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• Mallomonas corymbosa, M. kenyana and M. porte-ferreae were found in the Vaal River, South Africa. • Cell morphology and geographical distribution of each species are presented. • Water quality of the Vaal river at the time of sampling is presented. • The finding of M. corymbosa represents the first record of this species in Africa. • M. kenyana, a tropical/subtropical species, were found in temperate regions in South Africa. This paper reports on the presence of three Mallomonas species (Phylum Ochrophyta) in the Vaal River, South Africa. Scanning electron microscope observations of entire cells with intact scales and bristles allowed accurate identifications of M. corymbosa, M. kenyana and M. portae-ferreae. Descriptions and dimensions of each of the three species are given, their geographical distribution is discussed and physico-chemistry of the water at the time of their finding is presented. M. corymbosa was recorded for the first time in Africa, expanding its known geographical distribution to an additional continent. The climatic preferences of the tropical and subtropical species, M. kenyana were extended to temperate regions in South Africa. These species were present under eutrophic to hypertrophic conditions, a water temperature of 25.4 °C, neutral to slightly alkaline water (pH 7.25) and a conductivity value of 440 µS/cm. [ABSTRACT FROM AUTHOR]

Diatoms are siliceous micro-algae and have been used with increasing frequency as bioindicators in aquatic ecosystems. Typically, European diatom indices have been modified and augmented with data on taxa endemic to and commonly found in other parts of the world. In order to further test the application of diatom indices, water quality and diatom sampling were performed in the Bloukrans River system, Eastern Cape Province of South Africa. Nine sites with contrasting water quality were sampled along the length of the river in February, May and July 2018. Multivariate statistical analysis (Canonical Correspondence Analysis) was employed to elucidate spatiotemporal differences in diatom community structure. Canonical correspondence analysis indicated that differences in diatom community assemblages were best explained by dissolved oxygen, temperature, nitrate, conductivity and phosphate. Diatom-based indices incorporated in OMNIDIA software were also applied to assess the integrity of the water quality as indicated by diatom communities. Several foreign indices (e.g. the trophic diatom index (TDI), biological diatom index (BDI)) and the South African Diatom Index (SADI) were used in the study. The SADI demonstrated that the Bloukrans River was impacted and had significant correlations with water quality variables (p <.05). We therefore recommend the wider use of the SADI as an indicator of water quality conditions in South African lotic systems. • Anthropogenic perturbations in Bloukrans River system can be assessed using diatom indices and multivariate analysis. • High levels of nitrate, phosphate and conductivity were recorded in downstream urban sites. • Patterns of diatom assemblages were different between sites. • The South African Diatom Index (SADI) showed significant strong correlations with all water quality variables considered. • The South African Diatom Index (SADI) is also applicable for the Eastern Cape river systems. [ABSTRACT FROM AUTHOR]

Phytoplankton is an important role player in the ecology of rivers and streams, and sensitive to changes in water quality. This study aimed to determine how pollution influenced phytoplankton composition in two streams and to confirm the dominant phytoplankton Classes and genera at each stream as indicators of the water quality. The water from the Vaal River in the Middle Vaal Catchment of South Africa is heavily polluted by the time it is abstracted for treatment by Midvaal Water Company. The Koekemoerspruit is an upstream tributary of the Vaal River and is considered a possible source of pollution. Physical and chemical water quality data were collected for 21 variables together with phytoplankton samples at five strategically selected sites over a two-year period (November 2012 to October 2014). The Vaal River showed extreme total chlorophyll concentrations associated with high pH levels compared to the Koekemoerspruit in which high ammonia, nitrate and nitrate and orthophosphate concentrations confirmed severe organic pollution. A total of 86 algal genera were identified and grouped into seven phytoplankton classes. Average phytoplankton cell concentrations of 1,410,069 cells/mL and 417,931 cells/mL were determined for the Vaal River and the Koekemoerspruit respectively. A redundancy analysis summarised and confirmed that water quality had a definite effect on the phytoplankton assemblages for the Vaal River and the Koekemoerspruit (p -value of 0.08). Both streams were eutrophic but Chlorophyceae dominated in the Vaal River (49%) and Cyanophyceae were predominant in the Koekemoerspruit (44%). The dominant presence of phytoplankton genera such as Scenedesmus spp. (42%) and Nitszchia spp. (84%) confirmed the main water quality characteristics of the two streams. • Comparison of 2 differentially polluted streams, Vaal River and Koekemoerspruit. • Significant correlation between physical chemical parameters and phytoplankton taxa. • Chlorophyceae (Scenedesmus spp) dominated in Vaal River. • Cyanophyceae (Nitszchia spp) dominated in Koekemoerspruit. [ABSTRACT FROM AUTHOR]

Monitoring of wetland ecosystems is crucial as these ecosystems provide numerous services and resources to both humans and the biota found therein. Wetlands are characterised by variations in inundation time and depth and therefore it is often difficult to make use of invertebrates and fish as biological indicators. Diatoms may be used for monitoring of wetland ecosystems as they are widely distributed, are microscopic with few habitat restrictions, communities are species rich and they respond rapidly to environmental changes. Very little information is available on wetland diatom communities in South Africa. Wetland ecosystems include Ramsar sites such as Lake Sibaya which faces increased forestry and rural development within the lake's catchment area. Therefore, this study aimed to determine the diatom community structure of Lake Sibaya and its response to changes in water quality. Water and diatom samples were collected from four sites in Lake Sibaya during August 2015, December 2015 and February 2016. All samples were collected and analysed according to standard methodologies. From the results it was clear that the lake had a lower diatom diversity than that described in a previous study in 1966, with Cocconeis placentula, Gomphonema sp., Epithemia adnata and Nitzschia sp. being the dominant taxa. Both the diatom community structure and measured water quality parameters showed the lake to be nutrient enriched. However, as nutrients accumulate in wetlands it is unknown whether the increased nutrients arise from anthropogenic disturbances or natural sources. • First study completed on the diatom diversity in Lake Sibaya since 1979. • A total of 59 diatom species were identified over three surveys. • Measured water quality indicated Lake Sibaya as nutrient enriched. • Diatom indices and community structure indicated the lake as nutrient enriched. • Lake Sibaya probably has increased nutrients due to forestry, rural development and the development of Mseleni town. [ABSTRACT FROM AUTHOR]

Microplastic (MPs) pollution has become a subject of environmental concern due to its wide ubiquity in the environment. Microplastics are possible sources of other hazardous chemicals to aquatic organisms due to their composition and sorption properties. In this study, MPs occurrence in water and sediment samples of the Plankenburg River, Western Cape, South Africa was investigated. The physicochemical characterization of the river water was done onsite. 30 L water samples were collected and filtered in 10 L triplicates through a 250 μm mesh onsite using a metal bucket. An additional 12 L sample was collected and filtered in 4 L triplicates through 20 μm mesh in the laboratory. The extraction of MPs from water in the laboratory was by density separation. Sediment samples were also collected at the selected sites, oven-dried and microplastics in the laboratory. Sampling was conducted over four seasons – spring, summer, autumn, and winter. Microplastics were classified by visual observation and Fourier Transform Infrared Spectroscopy (FTIR-ATR). The seasonal distribution of MPs in the surface water samples varied across all sites. However, spring samples had the highest MPs occurrence (5.13 ± 6.62 MP/L) and the least, in autumn (1.52 ± 2.54 MP/L). The MPs in sediment samples were observed in spring (1587.50 ± 599.32 MP/kg). Fibres were the most dominant microplastic particle type (shape), with a size range of 500–1000 μm at the different sites. The infrared spectroscopic analysis confirmed the dominant polymer type to be polyethylene. This study provides an understanding of the microplastic occurrence in the Plankenburg River system and gives a baseline for future monitoring and assessment of water and sediment in the South African freshwater systems. [Display omitted] • The first investigation of microplastics in the Plankenburg River was reported. • Polyethylene was the main polymer type in the Plankenburg River. • Fibres were the most dominant shapes of microplastic particles. • Anthropogenic activities contributed to microplastic pollution. [ABSTRACT FROM AUTHOR]

There has been a recent increase in water quality problems in South Africa. The monitoring of water resources is important for the continued management of water resources. The use of artificial mussels (AMs) as passive sampling devices in the monitoring of metals within a freshwater system was evaluated in a recent field study. Correlation testing was conducted between the AMs and Melanoides tuberculata for As, Cd, Cr, Co, Cu, Pb, Mn, Ni, U, V and Zn. It was found that a positive significant correlation exists between AMs and M. tuberculata with regards to As, U, and Co accumulations. The trend of metal accumulation between AMs and M. tuberculata were found to be similar for all of the metals tested. Site 2 which is located close to a gold mine, was found to have the highest metal concentrations in this study. This study confirms the hypothesis that AMs can be used as a useful tool for monitoring metals in freshwater. [ABSTRACT FROM AUTHOR]

• We evaluated the role of mussels in enhancing coastal water quality. • The study took place in False Bay, Southern Africa's largest natural bay. • Most environmental indicators showed a 2-way gradient: onshore-offshore, west-east. • Pollution inputs were mainly detected on one side of the bay. • Coastal circulation and intertidal filter feeders mitigated anthropogenic inputs. Nearshore water quality can be highly impacted by anthropogenic activities ongoing along the coast, the effects of which on natural environments can be permanent and irreversible, with consequences for ecosystem biodiversity and functioning, as well as for associated services. Benthic filter feeders (e.g., mussels) provide several services for coastal regions, including improving water quality by reducing eutrophication, being a major source of food for humans, and as a habitat-forming species. Here, we seek to understand the role of benthic filter feeders in enhancing water quality in an urban coastal system in order to assess their role as ecosystem service providers and how they should be included in ecosystem-based evaluations. Using as a model False Bay, South Africa's largest natural bay and a socio-economic hotspot, this multidisciplinary study was designed to identify possible pollution sources to a highly-urbanised coastal region, assess their effects on several biological and biogeochemical parameters, and evaluate the role of mussels in mitigating these anthropogenic inputs. We consider several sources of pollution, including nutrient loading from wastewater and river outflows, heavy metals, and aerosol deposition. We find that pollutant inputs are largely attenuated by the circulation of the bay and by the presence of filter feeders that bioaccumulate contaminants, thereby removing them from coastal waters. Our work thus emphasizes the potential for mussels and natural abiotic processes to ameliorate anthropogenic impacts, although these mitigation strategies are not without environmental risk. We recommend that such information should be included in national assessments used to develop appropriate strategies and policies for coastal environmental management and conservation. [ABSTRACT FROM AUTHOR]

Research on the flow of virtual water associated with agricultural crop production and trade has focussed almost entirely on water quantity. It is pertinent to consider and quantify the opportunity costs in terms of reduced water quality associated with crop production. This paper investigates the impacts of water quality on virtual water trading by creating a proxy for water quality impacts by calculating the amount of water required to dilute nonpoint-source agrochemical inputs to relevant water quality guideline values. The quantity of water required for dilution of five agrochemicals (two nutrients; nitrogen and phosphorus and three insecticides; azinphos-methyl, chlorpyrifos and endosulfan) was estimated for five crops in South Africa (maize, wheat, sugar cane, citrus and cotton) and compared to consumption of irrigation water (blue water) and rainfall (green water) for the same crops. Results indicate that the volume of water required for dilution is similar to the total sum of green and blue water required for crop production, but significantly greater than blue water use (irrigation use). For all crops phosphorus losses require greater amounts of water for dilution than for nitrogen, while pesticides result in the greatest water quality use. Estimates of water quality use are based on assumptions for a number of input variables (i.e. fertilizer application rates, percentage loss of agrochemicals from cropped areas). A Monte Carlo analysis (5000 iterations) was run to randomly select input variables from within defined ranges. Water quality use was calculated and expressed as a factor of blue water use. For all crops the average factor indicated that the volume of water required for dilution of all agrochemicals was greater than that required for irrigation. The results of this study clearly indicate that the impacts of agriculture on water quality need to be considered in virtual water trading scenarios. The incorporation of a method to predict impacts on... [Copyright &y& Elsevier]

South African surface waters are subject to various forms of pollution. Recent findings in aquatic systems suggest an association exists between yeast diversity, chemical pollutants and land coverage, which are important water quality determinants. Yeast abundance and diversity, as well as antifungal agents in two river systems in South Africa, were investigated and related to the existing land coverage. Yeast abundance and diversity were determined from environmental DNA by quantitative polymerase chain reaction and next-generation sequencing, respectively, of the 26S ribosomal ribonucleic acid (rRNA) gene. Antifungal agents were qualitatively and/or quantitatively detected by ultra-high-pressure liquid chromatography-mass spectrometry. Analyses of 2 031 714 high-quality 26S rRNA sequences yielded 5554 amplicon sequence variants (ASVs)/species. ASV richness and Shannon-Wiener index of diversity reflected the southward flow of the river with higher values observed downstream compared to the upstream. Fluconazole concentrations were quantifiable in only two samples; 178 and 271 ng L−1. Taxonomically, at least 20 yeast species were detected, including the dominant Candida tropicalis , Cryptococcus spp. as well as the lesser dominant Bensingtonia bomiensis , Fereydounia khargensis, Hericium erinaceus , Kondoa changbaiensi , Pseudozyma spp. and Sphacelotheca pamparum. The two dominant species are known opportunistic pathogens which had antifungal resistant traits in previous studies from the same rivers and therefore is a public health threat. The present study provides further evidence that yeasts should be included as part of water quality parameters, especially in developing countries where much of the population are economically disadvantaged, and also immunocompromised due to age and disease. • Diversity, abundance of yeast and antifungals determined via NGS, qPCR and UHPLC-MS. • Candida tropicalis , a potential pathogen, was relatively most dominant. • Fluconazole concentration was positively correlated to mining and urban activities. • Correlation between C. tropicalis and fluconazole suggest fluconazole-resistance. [ABSTRACT FROM AUTHOR]

The legacy of the inequitable water policy under apartheid continues to impact water services in economically less developed and rural areas in South Africa. Previous studies typically examine this relationship either by using aggregated data at the national level for large-scale research or by using data collected at the provincial or municipal level only for a specific locality. This study attempts to perform nationwide analysis using fine-scale data to give a spatial representation of the efficacy of water policies in South Africa. We used satellite night-time light data as a proxy of economic development and surface water quality at a quaternary water area level to investigate any income or racial inequality regarding water pollution, controlling for the spatial dependency of the observations. We found a spatial discrepancy in the relationship between water quality and economic development: economic development improves water quality in western provinces and in former white-dominated areas, whereas it generally degrades water quality in other regions of the country. These results suggest the inability of the government to equitably provide the same standards of water policies nationwide and the presence of inequitable policies as legacies of apartheid at the lowest level of water policy implementation. [ABSTRACT FROM AUTHOR]

• A new, continental-scale freshwater assessment tool, African Dragonfly Biotic Index. • 604 African dragonfly species are evaluated. • This index determines deterioration or recovery of a freshwater site. • It also compares freshwater quality at different sites. • The index is a foundation for developing other national Dragonfly Biotic Indices. African freshwater ecosystems are increasingly being impacted by humans, requiring an effective tool to assess these impacts for future conservation action. Such a tool, the Dragonfly Biotic Index (DBI), was earlier developed to assess the quality of South Africa's freshwater ecosystems and is based on combining the scores of three sub-indices (geographical distribution, threat status, and habitat sensitivity) for each South African dragonfly species. The sum of the DBI scores for all the species recorded at assessed sites indicates the relative quality of these sites. The International Union for the Conservation of Nature/Species Survival Commission (IUCN/SSC) has assessed the threat status of certain aquatic taxa in Africa, including dragonflies. These assessments, coupled with the latest information on the geographical distribution of each species, makes it possible here to geographically expand the South African DBI into a continental-scale assessment index (the African Dragonfly Biotic Index (ADBI)) by adapting the South African DBI sub-indices. We develop this continental index here. However, there are challenges when undertaking an assessment at the continental scale compared to a national scale. In particular, the habitat sensitivity sub-index of the South African DBI is a relative, quantitative measure based on numbers of individual dragonflies recorded from natural versus human-modified or artificial freshwater systems. While the data for the two sub-indices, species' geographical distribution and Red List threat statuses, are available across the continent, this is not the case for the habitat sensitivity sub-index at this large spatial scale. This meant that an alternative sub-index measure was required. We overcame this challenge by exploring an alternative sub-index, i.e. the 'species vulnerability sub-index', based on knowledge of the vulnerabilities of the species to certain types of landscape transformation. Then, the species vulnerability sub-index scores were calculated and combined with the geographical distribution and Red List threat status sub-index scores to develop ADBI scores for a core of 604 dragonfly species with adequate data across the African continent. These ADBI scores provide a workable framework and baseline for determining freshwater quality, both lotic and lentic, relative to human disturbance at a continental spatial scale. The ADBI enables the monitoring of quality changes, for better or worse, over the continent in years to come. Overall, the ADBI also has the potential to help identify threats to, and sensitivities of, African freshwater ecosystems, leading to conservation action. [ABSTRACT FROM AUTHOR]

• Urbanisation of riverine landscapes is a major threat to river ecosystems. • Urban pollution signature and sensitive traits were identified. • Signature traits/preferences: a large body size and preference for vegetation. • Sensitive traits include swimming, and grazing. Urbanisation of riverine landscapes is a major threat to river ecosystems because of the ecological consequences of the so called urban stream syndrome. Taxonomically, certain macroinvertebrate metrics such as the diversity of species of Ephemeroptera, Plecoptera and Trichoptera (EPT) are known to be sensitive to urban pollution, whereas chironomids and oligochaetes are relatively tolerant. Trait correlates of such taxonomic metrics are yet to be established even though traits are less constrained by geographical differences. Using the Swartkops as a case study of a river receiving urban pollution, the pattern of trait distribution in relation to a gradient of urban pollution was examined, and urban pollution signature and sensitive traits identified. Macroinvertebrates and physico-chemical analysis were undertaken over a period of three years between August 2009 and September 2012 at one control site and three impacted downstream sites. Seven traits resolved into 32 trait attributes including body size, respiration, body shape, mobility, biotope preference, preferred food, and feeding habits were fuzzy coded and analysed using RLQ and fourth-corner analyses. Of the 32 trait and ecological attributes, four, including large body size (>20 to 40 mm), animal materials as preferred food, predation and a preference for vegetation biotope, which were associated with the impacted sites, and were also significantly positively correlated with at least one physico-chemical indicator of increasing urban pollution were deemed signature traits. Three traits, swimming, fine particulate organic matter and grazing, associated with the control site, which showed significant negative correlations with at least one physico-chemical indicator of increasing urban pollution were identified as sensitive traits. The results indicate that urban pollution differentially influenced macroinvertebrate traits, with the identification of pollution signature and sensitive traits seen as an important step towards the development of trait-based indices for riverine monitoring of urban pollution effects. [ABSTRACT FROM AUTHOR]