Microplastic concentrations on the urban coastline of KwaZulu–Natal, South Africa, and its impact on juvenile fish.

Doctoral Degree. University of KwaZulu-Natal, Durban.The global production of plastics per annum has increased from 1.5 million tonnes in the 1950‘s to 300 million tonnes today. Following this increasing production trend, plastic concentrations have increased over time in marine environments. Improper sewage treatment, industrial spillages, garbage and fishing activities among many others, have made the marine environment a sink for plastic debris. The main aims of this study were to determine (1) microplastic levels within five estuaries along the Durban coastline and on intervening beaches, (2) the incidence of plastic ingestion by estuarine mullet, (3) the effects of plastic ingestion on long–term fish health and (4) the plastic concentrations along the KwaZulu–Natal coastal shelf. To achieve these aims (1) plastic was isolated from estuarine sediment, beach sediment and the surface water of each estuary, (2) fish from the most polluted estuary were dissected to investigate the incidence of plastic ingestion, (3) small juvenile fish were kept in tanks and fed plastics for three months to monitor their growth and survival and (4) coastal water samples were collected using a manta trawl net to quantify floating debris in the ocean. Overall, an attenuating plastic concentration trend away from the city centre was found, with the Durban Harbour, Isipingo and uMgeni Estuaries having the highest contamination levels. The highest recorded plastic levels were found in the Bayhead area of the harbour, with 745.4 ± 129.7 particles per 500 mL, which mostly consisted of plastic fragments. Fibres dominated other estuaries with proportions ranging from 38% of total plastics in the uMgeni Estuary to 66% in the Mdloti. Plastic particle concentration in estuarine sediment generally increased from larger to smaller size classes. High plastic concentrations were also found on the coastal shelf of KwaZulu–Natal, with sites south of the harbour having the highest plastic concentrations, however no seasonal differences were found. There is also evidence pointing toward long range movement of particles and thus pollution at the source must be dealt with before it reaches the open ocean. Seventy three percent of the mullet sampled at the harbour ingested plastic particles with an average of 3.751 ± 4.667 (S.D.) particles per fish. Particles that were ingested were mainly fibres that are thought to come from sewage inputs to the harbour. Juvenile fish in microplastic feeding experiments had lower growth and survival than control fish. This has possible economic and ecological consequences for future fish stocks that use urban estuaries as nursing areas

Impacts of plastic debris on biota and implications for human health: A South African perspective

Entanglement and ingestion of plastics are the main ecological impacts of marine plastic debris on marine biota, but indirect effects such as the transport of alien species and benthic smothering are also important to note. Entanglement of invertebrates, sharks, turtles, birds and marine mammals is mainly caused by macroplastics (>5 mm), and leads to reduced mobility, ineffective foraging and subsequent mortality. The main plastic types associated with entanglement are improperly discarded fishing nets, lines, ropes and straps

Towards characterising microplastic abundance, typology and retention in mangrove-dominated estuaries

Plastic and, particularly, microplastic (MP) pollution is a growing research theme, dedicated largely to marine systems. Occurring at the land–sea interface, estuarine habitats such as mangroves are at risk of plastic pollution. This study compared MP pollution (level, morphotype, polymer composition, size and colour) across four South African estuaries, in relation to the built and natural environment. Mouth status, surrounding human population densities and land-use practices influenced the level and type of MP pollution. Systems that were most at risk were predominantly open estuaries surrounded by high population densities and diverse land use types. Microplastic levels and the diversity of types detected increased with increasing levels of anthropogenic disturbance. Overall, microfibres dominated in estuarine water (69%) and mangrove sediment (51%). Polyethylene (43%) and polypropylene (23%) were the dominant polymers overall. Weathered fishing gear, weathered packaging items and run-off from urban/industrial centres are probable sources of MP pollution

Quantification and characterisation of microplastics ingested by selected juvenile fish species associated with mangroves in KwaZulu- Natal, South Africa

Though the number studies on microplastic ingestion by fish is growing, data on fish species charac- teristic of the South African coastline are scarce. This study quantified and characterised (physically and chemically) microplastics ingested by four species of juvenile fish (viz. Oreochromis mossambicus [Peters, 1852], Terapon jarbua [Forsskål, 1775], Ambassis dussumieri [Cuvier, 1828] and Mugil sp.), within four mangroves along the east coast of South Africa. Microplastics were isolated from whole fish using a proteinase K digestion method, and then quantified and characterised in terms of shape, chemical nature (plastic type), colour and length. Fibres (68%) and fragments (21%) were the dominant shapes found. Of the 174 fish sampled, 52% contained microplastic particles, with 0.79 ± 1.00 particles per fish. The average number of particles per fish did not differ significantly across species within sites and across sites but was higher than in juvenile fish of other species sampled in oceanic habitats. The main plastic types collected using 10 mm filters and identified with Fourier Transform Infrared Spectroscopy (FTIR), were rayon (70.4%), polyester (10.4%), nylon (5.2%) and polyvinylchloride (3.0%). Particle length ranged from 0.1 to 4.8 mm, averaging 0.89 ± 0.77 mm, but irrespective of length, particles were mostly blue in colour. This study provides evidence that juvenile fish inhabiting mangroves are consuming significant quan- tities of microplastics. Importantly, it should be noted that rayon, though the most abundant plastic type found, is a semi-synthetic fibre made from regenerated cellulose that is commonly reported in studies of this nature. The habitats studied serve as nurseries for numerous fish species; however, more detailed studies are needed to assess whether microplastic ingestion could compromise the health of these fish or whether these effects are dependent on species, feeding habit and/or plastic type

Collaboration and infrastructure is needed to develop an African perspective on micro(nano)plastic pollution

Abstract: Our current understanding of environmental micro(nano)plastic (MNP) pollution is driven by field and lab-based studies performed predominantly by and in wealthier countries. However, mismanaged waste and its consequences affect low- and middle-income countries over-proportionately. Evidence suggests that studies on MNP pollution in Africa are critically limited by the scientific infrastructure available, restricting research activities to opportunities for external collaboration with established research laboratories in the Global North. The development of Pan-African research networks and analytical nodes, is required to support intra-African research exchange and training, and drive evidence-based policy relevant to an African context. This can facilitate more inclusive conversations around the harmonization and standardization of methods currently mainly available to the Global North

The number of plastic particles found in estuarine sediment and water samples of five estuaries, Durban, KwaZulu-Natal, South Africa

Widespread disposal of plastics negatively affects biotic and abiotic components of marine systems. Monitoring plastics transitioning through estuaries is vital in assessing terrestrial inputs to oceanic environments. Data on microplastics (particles <= 5mm) in estuaries are scant. This study determined microplastic levels within five estuaries along the Durban coastline and on intervening beaches. Plastics were isolated from estuarine sediment, beach sediment and the surface water of each estuary and characterised. Sediment at the Bayhead area of Durban Harbour was found to contain the highest average plastic concentrations (745.40 ± 129.72 particles per 500ml). Overall an attenuating concentration trend away from the city center was found. Fragments composed the largest percent of plastics (59 %) found in Bayhead, whereas fibers dominated other estuaries (Mdloti - 66 %, uMgeni - 38 %, Isipingo - 45 % and iLovu - 53 %). Plastic particle concentration in estuarine sediment generally increased from larger to smaller size classes. If high input and high retention in the harbour is coupled with high organic and metal pollutant loads, this area can become (if not already) a major environmental hazard