5,779 research outputs found
South Africa
No full textSouth Africa has the second longest coastline on the African continent and spans two oceans. The confluence of the Benguela and Agulhas Currents off South Africa results in their dynamics being complex and often unpredictable, although it is these dynamic ocean systems that contribute to the high biodiversity and productivity of the South African coastal and marine ecosystems. There are 136 different habitat types ranging from subtropical coral reefs and mangroves on the north-east coast to temperate kelp forests and seamounts on the south and western coast. These habitats are under pressure from climate change as well as direct human impacts. Climate change is expected to influence the dynamic nature of the ocean systems through alterations of the currents, sea-level rise and increased water temperatures, ocean acidification, and storm events. Human activities such as fishing, overexploitation of marine resources, and coastal development have placed great pressures on marine and coastal habitats, biodiversity, and resources. Future threats include increased offshore mining activities in habitats that are not well studied or protected. Marine protection and management is achieved through the overarching National Environmental Management and Integrated Coastal Management Acts, which make provision for setting up marine protected areas (MPAs) and protection of individual species. Operation Phakisa is an exciting new initiative that has the potential to address the human resources capacity shortages, research requirements, and governance issues identified in this chapte
Adsorption, uptake and distribution of gold nanoparticles in Daphnia magna following long term exposure
No full textGold nanoparticles (nAu) have recently been studied and developed within the biological and photothermal therapeutic contexts. The major clinical interest is within the application of novel drug delivery systems. Environmental exposure to nanoparticles can occur in different stages of the lifecycle of the product; from their synthesis, applications, product weathering and their disposal. Freshwater Daphnids, specifically Daphnia magna, have been used since the 1960s as a standard species in acute and chronic aquatic toxicity testing. Visualization of the interactions and uptake of nAu by D. magna was related to reproduction and molting patterns. Exposure to nAu was done using a chronic reproduction test performed for 14 days at six concentrations (0.5 mg/L, 2 mg/L, 5 mg/L, 10 mg/L, 15 mg/L and 20 mg/L). Microscopy was used to determine whether there was any uptake or interaction of nAu with daphnia. However the concentration of nAu in the media and the charge of particles played a role in the uptake and surface adsorption. As exposure concentrations of nAu increased it appeared that the nAu aggregated onto the surface and in the gut of the organisms in higher concentrations. There was no evidence of nAu internalization into the body cavity of the daphnia. Aquatic exposure to nAu resulted in increased adhesion of the particles to the carapace of daphnia, ingestion and uptake into the gut of daphnia and had no significant effect on reproduction and molting pattern
Acute and chronic effects of acidic pH on four subtropical frog species
No full textAcidic precipitation is implicated as a possible cause of global amphibian decline. Even protected areas such as Kruger National Park receive acid rain which may lead to possible negative effects on the park’s natural amphibian populations. We conducted acute (LC50) and chronic acid tolerance bioassays on embryos and tadpoles of four frog species found in the park, i.e., Chiromantis xerampelina (Southern Foam Nest Frog), Pyxicephalus edulis (African Bullfrog), Amietophrynus maculatus (Flat-backed Toad) and Hildebrandtia ornata (Ornate Frog), using survival, deformities and growth as endpoints. Chronic exposure pH-values were selected based on the results of the acute assays. Trimmed Spearman-Karber LC50s were 4.07, 4.55, 3.75 and 3.747 for C. xerampelina, P. edulis, A. maculatus and H. ornata, respectively, and were all below the pHs in the natural ponds of the KNP. For chronic exposures tadpole size decreased and tadpole deformities increased with decreasing pH. Metamorphosis of tadpoles was also delayed by increasing acidity. In conclusion, the current buffering capacity of water bodies, which serve as habitat for amphibians, negates the effects of decreasing pH from acid precipitation.Keywords: low pH, acid precipitation, amphibians, mortality, developmental deformities, delayed metamorphosis, Kruger National Par
Distribution of perfluorinated compounds (PFASs) in the aquatic environment of the industrially polluted Vaal River, South Africa
No full textAbstract: Perfluorinated alkyl substances (PFASs) are highly persistent chemicals, which have a bioaccumulative potential and can be found in wildlife around the world. Although multiple studies have been performed on PFASs pollution of the aquatic environment, little is known on PFASs pollution on the African continent and their possible risks for human health. In the present study, we examined the distribution of 15 PFASs in fish, invertebrates, sediment and water, collected at three sites, representing a gradient of industrial and mining pollution, along the Vaal River, South Africa. Furthermore, possible risks for human health through consumption of contaminated fish were examined. Perfluorooctane sulfonate (PFOS) was the most dominant PFAS measured in biota, whereas perfluoropentanoic acid (PFPeA) was measured in higher concentrations in water. Mean PFAS concentrations in water ranged from <LOQ to 38.5 ng/L. PFAS concentrations in water decreased along the gradient and were similar or lower compared to other studies in Europe, Asia and America. PFAS measurements in sediment were <LOQ, with the exception of PFOS at Thabela Thabeng (2.36 ng/g dry weight (dw)). Average 11PFAS concentrations in biota increased along the gradient and ranged from <LOQ to 34.5 ng/g wet weight (ww) in invertebrates, <LOQ to 289 ng/g ww in liver and <LOQ to 34.0 ng/g ww in muscle tissue. Although PFOS concentrations were relatively high compared to literature, concentrations of other PFASs were rather low. A potential risk for humans through consumption of PFAS-contaminated fish was assessed. Tolerable daily intake values (grams of fish that can be eaten daily without risking health effects) were much lower than the average South African fish consumption per day, implying a potential risk for human health through consumption of PFAS contaminated fish
An assessment of applicability of existing approaches to predicting the bioaccumulation of conventional substances in nanomaterials
No full textThe experimental determination of bioaccumulation is challenging, and a number of approaches have been
developed for its prediction. It is important to assess the applicability of these predictive approaches to nanomaterials (NMs),
which have been shown to bioaccumulate. The octanol/water partition coefficient (KOW) may not be applicable to some NMs
that are not found in either the octanol or water phases but rather are found at the interface. Thus the KOW values obtained for
certain NMs are shown not to correlate well with the experimentally determined bioaccumulation. Implementation of
quantitative structure–activity relationships (QSARs) for NMs is also challenging because the bioaccumulation of NMs depends
on nano-specific properties such as shape, size, and surface area. Thus there is a need to develop new QSAR models based on
these new nanodescriptors; current efforts appear to focus on digital processing of NM images as well as the conversion of
surface chemistry parameters into adsorption indices. Water solubility can be used as a screening tool for the exclusion of NMs
with short half-lives. Adaptation of fugacity/aquivalence models, which include physicochemical properties, may give some
insights into the bioaccumulation potential of NMs, especially with the addition of a biota component. The use of kinetic
models, including physiologically based pharmacokinetic models, appears to be the most suitable approach for predicting
bioaccumulation of NMs. Furthermore, because bioaccumulation ofNMsdepends on a number of biotic and abiotic factors, it is
important to take these factors into account when one is modeling bioaccumulation and interpreting bioaccumulation result
Perfluorinated compounds in the aquatic food chains of two subtropical estuaries
No full textPer- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment and remain in largely unknown concentrations and with unknown effects on the African continent. Here we aimed to assess the presence of 15 PFASs in different compartments of the aMatikulu and uMvoti estuaries and to examine potential risks for human health through the consumption of contaminated fish. This is the first known study to assess PFASs in South African estuaries. Thirteen out of the fifteen PFASs were detected in water, sediment and biota samples from both estuaries, with perfluorooctanoic acid (PFOA), detected in every sample. PFOA concentrations from uMvoti water samples were the highest recorded to date in South African waters. PFOA was found in high concentrations in all water samples with an average range between 171 and 258 ng/L in the aMatikulu and 711–788 ng/L in the uMvoti. Perfluorooctane sulfonate (PFOS) concentrations in fish tissue samples were significantly higher than other PFASs. PFOS concentrations in all fish species caught in the aMatikulu ranged between 0.09 and 2.25 ng/g wet weight (ww) in muscle tissue and 1.5–12.08 ng/g ww in liver tissue, while PFOA concentrations ranged between 0.08 and 0.67 ng/g ww in muscle tissue and 0.54–1.48 ng/g ww in liver tissue. Concentrations of PFASs were only measured in Oreochromis mossambicus from the uMvoti and contained PFOS concentrations ranging from 0.18 to 0.97 ng/g ww in muscle tissue and 7.29–27.96 ng/g ww in liver tissue. PFOA concentrations ranged between 0.12 and 0.58 ng/g ww in muscle tissue and 0.17–1.01 ng/g ww in liver tissue. PFAS concentrations in all fish sampled were below the calculated Minimum Risk Levels (MRLs) for safe human consumptio
Influence of mining pollution on metal bioaccumulation and biomarker responses in cave dwelling fish, Clarias gariepinus
No full textCave ecosystems remain largely unstudied and risk being severely degraded as a result of anthropogenic activities. The Wonderfontein Cave, situated in the extensive gold mining region of the Witwatersrand Basin, is one such system that hosts a population of Clarias gariepinus, which is exposed to the influx of polluted mine water from the Wonderfontein Spruit River. The aim of this study was to investigate the bioaccumulation of metals, as well as relevant biomarkers, in C. gariepinus specimens sampled from the Wonderfontein Cave during high (April 2013) and low (September 2013) flow surveys. Results were also compared to a surface population associated with the Wonderfontein Spruit River. There were temporal differences in metal bioaccumulation patterns and this was attributed to the lack of dilution during the low flow period. Metals associated with acid mine drainage, i.e. Co, Mn and Zn were significantly higher in the Wonderfontein Cave population and were reflected in an increase in oxidative stress biomarkers (catalase, protein carbonyls and superoxide dismutase) and the induction of metallothionein, a biomarker of metal exposure. The surface population was exposed to metals associated with geological weathering processes, i.e. Fe and A
Comparative aquatic toxicity of gold nanoparticles and ionic gold using a species sensitivity distribution approach
No full textGold nanoparticles (nAu) are used in drug delivery systems allowing for targeted cellular distribution. The effects of increased use and release of nanoparticles into the environment are not well known. A species sensitivity distribution (SSD) allows for the ecotoxicological hazard assessment of a chemical based on single species toxicity tests. Aquatic toxicity needs to be related to particle characterization in order to understand the effects. The behaviour of nAu in the medium changed as the concentration increased. The toxic potential of ionic gold and nAu was expressed as a hazardous concentration where 5% of species will be harmed (HC5). The HC5 for nAu was much higher (42.78 mg/L) compared to the ionic gold (2.44 mg/L). The differences between the hazard potentials of nAu and ionic gold were attributed to the nAu not releasing any Au ions into solution during the exposures and following an aggregation theory response. Exposures to ionic gold on the other hand followed a clear dose dependent response based on the concentration of the ionic metal. Although SSDs present an indication of the relative hazard potential of nanoparticles, the true worth can only be achieved once other nanoparticle characteristics and their behavior in the environment are also considere
Response of zooplankton communities to altered water quality and seasonal flow changes in selected river dominated estuaries in KwaZulu-Natal, South Africa
No full textGlobally, estuaries are among the most productive ecosystems with many threatened by anthropogenic activities. Zooplankton is a bioindicator of ecosystem integrity. The spatial and temporal composition of zooplankton communities were quantified and compared within and between three estuaries (uMvoti, Thukela and aMatikulu/Nyoni estuaries) with different levels of human pressure in KwaZulu-Natal, South Africa. Additional effects of some physico-chemical variables and seasonal flow patterns to zooplankton community structuring were analyzed. The aMatikulu/Nyoni Estuary was selected as a reference site due to its good ecological state. Sampling dates represented high flow (March and April) and low flow (August and September) from 2014 to 2016. Following aMatikulu/Nyoni, highest abundance was recorded in Thukela and then uMvoti Estuary with copepod Pseudodiaptomus hessei and Acartia natalensis dominating the three estuaries. Highest abundance was recorded during low flow in the uMvoti and Thukela estuaries. Redundancy analysis revealed higher salinity and oxygen as environmental determinants of zooplankton community structure in the aMatikulu/Nyoni while turbidity and pH were the determinants of zooplankton community structures in uMvoti and Thukela estuaries. Elevated concentrations of DIN in the Thukela Estuary during high flow identifies the Thukela River as an important source of nitrogen to this estuary. Our findings suggest that these estuaries be managed to ensure sufficient freshwater supply which controls primary production. Although the three estuaries were from the same biogeographical region with a similar river dominated function, high variability in their zooplankton communities could be explained by differing water quality due to differing human pressure in their catchment
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