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The study assessed the impact of water and sediment quality on benthic macroinvertebrate assemblages in the Dwars River, a tributary of the Olifants River, Limpopo province, South Africa. Physico-c... more...

Many elements become toxic when they exceed certain concentrations in the environment. In the aquatic ecosystems, they can be accumulated in the biota such as fish and may be toxic to humans upon consumption. This study assessed bioaccumulation of the following elements; arsenic, cadmium, chromium, copper, lead and Zinc in the muscle tissue of ten common consumable fish species from Groot Letaba River in South Africa and assessed the potential human health risks. In the water, only zinc exceeded the recommended safe limit. However, most of the elements were found to be significantly accumulated in the sediments and the muscle tissue of the fish species. The elements were more accumulated in the omnivorous and some predatory fish species than the herbivores. Concentrations of As, Cd, Cr and Zn in the fish muscle tissue were above the recommended food safety guideline values, indicating a potential health risk to consumers, especially As at Site 1 and Zn at Site 4. There is a need therefore for continuous monitoring of trace metals and metalloids in the river in order to ensure the safety of aquatic organisms and humans who rely on the river. more...

The Ga-Selati River is subjected to different forms of pollution from mining, industrial and agricultural activities, and human settlements. The objectives of the study were to assess heavy metal pollution and to determine possible sources of pollutants in the river. Water and sediment samples were collected and analysed for the following selected metals: arsenic (As), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni) and zinc (Zn) using sequential Inductively Coupled Plasma-optical emission spectrometry (ICP-OES). The enrichment factor (EF) and geo-accumulation index (Igeo) were used to determine the level of metal pollution in the sediment. The results indicated that Cr and Ni were the most accumulated elements in the sediments, and the midstream sites (S4 and S5) showed a much higher pollution level than the upstream and downstream sites. The main sources of pollutants were mining, wastewater/sewage and agricultural discharges. This may pose a serious threat to the river and health risk to the nearby rural communities, which rely on the river, especially for drinking water. Proper management strategies to reduce pollution is therefore necessary. more...

Benthic macroinvertebrates and sediments can act as good indicators of environmental quality. The aim of this study was to assess the accumulation of chemical elements in the Gomphidae (Odonata) collected in the Blyde River. Seven sites were sampled for river sediments assessment and five sites for larvae (naiads) of Gomphidae bioaccumulation analysis. The tissue samples were analysed using inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed high levels of all of the tested elements except Cd in the sediment. The mean concentrations of As, Cu and Cr exceeded the standard guideline values, whereas Pb and Zn were below the standard guideline values. In the insect body tissue, the concentrations of most elements were higher than in the sediments. The elements with the highest concentrations were Mn, Zn, Cu, and As. The bioaccumulation factor (BF) showed a tendency for bioaccumulation for almost all of the selected elements in the insect. The BF value was high for Cu, Mn, Sb, and Zn (BF > 1). The high concentrations of elements in the insect body tissue may pose a risk to fish that consume them, and subsequently to humans when fish from the river are consumed. It is therefore important to monitor the river to reduce pollution to prevent health risks in humans, especially in communities that rely on the river for water and food. more...

The Ga-Selati River has been systemically impaired by increasing human activities in its catchment, resulting in contamination by mining, industrial and agricultural effluents and domestic waste, and as a result significantly impacting the water quality of the river. The study aimed at investigating the ecological state of the Ga-Selati River and the impact of water quality on the aquatic macroinvertebrate communities was conducted in 2014 and 2015. Five sites along the Ga-Selati River were selected for sampling macroinvertebrates. The family composition, based on abundance and diversity, was evaluated in relation to environmental variables. The levels of dissolved oxygen, conductivity, total dissolved solids, turbidity and nutrients affected the distribution of tolerant taxa. The number and diversity of macroinvertebrates were found to be higher at less degraded upstream sites compared to more degraded downstream sites. A canonical analysis clearly grouped the various macroinvertebrates with the physico-... more...

The Steelpoort River is affected by a wide range of pollutants resulting from mining, industrial and agricultural activities and domestic sewage. Benthic macroinvertebrates are often used to assess water quality as they respond to changes in the aquatic environment. The study was to assess the benthic macroinvertebrate communities in the Steelpoort River along a pollution gradient, from less polluted upstream to highly polluted downstream. The impacted downstream sites generally had the highest turbidity, total dissolved solids (TDS) and conductivity values but lowest dissolved oxygen. While the upstream sites generally exhibited low turbidity, TDS and conductivity values but high dissolved oxygen. The physical and chemical changes between sites were accompanied by shifts in macroinvertebrate community composition. The sensitive macroinvertebrate families such as Baetidae, Leptophlebiidae and Perlidae dominated the upstream sites with low water turbidity, low conductivity, low TDS, and high dissolved oxygen while the tolerant families such as Chironomidae, were abundant in highly impacted downstream sites with high water turbidity, high conductivity, high TDS, and low dissolved oxygen. The study revealed differences in physico-chemical parameters, and in the composition of the macroinvertebrate community. Hence, changes in the abundance and diversity of macroinvertebrates reflected the longitudinal pollution gradient in the river. more...

Steelpoort River has been adversely affected by human activities in the catchment. Water and sediment quality of the river was assessed in 2015. The concentrations of some of the metals in water were found to be high and exceeded the guideline values and the concentrations of metals in sediment were found exceeding the guideline values for Cr, Cu and Zn. The high concentrations of Cu and Zn at Site 1 and Site 2 (upstream) could have originated from anthropogenic sources, such as fertilisers and pesticides from discharge of agricultural wastes, whereas the high concentrations of Cr at Site 3, Site 4 (midstream) and Site 5 (downstream) could have originated from the mine waste, and from domestic/ industrial wastes respectively. The principal component analysis results showed two main components: PC-1 with high positive loading of Cu and Mn, and PC-2 with high positive loading of Zn. These findings indicate the presence of pollution. Therefore, control measures should be implemented to reduce river contamination from anthropogenic sources.Keywords: anthropogenic sources, fertilisers, pesticides, pollution, principal component analysis more...

Knowledge of the life cycle of Hemijana variegata is important for sustainable utilization of this edible insect. The fecundity and survival of H. variegata were investigated under ambient conditions in the laboratory. Eggs were laid in clutches of between 180 and 490 eggs per clutch, and took an average of 8.45 days to hatch. Hemijana variegata has five larval instars. The first-instar larvae are unable to feed on older leaves, thus survival of the larvae requires that hatching be synchronized with leaf emergence of the host plant in the field. The duration of the pupal stage varied between 32 days and more than 119 days. This wide variation may be an adaptation to annual climatic fluctuations such as years with no rain or late rainfall. This strategy might ensure their survival in areas where droughts are often experienced. The larvae had the highest mortality rate, followed by the pupae and then the eggs, with survivorship rates of 30.12 % (larvae), 63.98 % (pupae) and 98.67 % (eggs). Pupal survivorship could be higher, as 24 % of the pupae had not emerged after two years when the experiment was terminated. more...

Many impoverished rural communities rely on fish from inland waters for dietary protein; however, inland waters are becoming increasingly contaminated due to anthropogenic activities. The Olifants River is one of the most polluted river in South Africa. The upper catchment is characterized by acid mine drainage and elevated levels of contaminants from domestic, agricultural, industrial, and mining effluents. A human health risk assessment was conducted to determine whether 2 catfish species from 2 impoundments in the Olifants River were safe for human consumption. The concentrations of metal in the fish muscle were in most cases higher at Lake Flag Boshielo than at the downstream Phalaborwa Barrage. Consumption of catfish from Lake Flag Boshielo on a weekly basis could result in adverse health impacts from antimony, chromium, cobalt, and lead. For the Phalaborwa Barrage, only lead would be likely to pose a health risk for consumption of catfish at weekly frequency. more...

The present study describes total mercury (THg) levels in surface water, sediment and biota from the Olifants River Basin (ORB) (South Africa) and investigates the trophic transfer of THg by means of trophic magnification factors (TMFs) in the subtropical ORB food web. Although levels in surface water, sediment and invertebrates were low, elevated levels of THg were measured in fish species of higher trophic levels (0.10–6.1 μg/g dw). This finding supports the biomagnificative character of mercury. THg concentrations in fish from the present study were find to be higher than most values reported in fish from other African aquatic ecosystems and comparable or lower compared to more industrialized regions. Fish length, trophic level, sediment THg levels and TOC in sediment were determining factors for THg levels in fish tissue. Concentrations were found to be higher in larger (and older) fish. Mercury has a high affinity for organic matter and will bind with the TOC in sediment, thus reducing the bioavailability of THg for aquatic biota which is reflected in the significant negative correlation between THg and TOC in sediment. A significant positive relationship between relative trophic level and THg concentrations was observed and also TMFs indicate biomagnification in the ORB food web. However, the trend of lower TMFs in tropical areas compared to temperate and arctic regions was not supported by the results. The consumption of fish from higher trophic levels at the average South African consumption rate is expected to pose a significant health risk. more...

The Olifants River, Limpopo River system, is now one of the most polluted rivers in South Africa. The concentrations of metals in fish muscle tissue from two impoundments on the Olifants River, Flag Boshielo Dam and Phalaborwa Barrage, were measured and a human health risk assessment conducted to investigate whether it was safe to consume Labeo rosae from these impoundments. Labeo rosae is one of the most common pan-fish in these impoundments and is frequently available to rural communities. Metals are accumulating in the muscle tissue of L. rosae even though the populations appear to be healthy. At Flag Boshielo Dam the recommended hazard quotient (HQ) of 1 was exceeded for lead and chromium in all L. rosae analysed, and 53% exceeded that for antimony. At Phalaborwa Barrage almost all L. rosae analysed exceeded the recommended HQ for lead, and more...

Hemijana variegata Rothschild, an edible caterpillar of Limpopo, South Africa, is little known to science but is a delicacy in the region. Harvesters believe the caterpillar is nourishing but there are no data on its nutritional value. This study reports on the proximate nutrient analysis of sun-dried (traditionally prepared) specimens and specimens oven-dried at 60 °C for three different time periods (24, 48 and 72 h). For the vitamin content analysis, fresh caterpillars were used. Drying at 60 °C for 24 h produced the highest energy value at 552 kcal/100 g while traditionally prepared caterpillars produce 306 kcal/100 g. The caterpillar was found to be rich in protein varying between 51 and 54 % for oven-dried and 44.5 % for traditionally prepared caterpillars. The fat content of 20 % is favourable, as is the percentage ash (10.47 % for traditionally prepared caterpillars), indicating elevated levels of nutrients. In fresh caterpillars, vitamin content was low for vitamin A (0.02 mg/100 g) and vitamin B... more...

Rural communities in South Africa are becoming increasingly reliant on freshwater fish to supplement their dietary protein requirement. Rising costs of other protein sources, increasing rural poverty and escalating rural populations are resulting in increasing consumption of fish from contaminated river systems. The Olifants River, Limpopo Basin, Eastern South Africa, has been systemically impaired and is now one of the most polluted rivers in South Africa. We measured the concentrations of metals in fish muscle tissue from two impoundments in the Olifants River (Flag Boshielo Dam and the Phalaborwa Barrage) and conducted a human health risk assessment following Heath et al., (2004) to investigate whether consumption of Oreochromis mossambicus from these impoundments posed a risk to the health of rural communities. Our results show that metals are accumulating in the muscle tissue of O. mossambicus even though the populations appear to be healthy. No patterns were observed in the ratios of the metals accumulated in the muscle tissue of O. mossambicus at each impoundment. The human health risk assessment identified that lead, antimony and chromium at Flag Boshielo Dam and lead at the Phalaborwa Barrage were above acceptable levels for the safe consumption based on a weekly 150 g fish meal. We conclude that consuming O. mossambicus from these impoundments could pose an unacceptable risk to the health of rural communities. more...

This study investigates the trophic transfer of persistent organic pollutants (POPs: PCBs, PBDEs, OCPs and PFASs) in the subtropical aquatic ecosystem of the Olifants River Basin (South Africa) by means of trophic magnification factors (TMFs). Relative trophic levels were determined by stable isotope analysis. POP levels in surface water, sediment and biota were low. Only ∑ DDTs levels in fish muscle (< LOQ-61 ng/g ww) were comparable or higher than values from other temperate and tropical regions. Significant positive relationships between relative trophic level and PCB, DDT and HCH concentrations were observed so trophic levels play an important role in the movement of contaminants through the food web. TMFs were > 1, indicating biomagnification of all detected POPs. Calculated TMFs for PCBs were comparable to TMF values reported from the tropical Congo River basin and lower than TMFs from temperate and arctic regions. For p,p′-DDT, a higher TMF value was observed for the subtropical Olifants River during the winter low flow season than for the tropical Congo river. TMFs of DDTs from the present study were unexpectedly higher than TMFs from temperate and arctic aquatic food webs. The fish species in the aquatic ecosystem of the Olifants River can be consumed with a low risk for POP contamination. more...

We assessed the risk associated with introduction of sweet potato weevil, Cylas formicarius elegantulus (Summers) (Coleoptera: Brentidae), from infested areas to noninfested areas via shipment of sweet potato, Ipomoea batatas (L.), roots within the southern United States. Our study quantifies the effectiveness of risk mitigation procedures of sweet potatoes before shipment in relation to introduction of the weevil. The risk assessment relied on literature and expert information to determine appropriate parameters. Using a computational model, Monte Carlo simulations were conducted to estimate the likelihood of introduction of sweet potato weevil. Risk management options were incorporated and the risk analyses were performed to assess how the risk could be reduced. The study found the risk of introduction of the weevil for both domestic shipment and imports of sweet potatoes into new areas within the southern United States to be low. Sensitivity analysis was performed to assess model stability and the impact of parameter changes. Based on the sensitivity analysis, the most critical input was the postharvest mitigation, followed by the number of weevils per ton of sweet potatoes. We concluded that maintaining mitigations with monitoring in conjunction with public education to stop illegal transport of sweet potatoes and alternate hosts would significantly reduce the risk of introduction. more...

As rural populations grow and rural poverty increases, consumption of fish from contaminated river systems will increase to supplement dietary protein requirements. The concentrations of metals in fish muscle tissue at two impoundments of the Olifants River (Flag Boshielo Dam and the Phalaborwa Barrage) were measured, and a human health risk assessment following Heath et al. (2004) conducted to investigate whether consumption of Schilbe intermedius from these impoundments posed a risk to human health. The results confirmed that metals are accumulating in the muscle tissue of S. intermedius. No patterns were observed in the ratios of the metals bio-accumulated at each impoundment. The human health risk assessment identified that all fish analysed exceeded the recommended levels for safe consumption for lead and chromium and about 50% exceeded the recommended level for antimony at Flag Boshielo Dam. Almost all fish analysed exceeded the recommended level for lead and more than 50% exceeded the recommended level for arsenic at the Phalaborwa Barrage. We conclude that weekly consumption of S. intermedius from these impoundments may pose an unacceptable risk to the health of rural communities.Keywords: risk assessment, human health, Schilbe intermedius, lead, chromium, antimony more...

We assessed the risk associated with introduction of sweet potato weevil, Cylas formicarius elegantulus (Summers) (Coleoptera: Brentidae), from infested areas to noninfested areas via shipment of sweet potato, Ipomoea batatas (L.), roots within the southern United States. Our study quantifies the effectiveness of risk mitigation procedures of sweet potatoes before shipment in relation to introduction of the weevil. The risk assessment relied on literature and expert information to determine appropriate parameters. Using a computational model, Monte Carlo simulations were conducted to estimate the likelihood of introduction of sweet potato weevil. Risk management options were incorporated and the risk analyses were performed to assess how the risk could be reduced. The study found the risk of introduction of the weevil for both domestic shipment and imports of sweet potatoes into new areas within the southern United States to be low. Sensitivity analysis was performed to assess model stability and the impact of parameter changes. Based on the sensitivity analysis, the most critical input was the postharvest mitigation, followed by the number of weevils per ton of sweet potatoes. We concluded that maintaining mitigations with monitoring in conjunction with public education to stop illegal transport of sweet potatoes and alternate hosts would significantly reduce the risk of introduction. more...