Paul J. Oberholster

The effects of engineered nanoparticles on survival, reproduction, and behaviour of freshwater snail, Physa acuta (Draparnaud, 1805)

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.

An overview of cyanobacterial bloom occurrences and research in Africa over the last decade

Cyanobacterial blooms are a current cause for concern globally, with vital water sources experiencing frequent and increasingly toxic blooms in the past decade. These increases are resultant of both anthropogenic and natural factors, with climate change being the central concern. Of the more affected parts of the world, Africa has been considered particularly vulnerable due to its historical predisposition and lag in social economic development. This review collectively assesses the available information on cyanobacterial blooms in Africa as well as any visible trends associated with reported occurrences over the last decade. Of the 54 countries in Africa, only 21 have notable research information in the area of cyanobacterial blooms within the last decade, although there is substantial reason to attribute these blooms as some of the major water quality threats in Africa collectively. The collected information suggests that civil wars, disease outbreaks and inadequate infrastructure are at the core of Africas delayed advancement. This is even more so in the area of cyanobacteria related research, with 11 out of 21 countries having recorded toxicity and physicochemical parameters related to cyanobacterial blooms. Compared to the rest of the continent, peripheral countries are at the forefront of research related to cyanobacteria, with countries such as Angola having sufficient rainfall, but poor water quality with limited information on bloom occurrences. An assessment of the reported blooms found nitrogen concentrations to be higher in the water column of more toxic blooms, validating recent global studies and indicating that phosphorous is not the only factor to be monitored in bloom mitigation. Blooms occurred at low TN: TP ratios and at temperatures above 12°C. Nitrogen was linked to toxicity and temperature also had a positive effect on bloom occurrence and toxicity. Microcystis was the most ubiquitous of the cyanobacterial strains reported in Africa and the one most frequently toxic. Cylindrospermopsis was reported more in the dry, north and western parts of the continent countries as opposed to the rest of the continent, whilst Anabaena was more frequent on the south eastern regions. In light of the entire continent, the inadequacy in reported blooms and advances in this area of research require critical intervention and action.

Applying genotoxicology tools to identify environmental stressors in support of river management

Although bioassay approaches are useful for identifying chemicals of potential concern, they provide little understanding of the mechanisms of chemical toxicity. Without this understanding, it is difficult to address some of the key challenges that currently face aquatic ecotoxicology. To overcome this, the toxicity potential of the water samples was assessed and surviving organisms (Physa acuta) were used for protein activity measurements and gene expression profiling by making use of complementary DNA amplified fragment length polymorphism (cDNA-AFLP) analysis. From the data it was evident that the impacts of specific pollutants (e.g. sewage) on organisms at the cellular level could be identified, and that the expressed stressor genes can be used as bioindicators/markers/genetic signatures or fingerprints during identification of point source pollution. From an ecosystem management point of view these insights could assist with the forecasting and reduction of environmental risks on catchment level by implementing suitable management interventions.

River catchment responses to anthropogenic acidification in relationship with sewage effluent: An ecotoxicology screening application

Rising environmental pressures on water resources and resource quality associated with urbanisation, industrialisation, mining and agriculture are a global concern. In the current study the upper Olifants River catchment as case study was used, to show that acid mine drainage (AMD) and acid precipitation were the two most important drivers of possible acidification during a four-year study period. Over the study period 59% of the precipitation sampled was classified as acidic with a pH value below 5.6. Traces of acidification in the river system using aquatic organisms at different trophic levels were only evident in areas of AMD point sources. Data gathered from the ecotoxicology screening tools, revealed that discharge of untreated and partially treated domestic sewage from municipal sewage treatment works and informal housing partially mitigate any traces of acidification by AMD and acid precipitation in the main stem of the upper Olifants River. The outcome of the study using phytoplankton and macroinvertebrates as indicator organisms revealed that the high loads of sewage effluent might have played a major role in the neutralization of acidic surface water conditions caused by AMD and acid precipitation. Although previous multi-stage and microcosm studies confirmed the decrease in acidity and metals concentrations by municipal wastewater, the current study is the first to provide supportive evidence of this co-attenuation on catchment scale. These findings are important for integrated water resource management on catchment level, especially in river systems with a complex mixture of pollutants.

Eco-epidemiological and pathological features of wildlife mortality events related to cyanobacterial biointoxication in the Kruger National Park, South Africa

Over the past decade, several clustered, multispecies, wildlife mortality events occurred in the vicinity of two man-made earthen dams in the southern and south central regions of the Kruger National Park, South Africa. On field investigation, heavy cyanobacterial blooms were visible in these impoundments and analysis of water samples showed the dominance of Microcystis spp. (probably Microcystis aeruginosa). Macroscopic lesions seen at necropsy and histopathological lesions were compatible with a diagnosis of cyanobacterial intoxication. Laboratory toxicity tests and assays also confirmed the presence of significant levels of microcystins in water from the two dams. These outbreaks occurred during the dry autumn and early winter seasons when water levels in these dams were dropping, and a common feature was that all the affected dams were supporting a large number of hippopotamuses (Hippopotamus amphibius). It is hypothesised that hippopotamus’ urine and faeces, together with agitation of the sediments, significantly contributed to internal loading of phosphates and nitrogen – leading to eutrophication of the water in these impoundments and subsequent cyanobacterial blooms. A major cause for concern was that a number of white rhinoceros (Ceratotherium simum) were amongst the victims of these bio-intoxication events. This publication discusses the eco-epidemiology and pathology of these clustered mortalities, as well as the management options considered and eventually used to address the problem.

Linking hydro‐morphology with invertebrate ecology in diverse morphological units of a large river‐floodplain system

Fil: Blettler, Martin Cesar Maria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto Nacional de Limnologia. Universidad Nacional del Litoral. Instituto Nacional de Limnologia; Argentina

A Watershed Approach in Identifying Key Abiotic Ecosystem Drivers in Support of River Management: a Unique Case Study

Since the industrial revolution, the impact of effluents produced by human activities on ecosystems has been a major international environmental concern. This study was aimed at observing the changes in water and sediment qualities at a watershed level of two different river systems facing the same land use practices, but impacted to different degrees. Samples were collected at strategically selected sites within the mainstream of both rivers, the major tributaries draining into them, as well as a major impoundment in each system. A distinct difference between the two different rivers was observed. It was established that certain variables, for example pH, contributed to the differential water and sediment quality signatures in the upper Olifants and Mokolo rivers, having important considerations for the future management of both river ecosystems. Other abiotic factors, such as alkalinity and sulphate levels, were also found to be important. The tributaries were found to play an important role in the purification and/or pollution of the mainstream rivers. On the other hand, the present impoundments in the Mokolo River were observed to affect the water and sediment qualities downstream. Overall, through the use of comparative models, it was observed that the upper Olifants River was in a different state than the Mokolo River and the information from this study may aid in the future management of the Mokolo River to prevent a shift to an undesirable state.

Thyroid function of steatitis-affected Mozambique tilapia Oreochromis mossambicus from a sub-tropical African reservoir

Thyroid function and nutritional indicators were measured in obese, steatitis-affected Mozambique tilapia Oreochromis mossambicus from Loskop Reservoir (LR), South Africa. Plasma thyroid hormones (especially T3) and thyroid follicle histomorphology revealed high levels of activity in every aspect of the thyroid cascade measured in fish from LR compared to a reference population of steatitis-free fish. Concurrent measurements of nutritional state including plasma lipids, liver lipid content and hepatocyte size showed that fish from LR had significant energy stores indicative of abundant nutritional intake. There were distinct sex and seasonal differences, with the highest plasma lipids and T3 levels observed in steatitis-affected females during spring and summer. Positive correlations were observed between plasma lipids (especially cholesterol) and T3 concentrations in fish from both populations, indicating a link between lipid metabolism and thyroid function. There was no direct evidence of thyroid disruption, but this cannot be ruled out until further research determines the factors that underlie the homeostatic shift leading to elevated plasma and liver lipids and T3 levels in steatitis-affected tilapia.