Environmental concentrations, characteristics and risk assessment of microplastics in the Olifants and Breede Catchments, Estuaries and Coastal Areas, Western Cape, South Afric

Esau, Aldean Carmen

Environmental concentrations, characteristics and risk assessment of microplastics in the Olifants and Breede Catchments, Estuaries and Coastal Areas, Western Cape, South Afric

Author(s)

Esau, Aldean Carmen

Cape Peninsula University of Technology

Date Issued

2026

Type

master thesis

Publisher

Cape Peninsula University of Technology

Abstract

Microplastic (< 5 mm) contamination is increasingly being reported from South African aquatic environments but few studies have been done from catchment-to-coast. Thus, the aim of this study was to determine the concentrations, characteristics and risk assessment of microplastics in the Olifants and Breede River catchments, estuaries and coastal areas in the Western Cape, South Africa. Surface water and sediment were collected and analysed for microplastics in the wet and the dry season in relation to disturbances acting on these systems. Microplastics were extracted and identified using microscopy and Fourier-transform infrared spectroscopy (FTIR) analyses. Average microplastic concentrations ranged from 0.24 ± 0.01 particles/L to 0.26 ± 0.02 particles/L in water and 48.30 ± 3.95 particles/kg dry weight to 43.65 ± 2.71 particles/kg dry weight in sediment of the Olifants and Breede systems, respectively. Microplastics were mainly black/grey fibres, 500 – 1000 μm in size and polyethylene terephthalate was the dominant polymer recorded for both systems. Pollution load indices indicated that pollution was present (< 1) across the different regions and seasons of each system for water and sediment. Polymer risk indices in water ranged from low (7.50) to very high (1658.20) and low (4.00) to high (942.20) in the Olifants and Breede systems, respectively, while in sediment, indices ranged from low (6.60) to moderate (47.30) in the Olifants system and low (4.00) to moderate (57.70) in the Breede system. Spatially, in the Olifants system, pollution risk indices in water was categorised as dangerous in the catchment (3190.50), estuary (5748.60) and coast (6943.30) during the wet season, while moderate in sediment along the coast (198.50) during the dry season. In the Breede system, pollution risk indices in water was categorised as dangerous in the catchment (6790.5) during the wet season and along the coast during the wet (2746.40) and the dry season (3136.10), while high in sediment in the estuary (421.80) during the wet season. Seasonally, in the Olifants system, pollution risk indices in water was categorised as dangerous during the wet season (– 63 μm: 11864.3 & 250 μm: 9278.20) and very high during the dry season (63 μm: 1095.20 & 250 μm: 1102.01), while moderate in sediment during the wet (197.30) and the dry (251.30) season. In the Breede system, pollution risk indices in water was categorised as dangerous during the wet season (63 μm: 1223.30 & 250 μm: 9605.10) and the dry season (3273.20), while ranging from high to low in sediment during the wet (703.20) and the dry (104.40) season, respectively. The results from this study serves a baseline for future reaserch and to inform policy makers that govern the protection of these systems so they may be able to develop and implement the necessary mitigation measures to reduce contamination within these systems. The Olifants and Breede systems are ecological important systems. However, the results from the risk assessment indicates that the polymers that accumulate in these system during the wet season pose a threat to the overall health and functioning of these systems from catchment-to-coast. Thus, regular monitoring of these system are crucial.

Additional information

Thesis (Master of Marine Science)--Cape Peninsula University of Technology, 2026

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