Johan HJ van Vuren

Johan HJ van Vuren
University of Johannesburg | uj · Department of Zoology

Doctor of Philosophy

About

151
Publications
28,929
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Introduction

Publications

Publications (151)
Article
Full-text available
A need exists to understand how drought and its linked consequences threaten aquatic ecosystems and their associated biota in semi-arid countries, as climate change is predicted to increase the effects of these events. South Africa experienced one of the worst droughts in its history from 2015 to 2017 and, as a result, all but the permanent waterbo...
Article
Full-text available
Climate induced drought is a prominent threat to natural saline aquatic ecosystems by modifying their hydrology and salinity, which impacts the biodiversity of these ecosystems. Lake Nyamithi is a naturally saline lake in South Africa that experienced the effects of a two-year supra-seasonal drought (2015–2016). This study aimed to determine potent...
Article
Southern Africa has one of the highest densities of temporary pools and some of the most understudied temporary wetlands in the world. Additionally, the eastern African annual killifishes (Nothobranchius spp.) are rare in southern Africa and found exclusively in temporary habitats. There is a notable lack of literature regarding the diet of these f...
Article
Full-text available
Biomarkers are applied as early warning indicators of organisms' exposure to pollutants. The aim of this study was to utilise a multi-biomarker approach in the freshwater shrimp Caridina nilotica (Decapoda: Atyidae) as indicators of persistent pollutant exposure. A suite of biomarkers was selected to cover oxidative stress and damage, and energetic...
Article
Full-text available
Floodplain ecosystems in Africa are under threat due to direct anthropogenic pressure and climate change. The lower Phongolo River and associated floodplain is South Africa's largest inland floodplain ecosystem and has been regulated by the Pongolapoort Dam since the 1970s. The last controlled flood release from the dam occurred in December 2014, a...
Article
Vanadium is a metal whose toxicity towards terrestrial and aquatic species has been under-reported to date. The biochemical responses of vanadium in amphibian species have not been determined. To establish the effects of vanadium (V) on exposed adult Xenopus laevis, acute and chronic exposures were conducted, and biomarker analyses were performed o...
Article
Dichlorodiphenyltrichloroethane (DDT) is an organochlorine insecticide that has been used for indoor residual spraying for the control of mosquito-borne diseases including malaria. However, due to its toxicity and environmental persistence, there are concerns about its potential deleterious effects in humans and wildlife. Therefore, the current stu...
Article
The Phongolo River floodplain (PRF) is an ecologically important area and surrounded by rural communities reliant on its aquatic resources, including fishes for subsistence fisheries. Although rural in nature, these aquatic systems are under anthropogenic pressures, including, several persistent organochlorine pesticides (OCP) such as DDT, currentl...
Article
The use of 1,1′-(2,2,2-Trichloro-1,1-ethanediyl)bis(4-chlorobenzene) (DDT) as a pesticide for the control of insects vectors responsible for the spread of many life threatening diseases was officially banned in 1972 by the United States Environmental Protection Agency (USEPA). It was banned throughout the world, in most developed countries, because...
Article
Full-text available
Depression wetlands (colloquially referred to in South Africa (SA) as pans) are found worldwide and primarily occur in arid regions including North and South America, southern and central Africa and southern and western Australia. Surface water resources in SA, and specifically in Gauteng, are under pressure from urbanisation, poor agricultural pra...
Article
Full-text available
The objective of this study was to identify potential mRNA expression changes in chicken livers associated with environmental exposure to dichloro-diphenyl-trichloroethane (DDT) and its metabolites (DDTs). In particular, we focused on genes relating to the immune system and metabolism. We analyzed liver samples from free-ranging chickens in KwaZulu...
Article
Full-text available
Many biotic integrity indices are not able to isolate community effects due to pesticide exposure as the communities also respond to other anthropogenic and natural stressors. A macroinvertebrate trait bioindicator system that is pesticide specific was therefore developed to overcome these challenges. This system, called SPEAR (SPEcies At Risk), wa...
Article
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Many countries with incidence of malaria, including those surrounding Maputo Bay, use dichloro-diphenyl-trichloroethane (DDT) to reduce mosquitoes. This study is the first to estimate the human health risk associated with consumption of marine fish from Maputo Bay contaminated with DDTs. The median for ∑DDTs was 3.8 ng/g ww (maximum 280.9 ng/g ww)....
Article
Studies have shown high levels of contamination of both metals and organochlorine pesticides (OCPs) in aquatic systems of the world renowned Kruger National Park, South Africa. With effects evident in top predators, including, unexplained Crocodylus niloticus deaths and organ level and histological changes in Hydrocynus vittatus. A suite of biomark...
Article
Full-text available
This study investigated the use of an exotic fish species Oreochromis niloticus as a bio-indicator organism in active biomonitoring of Yellow Jacket and Mazowe rivers, Zimbabwe, receiving acid mine drainage from Iron Duke Mine. The Yellow Jacket River flows through Iron Duke Pyrite Mine while the Mazowe River passes through the Mazowe factory and e...
Article
Full-text available
Ethiopia and South Africa are among the few countries to still implement indoor residual spraying with dichloro-diphenyl-trichloroethane (DDT) for malaria vector control. In this study, we investigated the levels and ecological risks of DDT and its metabolites in liver tissues of house rat, as a sentinel animal, for providing an early warning syste...
Article
Organochlorine pesticides such as dichlorodiphenyltrichloroethane (DDT) have been used in agriculture and for disease control purposes over many decades. Reports suggest that DDT exposure may result in a number of adverse effects in humans. In the KwaZulu-Natal Province of South Africa, DDT is sprayed annually in homes (indoor residual spraying) to...
Article
Full-text available
The Phongolo floodplain in South Africa is a unique system because of its biodiversity and socio-economic value. The spatial and temporal changes of invertebrate communities of the downstream floodplain influenced by controlled flooding from an upstream dam are poorly understood. The study investigated the spatial and temporal changes in community...
Poster
Full-text available
The KNP is a leading conservation area found along South Africa’s eastern border. With a responsibility toward maintaining vital ecological processes and life support systems by ensuring the preservation of genetic diversity and utilization of species and ecosystems. The water supply of the KNP is dependent upon seven major rivers subjected to num...
Poster
Full-text available
There is a need for sensitive bio-monitoring and indicator tools in toxicant impact assessment to show the effect of toxicants on fish health in polluted aquatic ecosystems. Histopathological and biomarker assessments of fish tissue are a bio-monitoring tool and allows for early warning signs of disease and detection of long term injury in cells, t...
Article
Large scale irrigation schemes are vitally important for food security in developing countries. This is especially relevant in subtropical countries where there is pressure on their water resources. However, the potential impacts on the fish communities of the rivers associated with these irrigation systems are extensive and potentially devastating...
Conference Paper
Full-text available
The Ndumo Game Reserve protects a portion of the ecologically important and sensitive Phongolo River floodplain. An accredited Ramsar site, the reserve seeks to protect the floodplain and mitigate possible impacts to ecosystem functioning. However, aquatic systems are dynamic, and pollutants from upstream of the reserve enter the protected area and...
Conference Paper
The Phongolo floodplain in South Africa is a unique system because of its biodiversity and socio-economic value. The effects of controlled flow on the invertebrate community structure by an upstream dam on this floodplain are poorly understood. This study investigated the effect of controlled flooding on macroinvertebrates and zooplankton community...
Article
Metals are known to have deleterious effects on aquatic ecosystems, so monitoring the bioaccumulation of these pollutants is important for the assessment of potential impacts. The aim of the study was therefore to determine the degree to which aquatic biota in selected rivers of the world renowned Kruger National Park (KNP) are exposed to metals en...
Book
Full-text available
The construction of the Pongolapoort Dam in the Phongolo River started in 1960 with the purpose to supply irrigation water for the proposed sugarcane and cotton plantations in the adjacent floodplain, the Makhathini flats. The floodplain of approximately 10 000 ha increases in size to 13 000 ha at full inundation. The floodplain extends to the conf...
Presentation
Lateral hydrological connectivity refers to the permanent or temporary links between the main river with wetlands in the floodplain. The degree of hydrological connectivity between the river and floodplain wetlands depends on their distance to the river. The concept of lateral connectivity has been studied extensively but little information is avai...
Article
Full-text available
Shallow wetlands, such as pans, are not well studied in South Africa, even though they perform many important functions, such as providing an important food source for migratory birds and habitat to highly specialized fauna. Aquatic invertebrate diversity, abundance, and water quality in pans were analysed seasonally from 3 provinces in South Afric...
Article
With the second highest gross domestic product in Africa, South Africa is known to have a high pesticide usage, including the highly persistent and banned group of organochlorine pesticides (OCPs). South Africa is also one of few countries to still actively spray DDT as malaria vector control. The aim of the study was to determine the degree to whi...
Article
There has been a recent increase in water quality problems in South Africa. The monitoring of water resources is important for the continued management of water resources. The use of artificial mussels(AMs) as passive sampling devices in the monitoring of metals within a freshwater system was evaluated in a recent field study. Correlation testing w...
Article
Shallow wetlands, such as pans, are not well studied in South Africa, even though they perform many important functions, such as providing an important food source for migratory birds and habitat to highly specialized fauna. Aquatic invertebrate diversity, abundance, and water quality in pans were analysed seasonally from 3 provinces in South Afric...
Article
Full-text available
The physical and chemical characteristics of surface sediments from a leading conservation area, namely the Kruger National Park, were determined in order to identify potential stressors in the systems that may contribute to overall deterioration in sediment quality within the reserve, leading to potential threats to the aquatic biota conserved wit...
Conference Paper
Full-text available
Vuren, J.H.J. 2015. HCH's in two fish species from a large floodplain pan within a subtropical conservation area. The use of fish as biological indicators of aquatic system health is a well-documented practice. This study was conducted in order to establish whether specific organochlorine pesticides (OCP) are present within the Nyamiti Pan, situate...
Article
The construction of Pongolapoort Dam in 1973 on the Phongolo River in KwaZulu-Natal, South Africa, has considerably altered the hydrological behaviour and ecological response of the downstream floodplain. Changes in the flooding regime have had implications for the socio-economic importance of the floodplain and for the structure and functioning of...
Article
Aquatic macroinvertebrates are rarely used in wetland assessments due to their variation. However, in terms of biodiversity, these invertebrates form an important component of wetland fauna. Spatial and temporal variation of macroinvertebrate assemblages in endorheic depressions (locally referred to as pans) in Mpumalanga and North West provinces w...
Conference Paper
Full-text available
Acid volatile sulphides (AVS) are believed to reduce the bioavailability of metals from sediments. The protective role of AVS in the metal contaminated Olifants River was studied by relating metal bioaccumulation in the Leaden mudfish, Labeo molybdinus, to different chemical characteristics of water and sediments from the same sites. The same level...
Conference Paper
Full-text available
Dichloro-diphenyl-trichloroethane (DDT) has been administered in indoor residual spraying as part of the KwaZulu-Natal Province’s malaria control program for several years. Toxicity of this pesticide has been demonstrated in many avian and mammalian species. For this study, meat was sampled from free-ranging chickens (n=25) reared for consumption w...
Conference Paper
Full-text available
The assessment and monitoring of persistent pesticides such as aldrin, endrin and dieldrin in aquatic ecosystems are important in order to determine their environmental fate and risks posed to aquatic biota. Hydrocynus vittatus were collected from sections of the Olifants, Letaba and Luvuvhu Rivers within the Kruger National Park, and analysed for...
Conference Paper
Full-text available
The Ndumo Game Reserve is situated in KwaZulu Natal, South Africa and is an area with uniquely high biodiversity. However like many protected areas, environmental contaminants entering from outside the conservation areas pose threats to the biota which are being protected. To establish the possible risks posed to the aquatic biota of the system, Ch...
Article
Aquatic macroinvertebrate community responses to the effects of various land uses were investigated in 2010-2013 in the Wilge River, a tributary of the Olifants River, South Africa. The catchment area is characterised by agricultural, mining and industrial activities, which potentially contribute to the river's deteriorating water quality and poor...
Article
Purpose The physical and chemical characteristics of sediment from a South African irrigation scheme were used to determine the sediment stressors within the system and to determine whether or not stressors have the potential to contribute to pollutant risk within the system. The information generated also strengthens the database of sediment chemi...
Article
Determining the composition of zooplankton in endorheic pans can be challenging, and live sampling of these microcrustaceans does not give a true indication of their species diversity and abundance. The incubation of zooplankton diapausing eggs can assist in determining their diversity and abundance. In this study the efficacy of two incubation met...
Article
Endorheic wetlands are abundant in South Africa, and are more commonly referred to as pans. The pan environment experiences daily and seasonal fluctuations in physico-chemical conditions, caused by variable hydroperiods. Branchiopod crustaceans are a unique group of fauna which are able to survive this variability through the production of dormant...
Technical Report
Full-text available
There is a large variability within the physico-chemical parameters of pans, and the selection of appropriate reference conditions can be complicated. Presently, classification systems are based mainly on pans in Mpumalanga province, where many are already affected by mining activities. The trophic state or salinity is not considered to be sufficie...
Article
Full-text available
A histology-based fish health assessment protocol was used in 2009–2010 to assess the health status of Clarias gariepinus from Pongolapoort Dam, South Africa. Nineteen fish were collected by angling. The histology of liver, kidney, gills and testes or ovaries was semi-quantitatively assessed and compared to that of fish from a reference site in the...
Book
Full-text available
Hydrocynus vittatus Castelnau, 1861, commonly known as tigerfish, is a flagship species widely distributed in the North Eastern region of South Africa, and are easily identified by the public. This species is actively targeted and utilised by angling and subsistence fishing communities and also used as indicator species by resource and water qualit...
Article
Full-text available
Perennial pans are a common feature of the Mpumalanga Highveld in South Africa and are increasingly under threat from mining and agricultural activities. Pans are endorheic wetlands that can be perennial or ephemeral in nature. They are widespread in arid and semi-arid regions throughout the world. Although phyllopod crustaceans dominate pan commun...
Article
Full-text available
The pesticide risk in agriculture in developing countries has not been adequately studied due to the extent and fate of pesticides in the environment often being unknown. South Africa is a country that has significant pressure on its freshwater and agricultural resources, which increases the possibility of pesticide effects. Thus, the aim of this s...
Article
Technical grade DDT is annually sprayed for malaria control in many under developed countries world wide. Despite the controversy surrounding the use of DDT, minimal research concerning the effects on indigenous fish species in these areas has been conducted. In this study, the objectives were to identify some of the effects of sprayed p,p'-DDT on...
Article
Full-text available
The Nyl River floodplain, a Ramsar site that provides habitat for a number of endangered species, is one of the jewels in the arid Limpopo province and thus its conservation and protection are vitally important. Very little work has been done on assessing its water quality and no data have been published on the metal concentrations found in this va...
Article
Full-text available
Pans are isolated, shallow depressions that are endorheic in nature. Because of the natural hydrological functioning of pans, these systems are usually restricted to arid regions and complete desiccation occurs seasonally. In the eastern provinces of South Africa many pans are perennial in nature often remaining inundated for several years. A study...
Article
Pans are isolated, shallow depressions that are endorheic in nature. Because of the natural hydrological functioning of pans, these systems are usually restricted to arid regions and complete desiccation occurs seasonally. In the eastern provinces of South Africa many pans are perennial in nature often remaining inundated for several years. A study...
Article
Full-text available
The use of exfoliative cytology as a bio-assessment tool was evaluated to (1) identify and describe different cell types of normal liver cytology of Oreochromis mossambicus, (2) identify and describe changes in the cell types after exposure to cadmium and zinc, and (3) determine if non-imaging-guided fine-needle aspiration (FNA) cytology can be per...