Microplastics are small plastic fragments that have been found around the world, however, research into microplastics in Africa and freshwater systems remains insufficient. In this study, the ...snapshot microplastic profile of an urban stream was assessed in the Braamfontein Spruit, located in Johannesburg the largest city in South Africa. The abundance of microplastics was determined in water, Chironomus sp. larvae and sediment, while in situ parameters were taken to investigate their relationship to the microplastic profile of the different matrices. Microplastics were detected in water (mean of 705 particles mˉ3), Chironomus sp. larvae (mean of 53.4 particles gˉ1 wet weight) and sediment (mean of 166.8 particles kgˉ1 dry weight). The study found evidence of how urban stream characteristics such as a weir, stream depth and velocity could affect the abundance and dispersion of microplastics. The results indicate that areas of increased depth and decreased flow allowed microplastics to settle down to the sediment where benthic macroinvertebrates could ingest these fragments. Large obstructions like a weir also increased microplastic counts in sediment and invertebrates above the obstruction, with a decrease of fragments after the obstruction, however, microplastics in surface water were able to flow over the obstruction and increase in abundance downstream. This study concludes that first order urban streams such as the Braamfontein Spruit may be contributing large numbers of microplastics to higher order streams and large rivers in times of increased flow.
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•Microplastics had a 100% prevalence in Chironomid larvae groups.•Stream characteristics could influence microplastic distribution.•Microplastic abundances varied depending on what matrix was being analysed.•A weir decreased microplastic loads downstream in sediment and invertebrates.
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.
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.
