essential nutrients","authors":"M. Zvavahera, S. Hugo, N. Vine, O. Weyl","doi":"10.2989/16085914.2022.2044748","DOIUrl":"https://doi.org/10.2989/16085914.2022.2044748","url":null,"abstract":"South Africa lacks research on the nutritional value of inland small fish species available to poor rural communities, despite the potential of such species to mitigate micronutrient deficiencies. Here we provide the first nutrient composition analysis for estuarine roundherring Gilchristella aestuaria, a widespread small fish species that is abundant in many estuarine and freshwater habitats. Protein, fat, calcium, iron, zinc and vitamin A content of G. aestuaria from five estuarine and two freshwater habitats were analysed. We found no difference in nutrient content between estuarine and freshwater habitats, and no significant correlation (Spearman’s test) between levels of each nutrient and variation in temperature, turbidity, pH, chlorophyll a, phosphates, nitrates and ammonia. Compared with other small fish species consumed in other countries, G. aestuaria has comparable iron, zinc, calcium, fat and protein, but very low levels of vitamin A. When considering the recommended dietary allowance of infants aged two or more, adult men and women, and pregnant and lactating women, we found that G. aestuaria is an excellent source of all these nutrients, except vitamin A.","PeriodicalId":7864,"journal":{"name":"African Journal of Aquatic Science","volume":"47 1","pages":"224 - 229"},"PeriodicalIF":1.4,"publicationDate":"2022-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45506282","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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