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ABSTRACT: Studies were conducted to determine the effects of a panel of seven nanomaterials (NMs), namely: α-alumina, γ-alumina, precipitated silica; silica fume, calcined silica fume, colloidal antimony pentoxide (Sb(2)O(5)), and superfine amorphous ferric oxide (Fe(2)O(3)), on sediment dwelling invertebrates Chironomus tentans under controlled laboratory conditions. Percentage survival, enzyme activities, growth development, and DNA fragmentation parameters were studied as acute, biochemical, and physiological toxicities of NMs, respectively. Quantitation of catalase and peroxidase enzyme activity demonstrated that toxicant stress of the NMs increased enzyme activity in a concentration dependent fashion across all treatments. The percentage growth length of the test specimens exposed to different NMs was significantly reduced compared to the negative control while only five concentrations were not in the toxic range, namely; Fe(2)O(3) (5 μg/kg); silica fume (5 μg/kg, 50 μg/kg); Sb(2)O(5) (5 μg/kg) and calcined silica fume (5 μg/kg). Genotoxic stress assessed by use of DNA laddering showed complementary findings to the other ecotoxicological endpoints tested in this study--the percentage survival and growth length inhibition.
Ecotoxicology and Environmental Safety 01/2011; 74(3):416-23. · 2.29 Impact Factor
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ABSTRACT: Increasing uses of engineered nanoparticles (ENPs) in commercial products and industrial applications has eventually resulted to their releases into atmospheric, terrestrial, and aquatic environments. However, knowledge gaps in ENPs toxicity, fate, and behaviour currently limit our ability to quantify risk assessment of materials with nanoscale dimensions, and therefore, the extent of the resultant environmental impacts remains unknown. In the present study, we evaluated the effects of γ-alumina, α-alumina, modified TiO(2) (M-TiO(2)), and commercial TiO(2) (C-TiO(2)) ENPs on the survival, behaviour, and early life stages of the freshwater snail Physa acuta (Draparnaud). The toxicity evaluation was carried out after spiking commercial sand with ENPs concentrations of 0.005, 0.05, or 0.5 gk g(-1). Our findings suggest that increases of γ-alumina and α-alumina concentrations at sub-lethal level concentrations caused significant reduction in the embryo growth rate and embryo hatchability. In addition, these ENPs induced observable developmental deformities of the embryos. In addition, toxicity evaluations using acute 96-h and chronic 28-d tests showed exposure duration may be a significant factor in ENPs-induced toxicity. Therefore, long-term exposure of aquatic organisms to ENPs - potentially can alter certain ecological populations at different trophic levels - and may compromise the entire aquatic ecological functionality. The percentage hatchlings in test chambers containing 0.5 gk g(-1) γ-alumina and α-alumina concentration was 50% less to those observed in the controls. Our results suggest the embryonic growth and hatchability tests are useful endpoints in chronic sediment toxicity tests for determining the toxic thresholds of ENPs in sediment environment. Although no snail mortalities were observed during the static 96-h test containing sediment spiked with different concentrations of M-TiO(2), C-TiO(2), γ-alumina and α-alumina - the antioxidant enzymatic assay results indicated a significant change in antioxidant levels which altered peroxidation at 0.05 or 0.5 gk g(-1)concentrations for both γ-alumina and α-alumina.
Chemosphere 10/2010; 81(10):1196-203. · 3.21 Impact Factor
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ABSTRACT: The relationships between water quality and the phytoplankton community within Lake Loskop were studied during the late summer and autumn of 2008 to evaluate the impacts of acid mine drainage and high nutrient concentrations. The higher concentrations of metal ions and sulphate had adverse effects on certain phytoplankton species in the inflowing riverine zone of Lake Loskop, in comparison to the reference site in the lacustrine zone of the lake, which was dominated by the larger and slower growing late summer species of Coelastrum reticulum Nägeli, Straurastrum anatinum Meyen ex Ralfs and Ceratium hirundinella Müller. The high nutrient concentrations (nitrogen: 17 mg l(-1) and orthophosphate: 0.7 mg l(-1)) during the mid-summer peak of the rainy season were associated with the development of a bloom of the cyanobacterium Microcystis. Water quality data associated with the development of the Microcystis bloom suggest that the aquatic system of Lake Loskop has now entered an alternate, hypertrophic regime. This change overshadowed the adverse effects of high concentrations of heavy metal ions and low pH. Throughout this study, the reference site in the lacustrine zone of Lake Loskop had lower concentrations of metal ions and sulphate, and higher pH values. The response of phytoplankton bioassays on integrated water samples from the different sampling sites did provide potential answers to the reasons for the absence of the algal group Chlorophyceae in the phytoplankton community structure in the riverine zone of the lake.
Ecotoxicology and Environmental Safety 11/2009; 73(3):326-35. · 2.29 Impact Factor
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ABSTRACT: Macroinvertebrate communities in Rietvlei nature reserve wetland area and their relationship with water quality were studied with the aim to evaluate their use as potential indicators of pollution. Sampling locations were selected to include outlets from sewage effluent, agricultural and informal residential runoff. A large increase in nutrient concentrations was observed downstream from discharged treated sewage with an associated decrease in species richness. Bioassays performed included: Daphnia magna, Hydra attenuate, Lactuca sativa, Allium cepa and Pyxicephalus adspersus. The highest percentage of lethality response to a screen (100% concentration) of sampled wetland water by test specimens were observed at the point source input of the Hartbeespoort treated sewage plant. Data generated from the AUSRIVAS method and multitrophic level bioassays revealed the deterioration of the wetland possibly due to factors such as increasing urbanization, industrialization, agriculture runoff and rapid human settlement in the Hennops River catchment area and its principal tributaries.
Environmental pollution (Barking, Essex: 1987) 03/2008; 156(1):184-92. · 3.43 Impact Factor
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ABSTRACT: This paper describes the results of the investigation of a shallow urban lake before, and a second year after, restoration to determine the effects of aeration and bottom-sediment removal on the trophic state and environmental variables controlling the lake's phytoplankton, macrovertebrates and zooplankton compositions. The anthropogenic eutrophic process of the lake is characterized by increased nutrient concentrations from urban run-off inputs. This addition triggers a chain of events that start with a massive increase in the growth of primary producers, as these are generally growth-limited by nutrients in freshwater ecosystems. Although the lake was artificially mixed, nuisance cyanobacteria were dominant as primary producers the second year after restoration, during the summers of 2004 and 2005, until this population collapsed and were replaced by diatoms after periods of high winds, rainfall and a decreased temperature. The absence of macrophytes in the main basin because of the removal of bottom sediment had a major effect on macroinvertebrates and zooplankton. Daphnia sp. was the dominant zooplankton species before restoration, being replaced by Bosmina sp., possibly because of the lack of refuge by macrophytes. As an alternative, Bosmina sp. used the surface blooms of cyanobacteria in summer as refuge from grazing by planktivorous fish. The greatest disturbance on the macroinvertebrate community richness and evenness was the decline of scrapers and shredders, because of the lack of macrophytes after removal of the lake bottom sediment.
Lakes & Reservoirs Research & Management 07/2007; 12(2):73 - 86.
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ABSTRACT: One of the most severe problems associated with eutrophication of urban freshwater ecosystems is the occurrence of increasingly frequent blooms of toxic cyanobacteria. Cyanotoxins might accumulate in the trophic web, producing diverse intoxication symptoms and chronic effects that are difficult to diagnose and prevent. High mortality of domestic animals and fish has been reported previously under these prevailing conditions. This study investigates the taxonomic composition of phytoplankton assemblages in Sheldon Lake during the summer of 2004, a year after the completion of a restoration project on the lake. The study analysed the physical and chemical changes caused by urban run-off and artificial mixing, as well as the usefulness of microcystin molecular markers derived from the mcy gene cluster for the detection of toxic cyanobacterial strains in environmental samples from Sheldon Lake. This study clearly demonstrates that the artificial mixing rate alone was insufficient to cause a transition to a well-mixed aquatic system, and that cyanobacteria remained dominant throughout the summer months. The presence of toxic cyanobacterial strains was confirmed with the use of molecular markers that detected the presence of the mcy gene cluster responsible for the production of toxin by Microcystis spp. This approach might have a great potential use in the routine analyses of urban aquatic ecosystems. It also might make toxicity monitoring more feasible, allowing for the early application of corrective actions, especially for cases such as Sheldon Lake, which is a public recreational focal point.
Lakes & Reservoirs Research & Management 05/2006; 11(2):111 - 123.
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ABSTRACT: This survey provides information on sediment toxicity and structural characteristics of the macroinvertebrates and benthic phytoplankton at 10 locations in the Cache la Poudre River after long-term exposure to coal tar residue. The application of the Australian river bioassessment system (AUSRIVAS) as well as a biotest battery was used to evaluate the river 'health' condition. Coal tar is a dense nonaqueous-phase liquid of significant environmental concern due to its toxicity and persistence in the subsurface. Organisms like Selenastrum capricornutum, Daphnia magna and Chironomus tentans, representing different complexities in the biosphere, were selected as test systems for ecotoxicological studies. The results obtained in this study indicate that a biotest battery, macroinvertebrate and benthic phytoplankton communities are in principle suitable biological tools for evaluation of toxic oil and coal-derived substances in long-term contaminated river sediment.
Water Research 01/2006; 39(20):4913-24. · 4.86 Impact Factor
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ABSTRACT: The relationships between water quality and the phytoplankton community within Lake Loskop were studied during the late summer and autumn of 2008 to evaluate the impacts of acid mine drainage and high nutrient concentrations. The higher concentrations of metal ions and sulphate had adverse effects on certain phytoplankton species in the inflowing riverine zone of Lake Loskop, in comparison to the reference site in the lacustrine zone of the lake, which was dominated by the larger and slower growing late summer species of Coelastrum reticulum Nägeli, Straurastrum anatinum Meyen ex Ralfs and Ceratium hirundinella Müller. The high nutrient concentrations (nitrogen: 17 mg l−1 and orthophosphate: 0.7 mg l−1) during the mid-summer peak of the rainy season were associated with the development of a bloom of the cyanobacterium Microcystis. Water quality data associated with the development of the Microcystis bloom suggest that the aquatic system of Lake Loskop has now entered an alternate, hypertrophic regime. This change overshadowed the adverse effects of high concentrations of heavy metal ions and low pH. Throughout this study, the reference site in the lacustrine zone of Lake Loskop had lower concentrations of metal ions and sulphate, and higher pH values. The response of phytoplankton bioassays on integrated water samples from the different sampling sites did provide potential answers to the reasons for the absence of the algal group Chlorophyceae in the phytoplankton community structure in the riverine zone of the lake.
Ecotoxicology and Environmental Safety.
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ABSTRACT: Macroinvertebrate communities in Rietvlei nature reserve wetland area and their relationship with water quality were studied with the aim to evaluate their use as potential indicators of pollution. Sampling locations were selected to include outlets from swage effluent, agricultural and informal residential runoff. A large increase in nutrient concentrations was observed downstream from discharged treated sewage with an associated decrease in species richness. Bioassays performed included: Daphnia magna, Hydra attenuate, Lactuca sativa, Allium cepa and Pyxicephalus adspersus. The highest percentage of lethality response to a screen (100% concentration) of sampled wetland water by test specimens were observed at the point source input of the Hartbeespoort treated sewage plant. Data generated from the AUSRIVAS method and multitrophic level bioassays revealed the deterioration of the wetland possibly due to factors such as increasing urbanization, industrialization, agriculture runoff and rapid human settlement in the Hennops River catchment area and its principal tributaries.
Environmental Pollution.
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ABSTRACT: Studies were conducted to determine the effects of a panel of seven nanomaterials (NMs), namely: α-alumina, γ-alumina, precipitated silica; silica fume, calcined silica fume, colloidal antimony pentoxide (Sb2O5), and superfine amorphous ferric oxide (Fe2O3), on sediment dwelling invertebrates Chironomus tentans under controlled laboratory conditions. Percentage survival, enzyme activities, growth development, and DNA fragmentation parameters were studied as acute, biochemical, and physiological toxicities of NMs, respectively. Quantitation of catalase and peroxidase enzyme activity demonstrated that toxicant stress of the NMs increased enzyme activity in a concentration dependent fashion across all treatments. The percentage growth length of the test specimens exposed to different NMs was significantly reduced compared to the negative control while only five concentrations were not in the toxic range, namely; Fe2O3 (5 μg/kg); silica fume (5 μg/kg, 50 μg/kg); Sb2O5 (5 μg/kg) and calcined silica fume (5 μg/kg). Genotoxic stress assessed by use of DNA laddering showed complementary findings to the other ecotoxicological endpoints tested in this study—the percentage survival and growth length inhibition.
Ecotoxicology and Environmental Safety.
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ABSTRACT: Data generated during 12 fi eld trips in 2006 were used to investigate possible changes in the biota com-munities of Lake Tswaing after a borehole was sunk in 1988/89 near the centre of the crater lake. The Tswaing meteorite crater lake is a small (0.07 km 2), shallow (maximum depth 2.1 m), alkaline (surface water pH varied from 9.6 to 10.3), meromictic lake with a Secchi disk transparency of between 6 and 12 cm. The lake had a distinct surface layer of cyanobacteria (Arthrospira fusiformis), located above a layer of purple sulphur bacteria, that was located, in turn, above a layer of green sulphur bacteria. This is the fi rst report on the presence of sulphur bacteria in the lake. The absence of submerged and emergent aquatic macrophytes in the lake limits habitat diversity for attached diatoms in the littoral regions. Both the numbers of families and the density of the benthic invertebrates were very low. The dominant invertebrate groups present were Nematodes, Muscidae and Hydrophilidae. Seven macroinvertebrate families were recorded, fi ve of which are new to Lake Tswaing. In addition, the periphytic ciliate Blepharisma sp. was also observed for the fi rst time within the land/water contact zone of Lake Tswaing. Benthic diatoms were scarce and the dominant species present was Gyrosigma rautenbachiae, while Nitzschia quadrangula was the dominant planktonic diatom, previously not recorded in the main basin of the lake. The diatom species Nitzschia communis, although in low numbers, was also not reported in previous studies of Lake Tswaing.
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ABSTRACT: Toxic freshwater cyanobacterial blooms are potential health hazards in water supply reservoirs and therefore predicting bloom events is an important goal of monitoring fresh water programmes. The recent identification of the mcygenes in the production of microcystin synthetase for the first time provides an avenue to study microcystin production at a genetic level. This paper reports analysis of a winter cyanobacterial bloom by use of quantitative real-time PCR, ELISA and PP2A methods for detection of strains present and determination of their toxigenicity in Lake Midmar South Africa. We further investigated the taxonomic composition of phytoplankton at different sampling sites and the physical and chemical changes caused in the surface water of Lake Midmar by waterfowl. Our study clearly demonstrates that the interaction between low surface water temperatures and productivity was overshadowed by the response to nutrients and nutrient availability. We also confirmed the presence of the toxic cyanobacterial strains through the use of molecular markers that detect the presence of some of the mcygenes in the mcygene cluster that is able to synthesize microcystin toxins in Microcystis spp.
African Journal of Biotechnology (ISSN: 1684-5315) Vol 6 Num 15.
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ABSTRACT: This survey provides information on sediment toxicity and structural characteristics of the macroinvertebrates and benthic phytoplankton at 10 locations in the Cache la Poudre River after long-term exposure to coal tar residue. The application of the Australian river bioassessment system (AUSRIVAS) as well as a biotest battery was used to evaluate the river ‘health’ condition. Coal tar is a dense nonaqueous-phase liquid of significant environmental concern due to its toxicity and persistence in the subsurface. Organisms like Selenastrum capricornutum, Daphnia magna and Chironomus tentans, representing different complexities in the biosphere, were selected as test systems for ecotoxicological studies. The results obtained in this study indicate that a biotest battery, macroinvertebrate and benthic phytoplankton communities are in principle suitable biological tools for evaluation of toxic oil and coal-derived substances in long-term contaminated river sediment.
Water Research.
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ABSTRACT: Laboratory experiments provide no general answer to the question of whether zooplankton affects cyanobacteria or are affected by prokaryotes. A cyanobacterium may be grazed upon as small colonies, and the same species, as larger colonies, may inhibit zooplankton feeding. Within zooplankton, different species or groups may be affected differently. With this background we set out to detect winter zooplankton grazing and toxicity of overwintering populations of Microcystis aeruginosa. A polymerase chain reaction (PCR) method with oligonucleotide primers for the mcy gene cluster that encodes microcystin synthetase was employed for detection of M. aeruginosa reminiscent products in grazing cladocera. In our field studies, we detected the mcy gene cluster in strains of overwintering colonies of benthic Microcystis and also confirmed the expression of toxicity by quantitative PCR, phosphatase inhibition and enzyme-linked immunosorbent assays (ELISA). We further confirmed the presence of the mcy gene cluster in DNA and RNA isolated from sampled Daphnia magna specimens, indicating that zooplankton in the natural environment may ingest toxic Microcystis cells as part of their diet during winter months.
Harmful Algae.
