Sea-surface microplastic concentrations along the coastal shelf of KwaZulu-Natal, South Africa.

Ocean pollution is a global issue; yet limited quantitative data on microplastic concentrations are available for the South African coastal shelf. Estuarine outlets within industrial areas that are found along the coastline serve as conduits for plastics and other pollutants to the ocean. This study investigated coastal plastic concentrations around KwaZulu-Natal. Forty-three manta trawl samples were collected and analysed over a period of one year. An average of 4.01 ± 3.28 plastic particles/100 m was found in surface trawls. Plastic concentrations in winter were significantly higher than those in summer (5.54 ± 3.26 and 2.96 ± 2.94 particles/100 m respectively). The highest concentrations of plastics were found south of the city of Durban, with the highest concentration at Isipingo winter with 12.2 particles/100 m. Among the summer samples, the highest concentration of particles was off Amanzimtoti (9.54 particles/100 m). The main plastic forms were fragments, films and fibres that were commonly white, clear, opaque, blue and black in colour. High plastic concentrations in the Durban area and sites close-by were expected due to the high levels of urbanization in the area, however, the difference in concentrations found between winter and summer was not expected and may have been due to the prevailing wind and/or current conditions on the sampling date.