Microplastic concentrations and risk assessment in water, sediment and invertebrates from Simon's Town, South Africa.

Plastic pollution is an ever-increasing threat globally and poor waste management in South Africa has caused an increase in plastic leakage into the environment. Plastic waste in the environment are categorized according to size and plastic particles smaller than 5 mm in size are regarded as microplastics (MPs), and little to no research has been done on MPs pollution within the marine coastal environment and rocky shores in South Africa. Sampling was done in February 2020 at a rocky shore within Simon's Town Marina, Cape Town. MPs were extracted from collected water (n = 5), sediment (n = 5) and biota (n ≤ 30) samples. The extracted MPs were further classified based on shape, colour, size and an attenuated total reflectance Fourier-transform infrared (ATR-FTIR) instrument was utilized for polymer type identification The risks posed by MPs because of concentration at which they occurred and chemical composition were assessed in all the sample types. As expected, MPs were higher in sediment (38 ± 2 MP/kg) than in water (0.37 ± 0.06 MP/L) as the area has low water energy, allowing MP particles to settle within the sediment. Filter-feeding organisms had the lowest average MP particle concentrations (0.28 ± 0.04 MP/g) but displayed the highest variation of MP particle colours due to the non-selective feeding strategy, where other feeding strategies ingested mostly black/grey particles. The dominant MP size was between 100 µm and 500 µm in size for all samples combined, with the most abundant MP polymer type being nylon (27.27 %), polyethylene terephthalate (PET) (18.18 %) and natural MP particles such as cotton (18.18 %). The risk assessment indicated that polymer type poses a greater risk of MP pollution than MP concentrations.

Stormwater outlets: A source of microplastics in coastal zones of Cape Town, South Africa.

The runoff from stormwater outlets are potential sources of microplastics (MPs) in coastal zones. The characteristics and concentrations of MPs in coastal water, sediment and biota (mussels, whelks and sea urchins) were measured in summer (2020/2021) (dry season) and winter (2021) (wet season) from three sites (Camps Bay, Mouille Point and Three Anchor Bay) in Cape Town. MPs were characterised visually using a stereo microscope and chemically using spectroscopy. MP concentrations were higher in water and sediment during winter, and higher in biota in summer. Compared to control sites, MPs were higher at all impact sites sampled. MPs extracted were mainly black polyester (PEST) fibres, 1000 to 2000 µm in length averaging 0.15 MPs/L in water, 52.11 MPs/kg dry weight in sediment and 1.35 MPs/g soft tissue wet weight in biota. The results indicate that coastal stormwater systems are potential sources of MPs in the coastal environment of Cape Town.

Microplastic pollution and risk assessment in surface water and sediments of the Zandvlei Catchment and estuary, Cape Town, South Africa.

Microplastic (MP) (plastic <5 mm) pollution in South Africa is widespread but few studies have been done in catchments and estuaries of the country. The aim of this study was to investigate the abundance, characteristics and risks posed by microplastics in the Zandvlei Catchment and Estuary in Cape Town, South Africa. Water and sediment were sampled between 2019 and 2021, during wet and dry seasons, MPs extracted and identified using microscopy and fourier-transformed infrared spectrophotometry (FTIR) analyses. MP abundances were 70.23 ± 7.36 (standard error) MPs/Kg dw in sediment and 2.62 ± 0.41 MP/L in water samples for the study period. Lower reaches of the catchment and upper reaches of the estuary can be considered sinks for MP contamination as these sites recorded higher MP abundances. MPs were mainly transparent fibres smaller than 0.5 mm. Polyethylene (46%) followed by polypropylene (16%) fibres were the most common polymers recorded. Pollution load indices in MPs were categorised as dangerous in both water and sediment. MP polymer risk indices ranged from moderate in catchment sediment to very high in catchment water. Pollution risk indices were categories as dangerous in water (catchment and sediment) and sediment estuary but low in catchment sediment. Ecological risk assessments hence indicated that polymers in water and sediment were mostly dangerous and poses a threat to the ecological health of both the catchment and estuary studied.

Environmental concentrations, characteristics and risk assessment of microplastics in water and sediment along the Western Cape coastline, South Africa.

Plastic debris is accumulating in all environments globally and South Africa's poor waste management plan has led to an increase in plastic contamination throughout the country. Information about microplastics (MPs) in urban and rural coastal environments in South Africa is poor. The aim of this study was to determine coastal MP concentrations in water (particles/L) and sediment (particles/kg). Sampling took place in summer of 2020 during low tide at 14 sites, along the coast of the Western Cape, South Africa. MPs were extracted and analysed based on shape, color, size and polymer type (using an ATR-FTIR). An ecological risk assessment was done to assess the potential risks posed by MPs in all sample types. Sediment MP concentrations (185.07 ± 15.25 standard error particles/kg) were higher than water (1.33 ± 0.15 particles/L). Gordon's Bay (site 12) had the highest MP concentrations in sediment samples (360 ± 36.74 particles/kg), identifying harbors as the main source for MP contamination. Kalk Bay (site 9) displayed the highest concentration in water samples (4.97 ± 0.18 particles/L), suggesting that the source of MPs are from stormwater outfall pipes and human activities. Filaments were the most dominant MP shape (89%) for all samples, with black/grey (water) and transparent (sediment) being the most dominant colors (31% and 31% respectively). Dominant sizes were 1000-2000 µm in water and 2000-5000 µm in sediment. Polyethylene terephthalate (PET) (29%) was the most dominant polymer type recorded in water samples and natural fibres (mainly cotton) (32%) recorded in sediment. Based on the risk assessment, MPs recorded at Mouille Point (site 6) poses the greatest ecological risk associated with polymers. MP concentrations reported in this study provide a baseline for future studies along the Western Cape coastline of South Africa.

Characteristics and Risk Assessment of Microplastics in Water and Mussels Sampled from Cape Town Harbour and Two Oceans Aquarium, South Africa.

The aim of this study was to measure the characteristics and risk assessment of microplastics (MPs) in Cape Town Harbour (CTH) and the Two Oceans Aquarium (TOA) in Cape Town, South Africa from 2018 to 2020. Water and mussel MP samples were analyzed at 3 sites in CTH and TOA, respectively. Microplastics were mainly filamentous, black/grey and 1000-2000 µm in size. A total of 1778 MPs, averaging 7.50 (± 0.6 standard error of the mean, SEM) MPs/unit were recorded. Average MP concentrations were 10.3 ± 1.1 MPs/L in water and 6.27 ± 0.59 MPs/individual or, based on weight, 3.05 ± 1.09 MPs/g soft tissue wet weight in mussels. Average MPs in seawater in CTH (12.08 ± 1.3 SEM MPs/L) was significantly higher (4.61 ± 1.1 MPs/L) than inside the TOA (U = 536, p = 0.04). Various risk assessment calculations indicate that MPs in seawater poses a greater ecological risk than MPs in mussels at the sites sampled.

Concentrations and risk assessment of metals and microplastics from antifouling paint particles in the coastal sediment of a marina in Simon's Town, South Africa.

Maintenance of maritime vessels includes the removal of paint from hulls that are sources of metals, antifouling paint particles (APPs) and microplastics (MPs) that end up in the coastal environment. Simon's Town is a small urban town in False Bay, Cape Town, South Africa, where maritime activities take place (there is a naval harbour, marina and shipyard). The aim of this study was to measure metals, APPs and MPs in Simon's Town, to assess the impact of maritime activities and a storm water pipe in a sheltered marina. Sediment samples were collected from six sites during winter 2018. Sediment and extracted APPs were analysed for metal concentrations (Al, As, B, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sb, Sn, Sr, V and Zn) and MPs characterised based on type (shape and polymer), colour and size. Highest average metal concentrations in sediment for all sites were Fe (32228 ± SEM 4024), Al (12271 ± 1062) and Cu (1129 ± 407). Metals in paint particles were highest for Fe (80873 ± 19341), Cu (66762 ± 13082) and Zn (44910 ± 1400 µg/g). Metal and MP fragment concentrations were highest at the slipway of the shipyard, decreasing with increased distance from the slipway. MP filaments were highest close to the storm water outfall pipe. Our results suggest that shipyards are potential sources of metals and MP fragments (mainly APPs), with storm water pipes potential sources of MP filaments. Various indices applied to assess the potential impacts of metals and MPs suggest that these contaminants have the potential to adversely impact the intertidal ecosystem investigated.

Investigation into the bacterial diversity of sediment samples obtained from Berg River, Western Cape, South Africa.

This study used conventional culturing and 16S rRNA metagenomics analyses to assess the diversity of bacterial communities in sediment samples obtained from the Berg River, Western Cape, South Africa. Samples were collected from six points: a residential and recreational area, an industrial area, an informal residential settlement, a point next to a wastewater treatment plant (WWTP), a pumping station, and a residential and agricultural farming area along the river. High bacterial counts recorded on general selective and differential culture media signify substantial microbial contamination along the sampling sites. The most prevalent bacterial phyla detected (through metagenomics analyses) along the sampling sites were Proteobacteria (61%), Planctomycetes (9.5%), Firmicutes (7.8%), Bacteroidetes (5%), Acidobacteria (4.6%), and Actinobacteria (4.6%). Some members of the identified predominant bacterial phyla, genera, and classes are important public health bacteria that have been implicated in human diseases and outbreaks, while some others are metal or hydrocarbon tolerant, indicating possible significant environmental pollution. Notable human pathogenic genera such as Bacillus, Clostridium, Shigella, Legionella, Mycobacterium, and Pseudomonas were identified in varying percentages at five of the six sampling areas. Fecal contamination was particularly rife at all residential areas, with the informal housing area being the most notably polluted. Diverse functional pathways were predicted for identified bacteria, such as those associated with different chronic and infectious human diseases as well as those related to hydrocarbon and metal remediation. The point next to a WWTP contained vastly diverse groups of bacterial contaminants as well as the most abundant pathway identities and titles.

Abundance and characteristics of microplastics in retail mussels from Cape Town, South Africa.

With the increased occurrence of plastics in the marine environment, ingestion of microplastics (MPs) by marine invertebrates such as mussels is increasing globally. This study investigated the occurrence of microplastics in mussels sold at supermarkets and wholesalers in Cape Town, South Africa. Soft tissue was extracted from mussels, digested and identified by microscopy and FTIR-ATR. MP filaments (70%) and fragments (30%) were the only types of MPs identified and an average of 0.04 MPs/g soft tissue and 3.8 MPs/mussel recorded. Blue/green (44%) and black/grey (40%), smaller than 2000 µm were the most prominent MPs recorded and the main polymer type was filamentous polyethylene terephthalate (PET). Our results suggest that retail mussels in Cape Town do not contain as high concentrations of MPs when compared to other investigations and routine monitoring of seafood in the country is suggested.

Occurrence and probabilistic risk assessment of PAHs in water and sediment samples of the Diep River, South Africa.

This study investigated the levels of polycyclic aromatic hydrocarbons (PAHs) in water and sediment samples of the Diep River freshwater system of Western Cape Province, South Africa. A solid-phase extraction - gas chromatography - flame ionisation detection (SPE-GC-FID) method was utilised to simultaneously determine the 16 United States Environmental Protection Agency (US EPA) listed priority PAHs in water and sediment samples. The seasonal averages of individual PAH detected at the studied sites, ranged between not detected (Nd) and 72.38 ± 9.58 µg/L in water samples and between Nd and 16.65 ± 2.63 µg/g in the corresponding sediment samples. The levels of PAHs measured in water and sediment samples were subjected to probabilistic risk assessment to predict the possibility of regulatory values being exceeded. The average percentage exceedence of 63.26 was obtained for PAHs in water samples of the Diep River, while the corresponding average percentage exceedence obtained for sediment sample was 63.71. Sufficient exposure of humans and aquatic organisms to the exceedance levels obtained, would cause adverse health effect.