An extreme storm that struck Durban, on the east coast of South Africa, on 10 October 2017 resulted in the loss of two ship containers, packed with 2.25 billion nurdles polyethelene, into the harbour waters and then into the Indian Ocean. While the event was locally regarded as an environmental disaster, observations of nurdles that washed up on South Africa’s east coast and beyond have provided an opportunistic scientific platform to observe their dispersion both locally and sub-globally.

Locally, the nurdles initially dispersed northward, under the influence of south-westerly winds and nearshore northward. Those that weren’t deposited on the beaches were circulated offshore into the Agulhas Current where they were rapidly transported south-westwards along the east coast of South Africa as far as the South-Western Cape, some 1 300 km away.

Ocean circulation patterns, supported by NOAA drifter tracks, indicate that the nurdles could circulate via the Indian Ocean gyre eastwards towards Western Australia (WA), while others may leak westward into the South Atlantic Ocean to Brazil. High concentrations of nurdles fitting the same description as those from the spill were observed on St Helena Island (South Atlantic Ocean) during May 2018, within a similar timeframe as NOAA drifter tracks. Low concentrations of nurdles with the same signature as those from the Durban spill have also been observed at a beach near Walpole, WA since November 2018. Satellite-tracked drifters suggest transport times of approximately 500 days to Australia and Brazil, however the transport times of the nurdles on the ocean surface may be slightly faster than the drifters, which are centered at a depth of 15 m.

Approximately one-third of the nurdles have been recovered from the South African beaches. Whilst they may now be widely dispersed, the ocean currents will remain as a conduit for their onward sub-global circulation.