Microplastic abundance, distribution, and diversity in water and sediments along a subtropical river system

Nkosi, Mary; Cuthbert, Ross N.; Shikwambana, Purvance; Dalu, Tatenda

doi:10.1007/s11356-023-28842-w

Cited by 21 publications

(2 citation statements)

References 39 publications

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“…The mean range of water temperature, pH, conductivity and total dissolved solids was 18.3–19.6°C, 7.4–7.9, 256.5–658.5 μS/cm, and 96.6–256.4 mg/L, respectively. The microplastic concentrations ranged from 250 to 2600 particles m −3 (mean: 1058 m −3 ) within the Crocodile River during the cool‐dry season (Nkosi et al., 2023 ).…”

Section: Methodsmentioning

confidence: 99%

“…All identified microplastics were verified using the Nile Red dye (CAS 7385‐67‐3, HYD0718–500 mg, Hycultec, Beutelsbach) as it exploits the hydrophobic properties of microplastic by staining them and illuminating it under a blue fluorescein light, despite its potential to stain biological samples. Once stained, a blue light fluorescein was used to fluoresce and identify the initially suspected microplastics (Nalbone et al., 2021 ; Nkosi et al., 2023 ). Microplastic sizes were quantified based on the stage micrometre and an eyepiece reticle after first initial calibrating and results were presented in micrometres (μm).…”

Section: Methodsmentioning

confidence: 99%

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Field and laboratory microplastics uptake by a freshwater shrimp

Cuthbert,

Nkosi,

Dalu

2024

Ecology and Evolution

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Microplastics are widespread pollutants, but few studies have linked field prevalence in organisms to laboratory uptakes. Aquatic filter feeders may be particularly susceptible to microplastic uptake, with the potential for trophic transfer to higher levels, including humans. Here, we surveyed microplastics from a model freshwater shrimp, common caraidina (Caridina nilotica) inhabiting the Crocodile River in South Africa to better understand microplastic uptake rates per individual. We then use functional response analysis (feeding rate as a function of resource density) to quantify uptake rates by shrimps in the laboratory. We found that microplastics were widespread in C. nilotica, with no significant differences in microplastic abundances among sampled sites under varying land uses, with an average abundance of 6.2 particles per individual. The vast majority of microplastics found was fibres (86.1%). Shrimp microplastic accumulation patterns were slightly higher in the laboratory than the field, where shrimp exhibited a hyperbolic Type II functional response model under varying exposure concentrations. Maximum feeding rates of 20 particles were found over a 6 h feeding period, and uptake evidenced at even the lowest laboratory concentrations (~10 particles per mL). These results highlight that microplastic uptake is widespread in field populations and partly density dependent, with field concentrations corroborating uptake rates recorded in the laboratory. Further research is required to elucidate trophic transfer from these taxa and to understand potential physiological impacts.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Field and laboratory microplastics uptake by a freshwater shrimp

Cuthbert,

Nkosi,

Dalu

2024

Ecology and Evolution

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Abundance and distribution of microplastics in benthic sediments and Cladocera taxa in a subtropical Austral reservoir

Themba,

Dondofema,

Cuthbert

et al. 2024

Integr Envir Assess & Manag

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Pollution of the natural environment by microplastics has become a global issue in ecosystems as it poses a potential long‐term threat to biota. Microplastics can accrue in high abundances in sediments of aquatic ecosystems while also contaminating pelagic filter feeders, which could transfer pollutants up trophic webs. We assess the abundance and distribution of microplastics in benthic sediments and Cladocera taxa in a subtropical Austral reservoir using a combination of geospatial techniques, physicochemical analyses, diversity indices, and multivariate statistics between two seasons (i.e., hot–wet and cool–dry). We found particularly high densities of microplastics during the cool–dry season for both sediments (mean 224.1 vs. 189 particles kg–1 dry weight) and Cladocera taxa (0.3 particles per individual). Cladocera microplastic shapes were dominated by fibers with high densities of the transparent color scheme. Pearson correlation results indicated that sediment microplastic abundances were negatively correlated with chlorophyll–a concentration, temperature, and resistivity, whereas they were positively correlated with pH and salinity during the hot–wet season, with no variables significant in the cool–dry season. Cladocera microplastic abundances were positively correlated with conductivity and salinity during the cool–dry season, but no variables in the hot–wet season. These findings provide insights into the role of reservoirs as microplastic retention sites and the potential for uptake and transfer from lower trophic groups. These insights can be used to strengthen future monitoring and intervention strategies. Integr Environ Assess Manag 2024;1–15. © 2024 SETAC

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Microplastic Concentrations in Sediments and Waters Do Not Decrease in Two Rivers Flowing Through the Kruger National Park, South Africa

Shikwambana,

Foxcroft,

Taylor

et al. 2024

Water Air Soil Pollut

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Plastics are manufactured for various purposes but result in microplastic pollution in aquatic ecosystems. Riverine microplastic occurrence, spatial distribution, and impact have been globally documented but not well understood in Africa. We quantified 36 984 microplastics in riverbed sediment and river water along the Olifants and Sabie rivers, Kruger National Park (KNP), South Africa. These rivers have independent catchments. The microplastic profiles (size, polymer, morphotype, and colour) differed significantly between rivers. Riverbed sediment microplastic (mostly beads) concentrations ranged between 2022 to 9971 n/kg dm, and 2237 to 27 259 n/kg dm, for the Olifants and Sabie rivers respectively. Microplastic (mostly fragments) concentrations in river water ranged between 11 to 50 n/L in the Olifants River, and 4.0 n/L to 41 n/L in the Sabie River. Polyethylene terephthalate (PET) was prevalent in sediment (39%) and water (32%). Concentrations varied along both river stretches but the expected concentration decrease downstream was not observed. This raises transboundary concerns, as all the KNP rivers cross into Mozambique and from there into the Indian Ocean. Given the pervasive plastic pollution already present, there is a need for significant upstream and in-park interventions to reduce the concentration of microplastic in rivers flowing through conservation areas.

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Microplastic abundance, distribution, and diversity in water and sediments along a subtropical river system

Cited by 21 publications

References 39 publications

Field and laboratory microplastics uptake by a freshwater shrimp

Field and laboratory microplastics uptake by a freshwater shrimp

Abundance and distribution of microplastics in benthic sediments and Cladocera taxa in a subtropical Austral reservoir

Microplastic Concentrations in Sediments and Waters Do Not Decrease in Two Rivers Flowing Through the Kruger National Park, South Africa

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