Using pollution indices to develop a risk classification tool for gold mining contaminated soils.

The presence of potentially toxic elements (PTEs) in soil and plants is a risk factor to human well-being and the environment. Soil and leaves from a traditional medicinal plant, Vachellia karroo, known as the sweet thorn plant, were assessed to determine the extent of pollution by PTEs from gold mine tailings in a case study area of Matjhabeng Local Municipality, South Africa. A risk classification tool was developed using the different indicators of pollution quantified to describe the pollution risk at each sampling site. High concentrations of copper, cadmium, lead, nickel, and zinc were measured in the soil, which exceeded the maximum permissible soil quality limits. The enrichment factor and geoaccumulation index results also confirmed heavy soil pollution by copper, nickel, and zinc, with exceptionally heavy pollution by cadmium and selenium. The PTEs in the soil were in an exchangeable form, with the sweet thorn plant accumulating lead and selenium at toxic levels, which poses a risk to the health of the local people as the plant is used for medicinal purposes. The overall pollution risk classification tool of the sampling sites showed that 17% were high-risk areas, 53% were moderate-risk areas, and 20% of the sites were low-risk areas.

Assessment of water, sanitation, and hygiene target and theoretical modeling to determine sanitation success in sub-Saharan Africa.

Accessing the status of clean drinking water, sanitation, and hygiene remains a challenge in sub-Saharan Africa (SSA). The current article contributes to the progress made by the WASH initiatives in ten SSA countries in eliminating open defecation by 2030, using theoretical data from 2017 to 2019. The authors used regression trend estimation to observe that rural and urban population growth had a statistically significant detrimental influence on the elimination of open defecation by 2030. According to the predicted data model, by 2030-2035, the urban population of SSA would be 65, 25, and 10 million in all the three categories of income groups. An increase in the number of modern pit users (C1) shows no improvement at the annual rate of change. The unimproved toilets and open-pit latrines (C2 and C3) show a linear growth rate, which expanded over time. Population growth, higher unemployment, and teen pregnancies contribute to this increase. Under current conditions, the curve of modern pit latrine users will increase linearly. Nigeria has the most significant number of spread pit latrine users, which has decreased linearly from 25 to 20% since 2017. It was evident that the power-law trend in Nigeria would increase the usage of unimproved pit latrines and open-pit latrines. Ghana had the highest rate (50%) of open-pit latrine users, while the data show that this situation remained stable (2001-2017). In the Democratic Rep. Congo, annual rates increased linearly from 25 to 33% (2000-2017), while Burundi was one of the countries in the region with the lowest number of open-pit latrine users, although the annual rate has increased from 6.13 to 11.75% since 2017 to 2019. Supplementary Information: The online version contains supplementary material available at 10.1007/s10668-022-02620-z.

Aquatic Environment Exposure and Toxicity of Engineered Nanomaterials Released from Nano-Enabled Products: Current Status and Data Needs.

Rapid commercialisation of nano-enabled products (NEPs) elevates the potential environmental release of engineered nanomaterials (ENMs) along the product life cycle. The current review examined the state of the art literature on aquatic environment exposure and ecotoxicity of product released (PR) engineered nanomaterials (PR-ENMs). Additionally, the data obtained were applied to estimate the risk posed by PR-ENMs to various trophic levels of aquatic biota as a means of identifying priority NEPs cases that may require attention with regards to examining environmental implications. Overall, the PR-ENMs are predominantly associated with the matrix of the respective NEPs, a factor that often hinders proper isolation of nano-driven toxicity effects. Nevertheless, some studies have attributed the toxicity basis of observed adverse effects to a combination of the released ions, ENMs and other components of NEPs. Notwithstanding the limitation of current ecotoxicology data limitations, the risk estimated herein points to an elevated risk towards fish arising from fabrics' PR-nAg, and the considerable potential effects from sunscreens' PR-nZnO and PR-nTiO2 to algae, echinoderms, and crustaceans (PR-nZnO), whereas PR-nTiO2 poses no significant risk to echinoderms. Considering that the current data limitations will not be overcome immediately, we recommend the careful application of similar risk estimation to isolate/prioritise cases of NEPs for detailed characterisation of ENMs' release and effects in aquatic environments.

Comparison of phytoplankton control measures in reducing cyanobacteria assemblage of reservoirs found in the arid region of Southern Africa.

Ecological restorations of reservoirs are implemented worldwide; however, minimal successes are reported and understood for warmer African lakes like Swakoppoort Dam, Namibia. The objectives of the study were (a) to establish the effectiveness of the two control measures in reducing cyanobacteria growths in comparison with untreated control areas and (b) to compare the results generated before and after control measures with the reference Von Bach Dam. During Phoslock® treatment, the average cyanobacteria cells and total phosphate (TP) were 90,521 cells/ml and 0.3 mg/L in the treated area and 55,338 cells/ml and 0.1 mg/L in the control area. During Solar Powered Circulation (SPC) treatment, the average cyanobacteria cells were on average 906,420 cells/ml in the treated areas and 121,891 cells/ml in the control area. The TP on average was 0.3 mg/L during SPC treatment, while during the combined treatment, the average cyanobacteria cells, TP, and total nitrogen (TN) were 18,387,226 cells/ml, 0.27 mg/L, and 2.41 mg/L before and 22,836,511 cells/ml, 0.42 mg/L, and 1.50 mg/L after treatment. This was higher compared to the reference site. PCA triplot indicates no grouping pattern, and the repeated-measures mixed model analyses indicate that treatment had no significant effect on cyanobacteria cells. It was evident that the two control measures were ineffective in reducing cyanobacterial cells. PRACTITIONER POINTS: Key findings of the article: Two phytoplankton control measures were found ineffective to reduce the cyanobacterial cell numbers. High cell numbers of cyanobacteria were recorded at the treatment areas compared to untreated control areas during both treatments. The combined effect of the two control measures was ineffective as more cyanobacterial cells were recorded during the treatment. During control measure treatment, the Swakoppoort Dam was hypertrophic, which could be due to a malfunctioned WWTP upstream. The inefficiency of the control measures could be due to small treatment area, higher nutrients, or treatment period. The implications of the results to water/wastewater practice: The selection of appropriate mitigation measures considering treatment area for dams with high nutrient situated in warmer arid environments. There is a need to understand the trophic relationships, climatic conditions, and the sources of the internal and external nutrients to manage water quality. Focus on point and non-point sources of nutrients as the root causes of the degradation of Swakoppoort Dam water.

Will the extraction of COVID-19 from wastewater help flatten the curve?

With the potentially fatal effect of COVID-19 and its devastating impact on economies worldwide, some environmental scientist has suggested the use of waste from household sewage to trace the movement of SARS-CoV-2, within a given country. However, this approach is not without challenges where developing countries lack proper and adequate hygiene and sanitation, resulting in widespread defecation. Limited scientific research has been done to determine how many times a recently infected person can defecate and the quantification of SARS-CoV-2 found in a single expel. On the other hand, there is no detailed research to specify where the heavy viral load of SARS-CoV-2 can be found in human excreta. In this paper, we present some obstacles that this approach could face in the absence of an intense lockdown in developing nations such as sub-Saharan countries. To achieve this, we identify some research needs that will strengthen our understanding of the transmission, occurrence, and persistence of SARS-CoV-2 in sewage and wastewater, including the life-span that depends on temperature. A methodology to follow in the process of identifying a hotspot on a small scale using some mathematical distributions, including the normal distribution, log-normal distribution, and the most complex one known as Blancmange function, was presented with some examples. Our investigation showed that this method might have some challenges, especially in developing countries (sub-Sahara countries) where open latrine usage is very high. Some recommendations we suggested to ensure the efficiency of such a method on a small scale. However, in general, it is essential to note the extraction/detection method will not help more than the testing method used all over the world to trace SARS-CoV-2 -19 in humans.

Dataset of metal(loid) concentrations recorded in the tissues of two fish species from Flag Boshielo Dam, South Africa.

Metal(loid) pollution in aquatic ecosystems has become a cause for concern, particularly in areas where communities depend on services from these systems for their livelihood. This dataset presents the metal(loi) concentrations recorded in the water column, bottom sediment, and tissues of Oreochromis mossambicus and Labeo rosae from Flag Boshielo Dam, an impoundment in one of the most polluted river systems in Southern Africa, the Olifants River. The concentrations of metal(loid)s were measured using inductively coupled plasma-optical emission spectrophotometry (ICP-OES; Perkin Elmer, Optima 2100DV). The data generated attest that in aquatic ecosystems, metal(loid)s do not remain in suspension in the water column, but sink down to the bottom sediment where they accumulate or get taken up by receptor organisms such as fish. It further confirm that there is a clear separation on the extent to which metal(loid)s are accumulating in different tissues and liver mostly accumulate higher concentration followed by gills and muscle, respectively. These data can be useful to guide future studies aiming to understand the dynamics, pathways and fate of metal(loid)s in relation to water, sediment and fish tissues. These data can also be used for decision making in relation to the establishment of freshwater fisheries in dams receiving metal(loid)s from different land use activities.

Factors facilitating sustainable scientific partnerships between developed and developing countries.

International scientific partnerships are key to the success of strategic investments in plant science research and the farm-level adoption of new varieties and technologies, as well as the coherence of agricultural policies across borders to address global challenges. Such partnerships result not only in a greater impact of published research enhancing the career development of early and later stage researchers, but they also ensure that advances in plant science and crop breeding technologies make a meaningful contribution to society by brokering acceptance of emerging solutions to the world problems. We discuss the evidence showing that despite a lack of funding, scientists in some African countries make a significant contribution to global science output. We consider the criteria for success in establishing long-term scientific partnerships between scientists in developing countries in Southern Africa ("the South") and developed countries such as the UK ("the North"). We provide our own personal perspectives on the key attributes that lead to successful institutional collaborations and the establishment of sustainable networks of successful "North-South" scientific partnerships. In addition, we highlight some of the stumbling blocks which tend to hinder the sustainability of long-term "North-South" scientific networks. We use this personal knowledge and experiences to provide guidelines on how to establish and maintain successful long-term "North-South" scientific partnerships.

Metal levels in two fish species from a waterbody impacted by metallurgic industries and acid mine drainage from coal mining in South Africa.

The Loskop Dam in South Africa is the most contaminated waterbody in the Olifants River which is a transboundary river that flows into Mozambique. The present study measured selected metal concentrations in the muscle of Labeo rosae and Oreochromis mossambicus from Loskop Dam, and assessed the human health risks associated with consumption of these fish species. Trace metals were below detection level in the surface water whereas bottom sediment exhibited relatively higher concentrations. A significant seasonal variations (p < 0.05) as well as inter-species difference (p < 0.05) of metal concentrations were observed in the fish muscle. Selenium concentration showed to have increase over the recent few years. Concentrations exceeding permissible level for human consumption was recorded for As, Se and Sb in both species. Other metals which THQ > 1 was Cr for L. rosae and Co for O. mossambicus. The current study shows that there could be some serious health and environmental implications for rural communities making use of Loskop Dam fish as food source. These findings add to knowledge in Africa, particularly South Africa, where other fish species have been identified as being potentially dangerous for human consumption in terms of Se, Sb, As, Co and Cr levels.

The Presence of Toxic and Non-Toxic Cyanobacteria in the Sediments of the Limpopo River Basin: Implications for Human Health.

The presence of harmful algal blooms (HABs) and cyanotoxins in drinking water sources poses a great threat to human health. The current study employed molecular techniques to determine the occurrence of non-toxic and toxic cyanobacteria species in the Limpopo River basin based on the phylogenetic analysis of the 16S rRNA gene. Bottom sediment samples were collected from selected rivers: Limpopo, Crocodile, Mokolo, Mogalakwena, Nzhelele, Lephalale, Sand Rivers (South Africa); Notwane (Botswana); and Shashe River and Mzingwane River (Zimbabwe). A physical-chemical analysis of the bottom sediments showed the availability of nutrients, nitrates and phosphates, in excess of 0.5 mg/L, in most of the river sediments, while alkalinity, pH and salinity were in excess of 500 mg/L. The FlowCam showed the dominant cyanobacteria species that were identified from the sediment samples, and these were the Microcystis species, followed by Raphidiopsis raciborskii, Phormidium and Planktothrix species. The latter species were also confirmed by molecular techniques. Nevertheless, two samples showed an amplification of the cylindrospermopsin polyketide synthetase gene (S3 and S9), while the other two samples showed an amplification for the microcystin/nodularin synthetase genes (S8 and S13). Thus, these findings may imply the presence of toxic cyanobacteria species in the studied river sediments. The presence of cyanobacteria may be hazardous to humans because rural communities and farmers abstract water from the Limpopo river catchment for human consumption, livestock and wildlife watering and irrigation.

Development of a diatom-based multimetric index for acid mine drainage impacted depressional wetlands.

Acid mine drainage (AMD) from coal mining in the Mpumalanga Highveld region of South Africa has caused severe chemical and biological degradation of aquatic habitats, specifically depressional wetlands, as mines use these wetlands for storage of AMD. Diatom-based multimetric indices (MMIs) to assess wetland condition have mostly been developed to assess agricultural and urban land use impacts. No diatom MMI of wetland condition has been developed to assess AMD impacts related to mining activities. Previous approaches to diatom-based MMI development in wetlands have not accounted for natural variability. Natural variability among depressional wetlands may influence the accuracy of MMIs. Epiphytic diatom MMIs sensitive to AMD were developed for a range of depressional wetland types to account for natural variation in biological metrics. For this, we classified wetland types based on diatom typologies. A range of 4-15 final metrics were selected from a pool of ~140 candidate metrics to develop the MMIs based on their: (1) broad range, (2) high separation power and (3) low correlation among metrics. Final metrics were selected from three categories: similarity to reference sites, functional groups, and taxonomic composition, which represent different aspects of diatom assemblage structure and function. MMI performances were evaluated according to their precision in distinguishing reference sites, responsiveness to discriminate reference and disturbed sites, sensitivity to human disturbances and relevancy to AMD-related stressors. Each MMI showed excellent discriminatory power, whether or not it accounted for natural variation. However, accounting for variation by grouping sites based on diatom typologies improved overall performance of MMIs. Our study highlights the usefulness of diatom-based metrics and provides a model for the biological assessment of depressional wetland condition in South Africa and elsewhere.

An evaluation of the endocrine disruptive potential of crude oil water accommodated fractions and crude oil contaminated surface water to freshwater organisms using in vitro and in vivo approaches.

Knowledge regarding the potential impacts of crude oil on endocrine signaling in freshwater aquatic vertebrates is limited. The expression of selected genes as biomarkers for altered endocrine signaling was studied in African clawed frog, Xenopus laevis, tadpoles and juvenile Mozambique tilapia, Oreochromis mossambicus, exposed to weathered bunker and unweathered refinery crude oil water accommodated fractions (WAFs). In addition, the expression of the aforementioned genes was quantified in X. laevis tadpoles exposed to surface water collected from the proximity of an underground oil bunker. The (anti)estrogenicity and (anti)androgenicity of crude oil, crude oil WAFs, and surface water were furthermore evaluated using recombinant yeast. Thyroid hormone receptor beta expression was significantly down-regulated in X. laevis in response to both oil WAF types, whereas a further thyroid linked gene, type 2 deiodinase, was up-regulated in O. mossambicus exposed to a high concentration of bunker oil WAF. In addition, both WAFs altered the expression of the adipogenesis-linked peroxisome proliferator-activated receptor gamma in X. laevis. The crude oil and WAFs exhibited antiestrogenic and antiandrogenic activity in vitro. However, O. mossambicus androgen receptor 2 was the only gene, representing the reproductive system, significantly affected by WAF exposure. Estrogenicity, antiestrogenicity, and antiandrogenicity were detected in surface water samples; however, no significant changes were observed in the expression of any of the genes evaluated in X. laevis exposed to surface water. The responses varied among the 2 model organisms used, as well as among the 2 types of crude oil. Nonetheless, the data provide evidence that crude oil pollution may lead to adverse health effects in freshwater fish and amphibians as a result of altered endocrine signaling. Environ Toxicol Chem 2017;36:1330-1342. © 2016 SETAC.

Eco-epidemiological and pathological features of wildlife mortality events related to cyanobacterial bio-intoxication 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.

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.

The potential of selected macroalgal species for treatment of AMD at different pH ranges in temperate regions.

The metal bioaccumulation potential of selected macroalgae species at different pH ranges was study for usage as part of a possible secondary passive acid mine drainage (AMD) treatment technology in algae ponds. Two separate studies were conducted to determine the suitability of macroalgae for passive treatment when metabolic processes in macrophytes and microorganisms in constructed wetlands decrease during winter months. In the field study, the bioconcentration of metals (mg/kg dry weight) measured in the benthic macroalgae mats was in the following order: site 1. Oedogonium crassum Al > Fe > Mn > Zn; site 2. Klebsormidium klebsii, Al > Fe > Mn > Zn; site 3. Microspora tumidula, Fe > Al > Mn > Zn and site 4. M. tumidula, Fe > Mn > Al > Zn. In the laboratory study, cultured macroalgae K. klebsii, O. crassum and M. tumidula isolated from the field sampling sites were exposed to three different pH values (3, 5 and 7), while bioaccumulation of the metals, Al, Fe, Mn and Zn and glutathione S-transferase (GST) activity were measured in the different selected algae species at a constant water temperature of 14 °C. Bioaccumulation of Al was the highest for O. crassum followed by K. klebsii and M. tumidula (p < 0.0001). From the study it was evident that the highest metal bioaccumulation occurred in the macroalgae O. crassum at all three tested pH values under constant low water temperature.

The impacts of neutralized acid mine drainage contaminated water on the expression of selected endocrine-linked genes in juvenile Mozambique tilapia Oreochromis mossambicus exposed in vivo.

Acid mine drainage (AMD) is a global environmental concern due to detrimental impacts on river ecosystems. Little is however known regarding the biological impacts of neutralized AMD on aquatic vertebrates despite excessive discharge into watercourses. The aim of this investigation was to evaluate the endocrine modulatory potential of neutralized AMD, using molecular biomarkers in the teleost fish Oreochromis mossambicus in exposure studies. Surface water was collected from six locations downstream of a high density sludge (HDS) AMD treatment plant and a reference site unimpacted by AMD. The concentrations of 28 elements, including 22 metals, were quantified in the exposure water in order to identify potential links to altered gene expression. Relatively high concentrations of manganese (~ 10mg/l), nickel (~ 0.1mg/l) and cobalt (~ 0.03 mg/l) were detected downstream of the HDS plant. The expression of thyroid receptor-α (trα), trß, androgen receptor-1 (ar1), ar2, glucocorticoid receptor-1 (gr1), gr2, mineralocorticoid receptor (mr) and aromatase (cyp19a1b) was quantified in juvenile fish after 48 h exposure. Slight but significant changes were observed in the expression of gr1 and mr in fish exposed to water collected directly downstream of the HDS plant, consisting of approximately 95 percent neutralized AMD. The most pronounced alterations in gene expression (i.e. trα, trß, gr1, gr2, ar1 and mr) was associated with water collected further downstream at a location with no other apparent contamination vectors apart from the neutralized AMD. The altered gene expression associated with the "downstream" locality coincided with higher concentrations of certain metals relative to the locality adjacent to the HDS plant which may indicate a causative link. The current study provides evidence of endocrine disruptive activity associated with neutralized AMD contamination in regard to alterations in the expression of key genes linked to the thyroid, interrenal and gonadal endocrine axes of a teleost fish species.

Environmental health outcomes and exposure risks among at-risk communities living in the Upper Olifants River Catchment, South Africa.

Potential exposure to water and air pollution and associated health impacts of three low-income communities in the Upper Olifants River Catchment, South Africa, was investigated through a cross-sectional epidemiological study comprising a household survey. Water samples were collected and analysed for microbial indicators and pathogens. Ambient air-monitoring included some of the criteria pollutants, as well as mercury and manganese. Associations between environmental exposure and health outcomes were analysed by means of logistic regression. Despite poor water and air quality episodes, the communities' self-perceived health was good with relatively low prevalence of reported health outcomes. Hygiene practices with respect to water collection and storage were often poor, and most likely contributed to the regularly contaminated water storage containers. Community proximity to the polluted stream was associated with increased prevalence in adverse health outcomes. This paper reports on preliminary results and additional multivariate analyses are necessary to further understand study results.

Bioaccumulation of aluminium and iron in the food chain of Lake Loskop, South Africa.

Concentrations of total aluminium (Al) and iron (Fe) were determined in Lake Loskop over a period of four months in 2009 in samples of phytobenthos, phytoplankton, macroinvertebrates, amphibians and fish. The highest concentrations of Al and Fe were measured in the filamentous algae Spirogyra fluviatilis (Hillse) and Spirogyra adanata (Kütz), (Al=18,997.5mgkg(-1) dry weight and Fe=22,054.2mgkg(-1) dry weight) in the riverine zone of the lake with a near-neutral water average pH of 7.3. However, a negative correlation exists between the Al and Fe concentrations measured in the filamentous algae in comparison with the corresponding concentrations of these elements in the water column of the riverine zone. The Al concentrations in the macroinvertebrate families collected ranged from 140.6 to 385.7mgkg(-1) dry weight, with the highest values measured for Al and Fe in the family Gomphidae (385.7 and 1710.0mgkg(-1) dry weight, respectively) in comparison to other macroinvertebrate families sampled. Al and Fe concentrations (2580 and 10,697mgkg(-1) dry weight) in the stomach contents of adult Oreochromis mossambicus fishes were much higher in comparison with adult Micropterus salmoides fishes (98.5 and 439.6mgkg(-1) dry weight), respectively. In all cases of dissected fish species either white or yellow body fat was observed, thus in none of the samples both type of body fats occurred simultaneously. The concentrations of total Al and Fe in the different organs of O. mossambicus were along a mean sequence of intestine>yellow body fat>brain>gills>liver>heart>white body fat, while the mean sequence of total Al and Fe in M. salmoides was: intestine>gills>liver>heart>brain>white body fat. From the levels of Al detected in the yellow body fat of the studied fish species O. mossambicus, we suggest that this phenomenon may be related to the feeding habits of this species. Furthermore, the intake of certain species of phytobenthos by O. mossambicus could have played a role in the bioaccumulation of Al in the food chain and the possible development of pansteatitis in predators at higher trophic levels.

Phytobenthos and phytoplankton community changes upon exposure to a sunflower oil spill in a South African protected freshwater wetland.

The occurrence of a sunflower oil spill in 2007 in the Con Joubert Bird Sanctuary freshwater wetland, South Africa, inhibited the growth of sensitive phytoplankton species and promoted that of tolerant species. The algal divisions Chlorophyta and Euglenophyta were well represented in the sunflower oil contaminated water, especially the species Euglena sociabilis, Phacus pleuronectes and Chlamydomonas africana. Young and mature resting zygotes of Chlamydomonas africana were recorded in high abundance at all the sunflower oil contaminated sampling sites. The phytobenthos diversity and abundance were significantly suppressed and negatively associated with low Dissolved Oxygen concentrations and the negative redox potential of the bottom sediment. At the intracellular level, phytoplankton chlorophyll a and b concentrations as physiological variables were more sensitive indicators of the adverse effects of sunflower oil than the 72 h Selenastrum capricornutum algal bioassay conducted.

Identification of toxigenic Microcystis strains after incidents of wild animal mortalities in the Kruger National Park, South Africa.

The eutrophic process potentially caused by a high urine and faecal load resulting from an unusually high hippopotamus (Hippopotamus amphibious) density in the Nhlanganzwane Dam, Kruger National Park, South Africa, triggered a chain of events characterised by an increase in the growth of primary producers (Microcystis aeruginosa). This increase in M. aeruginosa biomass was followed by bio-intoxication incidents in wild animals. In this study, we determine if a M. aeruginosa bloom with a total microcystin level of 23,718microgl(-1) have been responsible for mortalities of megaherbivores in the Nhlanganzwane Dam. We further use microcystin molecular markers derived from the mcy gene cluster to identify potentially toxigenic environmental Microcystis strains in the dam during the occurrence of animal intoxications. The estimated total microcystin-LR daily intake by an adult male white rhinoceros (Ceratotherium simum) from cyanobacterial-contaminated water of the dam during the toxic event was an order of magnitude higher (754.29microgkg(-1)bw) in comparison with the lowest observed adverse effecting level (LOAEL) value measured for pigs in a previous study by other authors. In this study 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 M. aeruginosa.