A stable isotope analysis of the dietary patterns of the aquatic apex predator, the African tigerfish (Hydrocynus vittatus).

Stable isotope analyses, specifically δ13 C and δ15 N, are useful tools increasingly used to understand ecosystem function, food web structures, and consumer diets. Although the iconic tigerfish Hydrocynus vittatus is regarded as an apex predator in southern African freshwater systems, little information is available regarding their feeding behavior and how this may change with growth or differ between ecosystems, with most information stemming from stomach content analyses (SCA). The aim of the present study was to address this lack of information through a baseline study of the diet of large and small tigerfish in various lentic and lotic ecosystems in South Africa using stable isotope methods. Fish and various food web components and food sources were collected from two river and two lake ecosystems in South Africa. The δ13 C and δ15 N values for all samples were determined and multivariate analyses and Bayesian analytical techniques applied to determine the feeding ecology of H. vittatus and how this may differ with size and habitat type. Analyses revealed a substantial difference in the type and abundance of food sources contributing to the diet of H. vittatus between ecosystems, most prominently between the lotic systems, where less dietary specialization was observed, and lentic systems where more specialization was observed. Furthermore, there was a distinct difference in diet between small and large tigerfish, especially in the lotic system, indicating an ontogenetic diet shift as tigerfish grow and further supporting previous SCA studies. This is the first study of its kind on the African continent for H. vittatus and the findings illustrate the value of stable isotope analysis in providing in-depth information into the feeding ecology of consumers and how this may differ between size classes and habitat types.

Morphological and molecular characterisation of Alella igillimpethu n. sp. (Copepoda: Siphonostomatoida: Lernaeopodidae) parasitising the southern African endemic intertidal klipfish, Clinus superciliosus.

Lernaeopodidae Milne Edwards, 1840, is an ecological and economically important fish parasite family of copepods (Crustacea: Copepoda), consisting of 48 genera with 334 valid species. To date, approximately 17 genera have been documented from both teleost and elasmobranch hosts from South African marine waters. As part of parasitological surveys targeting parasites of the endemic intertidal klipfish, Clinus superciliosus (Linnaeus) (Clinidae) along the South African coast, a species of Lernaeopodidae was discovered on the gills of this host. Alella igillimpethu n. sp. is described from Clinus superciliosus from Langebaan marina on the west coast of South Africa, with a prevalence of 42.1% and mean intensity of 2.9 (ranging from 1-13). Morphological identification was done using light and scanning electron microscopy and the species description was generated with the aid of DEscription Language for TAxonomy (DELTA) software. The mitochondrial cytochrome c oxidase subunit 1 (COI) region, as well as partial 18S and 28S ribosomal RNA genes confirmed the classification within the family Lernaeopodidae. This is the first report of Lernaeopodidae from C. superciliosus, or in fact any member of Clinidae, as well as the first molecular characterisation of any marine lernaeopodid infecting teleost fish from South Africa. This study contributes valuable genetic and morphological data for this copepod family, as well as new host and distribution records.

Element Concentrations in Muscle and Liver Tissue of Two Eel Species from the Incomati River, Mozambique.

Many rural communities in Mozambique get their income from fisheries, as well as consume fish as an inexpensive source of protein. In Mozambique, fish consumption from small-scale fisheries dependent families can range between 60 and 150 kg/person/year. Anguillid eels have important social value to vulnerable local communities in the Incomati Basin. Anguillid eels in the lower Incomati Basin are targeted for consumption, as well as cultural rituals by traditional healers. The aim of the present study was to determine trace element concentrations in environmental matrices, bioaccumulation patterns in muscle and liver tissue of two Anguilla species (Anguilla mossambica and Anguilla marmorata), as well as the chronic health risk these elements pose to regular consumers in the lower Incomati River. Bioaccumulation of elements from the water had a higher effect on both muscle and liver tissues, where only the bioaccumulation of Pb in the sediments played a major role. From the human health risk assessment, Hg pose non-carcinogenic risk, whereas As, Cr, and Ni pose carcinogenic risks.

Using Confocal Microscopy and Pigment Analyses to Detect Adverse Insecticide Effects in non-target Freshwater Diatom species - a proof-of-concept Using Nitzschia palea.

The persistence of insecticides in aquatic environments is a cause of concern and to date hardly any studies have focused on the effects that DDT and deltamethrin have on non-target freshwater diatom communities. The application of diatoms in ecotoxicological studies is well acknowledged and therefore this study used laboratory bioassays to determine the effects that DDT and deltamethrin have on a monoculture of a diatom indicator species, Nitzschia palea. The insecticides affected the morphology of chloroplasts at all exposure concentrations. These effects were a maximum reduction in chlorophyll concentrations (4.8% and 2.3%), cell viability (51% and 42%), and increases in cell deformities (3.6% and 1.6%) following exposure to DDT and deltamethrin respectively. Based on the results we propose that methods, such as confocal microscopy, chlorophyll-α analysis and cell deformities are useful tools in assessing the effects of insecticides on diatoms.

Oxidative stress in the freshwater shrimp Caridina africana following exposure to atrazine.

The toxicity of pesticides to non-target organisms continues to be important in understanding the dynamic interactions between anthropogenic chemicals and ecosystem health. This study assesses biochemical markers to determine the effects that varying concentrations of atrazine (13.1-5557 µg/l) have on the freshwater shrimp, Caridina africana. Exposure and oxidative stress biomarkers were analysed and followed by univariate, integrated biomarker response v2 (IBRv2) and Kendall Tau correlation statistical analyses, to gain insight into the concentration-dependent responses. Oxidative stress biomarkers such as reduced glutathione content (GSH), glutathione-S-transferase activity (GST), superoxide dismutase activity (SOD) and catalase activity (CAT) were significantly correlated with increasing atrazine exposure concentration (p < 0.01). Bimodality has been seen when looking at both the univariate statistically significant differences as well as the IBRv2, with the first peak at 106.8 µg/l and the second peak at 5557 µg/l atrazine. The results indicate that while individual responses may indicate statistically significant differences, using correlation and integrated statistical analysis can shed light on trends in the adaptive response of these.

Regional Scale Risk to the Ecological Sustainability and Ecosystem Services of an African Floodplain System.

The Phongolo floodplain is one of southern Africa's most important systems. In this study, we carried out a regional scale ecological risk assessment to evaluate the risk of multiple stressors associated with the use of the aquatic resources in the floodplain to selected social and ecological endpoints representing its sustainability. The floodplain has undergone significant changes as a result of the impacts of multiple stressors. This includes high risk of impact and threatened sustainability between the Pongolapoort Dam and the Ndumo Game Reserve (NGR). This compares to relatively low risk to the maintenance of the endpoints within the NGR. The reserve provides a protection and refuge function for regional biodiversity maintenance and ecosystem sustainability processes. In the study a range of scenarios were considered and demonstrate that the system will respond to protection measures and or increased resource use options. Should flood reductions or water quality pollution drivers continue on increasing trajectories, the condition of the Phongolo River and floodplain will probably deteriorate into an unacceptable, unsustainable state. Removal of the protection services of the NGR would result in an unsustainable ecosystem and loss of ecosystem services for regional vulnerable African communities. Additional evidence should be obtained from monitoring and research to refine, validate, and update the assessment in an adaptive management context. The risk assessment framework approach implemented in the Phongolo floodplain can contribute to the management of other floodplains ecosystems and the sustainability management of social and ecological attributes and processes of these important ecosystems.

Current Status and Future Prognosis of Malaria Vector Control Pesticide Ecotoxicology and Xenopus sp.

Anurans from the genus Xenopus have long been used as standard testing organisms and occur naturally in tropical and sub-tropical areas where malaria vector control pesticides are actively used. However, literature on the toxic effects of these pesticides is limited. This review analyses the available data pertaining to both Xenopus and the pesticides used for malaria vector control in order to determine the pesticides that have the greatest potential to influence amphibian health while also identifying gaps in literature that need to be addressed. Amphibian diversity has shown the fastest decline of any group, yet there are still voids in our understanding of how this is happening. The lack of basic toxicity data on amphibians with regard to pesticides is an issue that needs to be addressed in order to improve effectiveness of amphibian conservation strategies. Meta-analyses performed in this review show that, at current usage, with the available acute toxicity literature, the pyrethroid pesticide group could hold the highest potential to cause acute toxicity to Xenopus sp. in relation to the other MVCPs discussed, but the lack of data cripples the efficacy with which meta-analyses can be performed and conclusions made from such analyses. Several studies have shown that DDT accumulates in Xenopus sp. from malaria vector control areas, but accumulation of other MVCPs in frogs is still largely unknown. Through this review we hope to encourage future research into the field of amphibian ecotoxicology and to promote the use of the Xenopus standard model in order to build comprehensive datasets that may be used in amphibian conservation.

The role of fish helminth parasites in monitoring metal pollution in aquatic ecosystems: a case study in the world's most productive platinum mining region.

Due to the increasing consumption of platinum (Pt), especially in automobile exhaust catalysts, environmental concentrations of Pt are of emerging concern worldwide. Limited information exists on environmental concentrations, particularly in Pt mining regions, while South Africa is the world's main supplier of Pt. Moreover, other metals are also released as by-products of Pt mining, which might also cause environmental concern. Certain fish parasite taxa have the ability to accumulate metals orders of magnitude higher than their hosts and can be used to reliably detect metals with naturally low abundance. Studies on Pt accumulation in parasite-host systems are limited. Therefore, the aims of the present study were (1) to determine the accumulation of a variety of metals (cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), platinum (Pt), and zinc (Zn)) in helminth fish parasites compared with their hosts from a reference site and an impoundment impacted by Pt mining activities; (2) to assess whether there is a difference between bioaccumulation of metals in infected and uninfected hosts, as well as between hosts with different infection intensities; and (3) to compare the biomarker responses (acetylcholine esterase activity (AChE), metallothionein content (MT), catalase activity (CAT), reduced glutathione content (GSH), malondialdehyde content (MDA), protein carbonyls induction (PC), superoxide dismutase activity (SOD), and cellular energy allocation (CEA)) between infected and uninfected hosts. The cestode Atractolytocestus huronensis accumulated significantly higher concentrations of Cr, Ni, and Pt than their host Cyprinus carpio, while the nematode Contracaecum sp. accumulated significantly higher concentrations of Pt and Zn than their host Clarias gariepinus. Infected fish showed lower metal concentrations compared to uninfected fish, while the parasites had no significant effects on their hosts' biomarker responses. The parasites demonstrated the bioavailability of metals derived from Pt mining activities and their ability to resist its toxic effects. Thus, these parasites are promising sensitive accumulation indicators for Cr, Ni, Pb, and Pt contaminations from Pt mining activities.

Biomarker Responses in the Freshwater Shrimp Caridina nilotica as Indicators of Persistent Pollutant Exposure.

Biomarkers are applied as early warning indicators of organisms' exposure to pollutants. The aim of this study was to utilise a multi-biomarker approach in the freshwater shrimp Caridina nilotica (Decapoda: Atyidae) as indicators of persistent pollutant exposure. A suite of biomarkers was selected to cover oxidative stress and damage, and energetics of the organisms. Five sites, representing an agricultural and pesticide application gradient, were sampled during two flow related hydro-periods in rivers of the Phongolo floodplain, north-eastern South Africa. Cytochrome P450 (CYP) activity was significantly higher in shrimp at sites directly adjacent to regions of increased human activity. Increased oxidative responses, i.e. catalase (CAT; p < 0.01) and protein carbonyl (PC, p < 0.01) were also found at these sites. The energetics biomarker did not show any influence of increased contaminant exposure. We demonstrated that the biomarkers of exposure (CYP) and effect (CAT, PC) were suitable to detect effects of stressors, probably persistent pollutants.

Assessing predator-prey interactions in a chemically altered aquatic environment: the effects of DDT on Xenopus laevis and Culex sp. larvae interactions and behaviour.

Behavioural assays are used as a tool to understand ecotoxicological effects on organisms, but are often not applied in an ecologically relevant context. Assessment of the effect of chemical contaminants on behaviours relating to fitness and trophic interactions for example, requires incorporating predator-prey interactions to create impact assessments. Dichlorodiphenyltrichloroethane (DDT) is a controlled substance but is still regularly used as a form of mosquito control. There is little explicit information on the effect of DDT on animal behaviour and the consequent effects upon trophic interactions. This study uses a 3 × 2 factorial design to assess the feeding behaviour of Xenopus laevis toward Culex sp. larvae when supplied with different prey cues. We also assess the behavioural responses of mosquito larvae when supplied with no threat cue and predator threat cues when exposed to 0 µg/L, 2 µg/L and 20 µg/L DDT. There was a significant "DDT exposure" x "prey cue" interaction whereby DDT significantly decreased the foraging behaviour of X. laevis towards live prey cues, however there was no effect of DDT on X. laevis response to olfactory prey cues. Dichlorodiphenyltrichloroethane exposure caused mosquito larvae to appear hyperactive regardless of DDT concentration. Mosquito larvae anti-predator response was significantly dampened when exposed to 2 µg/L DDT, however when exposed to 20 µg/L the anti-predator responses were not impaired. Our results indicate a complex interplay in trophic interactions under DDT exposure, wherein effects are mediated depending on species and concentration. There are possible implications regarding reduced anti-predator behaviour in the prey species but also reduced foraging capacity in the predator, which could drive changes in ecosystem energy pathways. We demonstrate that in order to quantify effects of pesticides upon trophic interactions it is necessary to consider ecologically relevant behaviours of both predator and prey species.

Biomarkers in tigerfish (Hydrocynus vittatus) as indicators of metal and organic pollution in ecologically sensitive subtropical rivers.

Studies have shown high levels of contamination of both metals and organochlorine pesticides (OCPs) in aquatic systems of the world renowned Kruger National Park, South Africa. With effects evident in top predators, including, unexplained Crocodylus niloticus deaths and organ level and histological changes in Hydrocynus vittatus. A suite of biomarkers reflecting exposure and were selected to evaluate biological responses of H. vittatus to anthropogenic stressors as well as to evaluate whether the chosen suite of biomarkers could successfully distinguish between the different pollution profiles present in the selected rivers. During this study a clear relationship was found between exposure to environmental contaminants and the concomitant responses of H. vittatus to these stressors. The ensuing biomarker responses indicated that there is a physiological attempt to deal with, and mitigate the deleterious effects that metals and OCPs may induce. In the Luvuvhu River there is a clear indication in H. vittatus of the stimulation of anti-oxidant protective mechanisms in response to internal OCP exposure. This is reflected by the increasing cytochrome P-450, superoxide dismutase, and more specifically reduced glutathione, which resulted in decreased lipid and protein breakdown (reflected in decreased lipid peroxidation and protein carbonyl levels). Consequently H. vittatus populations of the Luvuvhu River are under greater cumulative stress and this is reflected in the lower energy budgets. Our results further show the integrated application value of the current suite of biomarkers in assessing responses of subtropical fish to metal and OCP exposure as the entire suite of biomarkers when used in conjunction were able to explain 100% of the variation in the data.

Linking organochlorine exposure to biomarker response patterns in Anurans: a case study of Müller's clawed frog (Xenopus muelleri) from a tropical malaria vector control region.

Organochlorine pesticides are highly persistent in aquatic ecosystems. Amphibians, specifically anurans, play an intricate part in the aquatic food web, and have very permeable skin which makes them prone to bioaccumulation of persistent pollutants. In this study the bioaccumulation of various legacy organochlorine pesticides (OCPs)-including dichlorodiphenyltrichloroethane (DDT), currently used for malaria vector control (MVC)-was assessed along with a set of biomarker responses in Müller's clawed frog Xenopus muelleri collected from the lower Phongolo River floodplain in South Africa. Possible relationships between bioaccumulation and biomarkers (of exposure, oxidative stress biomarkers, and cellular energy allocation) alongside their temporal changes were investigated. The OCP concentrations showed a significant increase over time for the duration of the study. The increase correlated negatively with rainfall from the region. DDT levels were well below expected effects levels with p,p-DDE being the main contributing metabolite. The results of this study indicate OCPs actively accumulate at sub-lethal levels in aquatic frogs from the study area, while showing possible relations towards some of the biochemical stress responses measured. Most notable were negative relationships indicated between p,p-DDE and acetylcholinesterase, malondialdehyde, and carbohydrates and protein energy availability. Levels of DDT were not found to be significantly higher than other legacy pesticides in the frog tissue, although evidence of newly introduced DDT in the frog tissue was found. Further investigation about sub-lethal effects of these pesticides on anurans is required to gain better insight into their full impact on animal livelihood.

Metal concentrations in Hydrocynus vittatus (Castelnau 1861) populations from a premier conservation area: Relationships with environmental concentrations.

Metals are known to have deleterious effects on aquatic ecosystems, so monitoring the bioaccumulation of these pollutants is important for the assessment of potential impacts. The aim of the study was therefore to determine the degree to which aquatic biota in selected rivers of the world renowned Kruger National Park (KNP) are exposed to metals entering from the catchments outside the KNP and to determine how these metal levels reflect what is occurring within the environment. Many of these rivers have never previously been assessed and those which have, have not been assessed within the past two decades. Tigerfish (Hydrocynus vittatus) is an economically important apex predator and was selected as the bioindicator for this study. Fish were sampled from the KNP sections of the Luvuvhu, Letaba and Olifants Rivers during the high and low flow periods from 2009 to 2011. The analysis of various metals from the aforementioned systems revealed spatial and temporal related variation in metal level patterns of the chosen bioindicator, with concentrations in fish from the Olifants River>Letaba River>Luvuvhu River and 2009>2010>2011. Although there were differences between rivers, metal concentrations were comparable and indicate that all of the studied KNP rivers, even those considered to be in a natural state are affected to some degree by anthropogenic activities. However, concentrations found during this study were much lower than previous studies in the area, as well as contaminated sites across the world, but were higher than concentrations in fish from contaminated sites in the Vaal River, South Africa. Bioaccumulated metals showed no correlation to metals in the water column, but some were correlated to sediment metal concentrations and the contamination and bioavailability of these metals within the sediments. This is of concern when managing the water resources of the conservation area since the contaminants enter the park from outside the borders and pose potential risks to the mandated conservation of aquatic biota within the KNP.

Influence of Mining Pollution on Metal Bioaccumulation and Biomarker Responses in Cave Dwelling Fish, Clarias gariepinus.

Cave 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 Al.

Distribution, abundance, population structures, and potential impacts of the invasive snail, Tarebia granifera in aquatic ecosystems of north-eastern South Africa.

Aquatic ecosystems globally have been invaded by molluscs. Tarebia granifera is a highly successful invader, often becoming the dominant aquatic invertebrate species in an invaded ecosystem. Resultingly, it has been suggested that T. granifera may have severe negative impacts on these invaded ecosystems. Limited information is available regarding the population structures and densities of T. granifera, particularly in invaded countries such as South Africa, and information on this could assist in developing management and control strategies for this invasive species. The present study aimed to assess the current distribution, densities, and population structures of T. granifera in invaded habitats on the Limpopo and Phongolo River systems in South Africa. This was accomplished by collecting aquatic molluscs from sites across these systems. Water quality parameters were measured at each site and water samples were collected for chemical nutrient analyses. The density of snails was determined for each site and the population size and structure as well as birth rate was calculated for T. granifera. Tarebia granifera was found to be the dominant molluscan species in habitats where it was present and all size classes from newborn to mature adults were found throughout at some of the highest densities globally. Worryingly, native molluscan species, were often absent or in much lower densities than reported in literature at sites where T. granifera was present, suggesting a negative effect on the native molluscan density and diversity. Contrary to most previous studies, there were no significant correlations between T. granifera and the selected water quality parameters. Higher densities and newborn recruitment of T. granifera were observed in the spring than in autumn, likely in response to shifts in environmental conditions. This study provides crucial insights into the population structure, densities, and impacts of T. granifera in invaded habitats, particularly for relatively newly invaded regions such as southern Africa.

Effects of river regulation on aquatic invertebrate community composition: A comparative analysis in two southern African rivers.

While natural floods play a crucial role in shaping the composition of aquatic communities, the most rivers worldwide are regulated or dammed for anthropogenic purposes, resulting in alterations to the biological and chemical composition of these ecosystems. Studies have demonstrated various negative effects of river regulation on aquatic invertebrate communities globally. However, there is a scarcity of research in Africa, despite its vulnerability to anthropogenic impacts. This study aimed to compare aquatic invertebrate communities in the Phongolo River, an impacted regulated river, and the Usuthu River, a less impacted unregulated river, in South Africa. It further aimed to ascertain whether Lake Nyamithi, a naturally saline lake receiving water from both of the aforementioned systems, exhibited a stronger similarity to one of the two rivers in terms of its aquatic invertebrate composition. Aquatic invertebrate and water samples were collected from 2012 to 2018 over several surveys. The Usuthu River demonstrated a diverse and sensitive aquatic invertebrate community, emphasising its high conservation value. The Phongolo River demonstrated effects of anthropogenic impact, with taxa more resilient to changes in water quality and flow compared to the Usuthu River. Mismanagement and excessive water use may lead to the loss of any remaining sensitive aquatic invertebrate communities in this river. The presence of invasive molluscan in the Phongolo River and Lake Nyamithi also poses a threat to the native aquatic invertebrate communities. These invasive species are currently absent from the Usuthu River although other invasive species, such as the Australian redclaw crayfish, are found in both river systems. Lake Nyamithi displayed a unique aquatic invertebrate community, distinct from both rivers and their floodplains. This study provides important baseline information on the Usuthu River's aquatic invertebrates and emphasises the need to maintain adequate water flow in rivers and floodplains to protect biodiversity and sensitive species.

Element contamination of the Orange-Vaal River basin, South Africa: a One Health approach.

Numerous low-income groups and rural communities depend on fish as an inexpensive protein source worldwide, especially in developing countries. These communities are constantly exposed to various pollutants when they frequently consume polluted fish. The largest river basin in South Africa is the Orange-Vaal River basin, and several anthropogenic impacts, especially gold mining activities and industrial and urban effluents, affect this basin. The Department of Environment, Forestry and Fisheries in South Africa has approved the much-anticipated National Freshwater (Inland) Wild Capture Fisheries Policy in 2021. The aims of this study were (1) to analyze element concentrations in the widely distributed Clarias gariepinus from six sites from the Orange-Vaal River basin and (2) to determine the carcinogenic and non-carcinogenic human health risks associated with fish consumption. The bioaccumulation of eight potentially toxic elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) was assessed in C. gariepinus from sites with different anthropogenic sources. The human health risks were determined to assess the potential risks posed by consuming contaminated C. gariepinus from these sites. Carcinogenic health risks were associated with fish consumption, where it ranged between 21 and 75 out of 10,000 people having the probability to develop cancer from As exposure. The cancer risk between the sites ranged between 1 and 7 out of 10,000 people to developing cancer from Cr exposure. A high probability of adverse non-carcinogenic health risks is expected if the hazard quotient (HQ) is higher than one. The HQ in C. gariepinus from the six sites ranged between 1.5 and 5.6 for As, while for Hg, it was between 1.8 and 5.1. These results highlight the need for monitoring programs of toxic pollutants in major river systems and impoundments in South Africa, especially with the new fisheries policy, as there are possible human health risks associated with the consumption of contaminated fish.

Effect of an antidepressant on aquatic ecosystems in the presence of microplastics: A mesocosm study.

Emerging pollutants, such as pharmaceuticals and microplastics have become a pressing concern due to their widespread presence and potential impacts on ecological systems. To assess the ecosystem-level effects of these pollutants within a multi-stressor context, we simulated real-world conditions by exposing a near-natural multi-trophic aquatic food web to a gradient of environmentally relevant concentrations of fluoxetine and microplastics in large mesocosms over a period of more than three months. We measured the biomass and abundance of different trophic groups, as well as ecological functions such as nutrient availability and decomposition rate. To explore the mechanisms underlying potential community and ecosystem-level effects, we also performed behavioral assays focusing on locomotion parameters as a response variable in three species: Daphnia magna (zooplankton prey), Chaoborus flavicans larvae (invertebrate pelagic predator of zooplankton) and Asellus aquaticus (benthic macroinvertebrate), using water from the mesocosms. Our mesocosm results demonstrate that presence of microplastics governs the response in phytoplankton biomass, with a weak non-monotonic dose-response relationship due to the interaction between microplastics and fluoxetine. However, exposure to fluoxetine evoked a strong non-monotonic dose-response in zooplankton abundance and microbial decomposition rate of plant material. In the behavioral assays, the locomotion of zooplankton prey D. magna showed a similar non-monotonic response primarily induced by fluoxetine. Its predator C. flavicans, however, showed a significant non-monotonic response governed by both microplastics and fluoxetine. The behavior of the decomposer A. aquaticus significantly decreased at higher fluoxetine concentrations, potentially leading to reduced decomposition rates near the sediment. Our study demonstrates that effects observed upon short-term exposure result in more pronounced ecosystem-level effects following chronic exposure.

PCR amplification and DNA sequence of mcyA gene: the distribution profile of a toxigenic Microcystis aeruginosa in the Hartbeespoort Dam, South Africa.

Using new polymerase chain reaction (PCR) primers, a once known to be under-transcribed microcystin synthetase A (mcyA) gene from the only known toxigenic cyanobacterium Microcystis aeruginosa dominating the Hartbeespoort Dam was consistently amplified from genomic DNA extracted from a set of algal and cell free water samples collected across this dam. In addition to this, five more mcy genes (mcyBCDEG) were also amplified during this study. The resultant mcyA PCR products (518 bp) were purified and sequenced and gave nucleotide sequence segments of 408 bp sizes. The obtained sequence was aligned to the published mcyA gene sequence available online on the NCBI database and resulted in 100% similarity to a 408 bp mcyA gene sequence segment of M. aeruginosa UWOCC RID-1. Furthermore, it was found that the above sequence segment (408 bp) spans from a common base in M. aeruginosa PCC 7806 and M. aeruginosa PCC 7820 from 141 to 548 bp in the N-methyl transferase (NMT) region signifying their closer relatedness to M. aeruginosa UWOCC strains. This study has for the first time amplified mcyA gene consistently from both intracellular and extracellular DNA extracts obtained from algal and cell free water samples, respectively. Sequence data and the amplified mcy genes showed that M. aeruginosa is widely distributed and dominant in this dam.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment.

Organochlorine pesticides (OCPs) are persistent organic pollutants (POPs) widely used in agriculture and industry, causing serious health and ecological consequences upon exposure. This review offers a thorough overview of OCPs analysis emphasizing the necessity of ongoing work to enhance the identification and monitoring of these POPs in environmental and human samples. The benefits and drawbacks of the various OCPs analysis techniques including gas chromatography-mass spectrometry (GC-MS), gas chromatography-electron capture detector (GC-ECD), and liquid chromatography-mass spectrometry (LC-MS) are discussed. Challenges associated with validation and optimization criteria, including accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ), must be met for a method to be regarded as accurate and reliable. Suitable quality control measures, such as method blanks and procedural blanks, are emphasized. The LOD and LOQ are critical quality control measure for efficient quantification of these compounds, and researchers have explored various techniques for their calculation. Matrix interference, solubility, volatility, and partition coefficient influence OCPs occurrences and are discussed in this review. Validation experiments, as stated by European Commission in document SANTE/11813/2017, showed that the acceptance criteria for method validation of OCP analytes include ≤20 % for high precision, and 70-120 % for recovery. This may ultimately be vital for determining the human health risk effects of exposure to OCP and for formulating sensible environmental and public health regulations.