Characteristics and distribution of litter, mesolitter, and microplastics in Table Bay, Cape Town, South Africa

Marine and coastal environments are facing unprecedented challenges due to the presence of litter, mesolitter and microplastics. This study investigated the characteristics and distribution of litter, mesolitter (2-25 mm) and microplastics (MPs; <5 mm) in beach sediment and MPs in seawater samples from Table Bay, Cape Town. Each "litter-category" was assessed and analyzed separately. Samples were collected from two sites: Woodbridge Island and Derdesteen. Litter and mesolitter were sampled along 100 meters of beach for 10 consecutive days during summer and autumn. A total of 11,179 litter items (average: 139.74 ± 20.69 SE items/100 m) and 1,428 mesolitter pieces (average: 4.46 ± 0.60 items/m) were collected, while 688 microplastics (MPs) were extracted from water and sediment samples. Plastic was the most abundant litter and mesolitter recorded. Plastics accounted for 90% by count and 48% by weight in collected litter, with foam (mainly polystyrene) being the most abundant plastic type found. Plastic pellets were the dominant mesolitter type, while fibrous MPs dominated the extracted MPs, which were mainly blue in color. Further analysis of the collected plastic mesolitter using a Spectrum Two Universal Attenuated Total Reflectance Infrared (UATR-IR) spectrometer showed polyethylene (PE: 60%) and polypropylene (PP: 27%) as the dominant polymers in meso-plastics. All the three categories of contaminants (litter, mesolitter and MPs) were higher at Woodbridge Island than Derdesteen, indicating the effects of anthropogenic inputs at the impact site. The anthropogenic inputs at the impacted site stem from beachgoers, residential and commercial inputs, maritime operations, recreational activities, and tide pooling activities at the site. Our study highlighted plastics as a significant component of marine litter, and the prevalence of polyethylene and pellets in mesolitter highlights the urgent need for preventive measures and sustainable clean-ups, to mitigate the short- and long-term impacts of plastics on the marine ecosystems and biodiversity.