Plastics in the environment

Plastic litter persists for many years, is readily dispersed by water and wind, and has been accumulating in the sea for decades, where it gradually breaks down into ‘microplastics’. It entangles and is eaten by a wide diversity of aquatic fauna, killing them directly, or reducing their appetite. Concerns about microplastics introducing persistent organic pollutants (POPs) into aquatic foodwebs, combined with the discovery of ‘garbage patches’ in all the main ocean gyres, has sparked renewed interest in the subject. This project aims to understand and monitor plastic pollution with a view to reducing the amount entering the environment.

Plastics are used in a plethora of applications because they are lightweight, durable, have excellent barrier properties, and are relatively cheap. These properties also make inappropriately handled waste plastics a serious environmental and economic threat. The most significant threat arises from plastic ingestion, so it is important to understand why organisms ingest plastic. Vonica Perold’s PhD is comparing plastics ingested by seabirds with those found in the environment, and assessing changes in ingested plastic since the 1980s. However, although much remains to be learned about the impacts of plastics on aquatic ecosystems, we know enough to act to reduce waste plastic entering the environment.

Reducing plastic pollution depends on changing human behaviour through education, policy interventions, incentives, etc. Fitz researchers have developed indicators for the levels of environmental plastics, to feedback on whether measures introduced to reduce plastic leakage are effective. We monitor plastic in the environment – through interactions with biota as well as sampling at sea and on beaches. We also infer the origins of ‘general’ marine litter, which could come from a variety of sources, through use of bottles and lids as indicators. Knowing where marine plastic comes from, and how it disperses through the environment, is crucial to target mitigation measures.

A more applied project, funded through the South African Waste Research Development and Innovation Roadmap, is testing the efficacy of litter booms and other passive interception devices to trap litter in rivers and storm drains. This project is also using estimates of urban litter loads to identify key sites for the installation of additional litter traps to reduce the release of land-based litter into the sea

Activities in 2023

• After a two-year break on Gough Island, Vonica Perold made good progress on her PhD on seabird plastic ingestion. She submitted one paper on the use of skua pellets as a way to monitor ingested plastic in South Atlantic seabirds, and has a second paper reporting long-term trends in these species ready to submit.
• CB MSc student Abigail Campbell assessed long-term changes in plastic ingestion among White-chinned Petrels Procellaria aequinoctialis. This is the bird species most often killed on fishing gear off southern Africa, providing a rich data set over the last two decades.
• Kyle Maclean upgraded to a PhD, thanks to an NRF bursary from Prof. Cristina Trois, SARChi Chair for Climate Change and Waste Management at UKZN. Kyle has expanded his original focus from the amounts of litter intercepted in rivers and storm drains to include surveys of the amounts of street litter generated in four areas in Cape Town, across the socio-economic spectrum. He is also assessing attitudes to litter and littering in these four communities in collaboration with Prof. Rinie Schenck, SARChi Chair in Waste and Society at UWC.
• MSc student Chukwudi Nwaigwe completed field sampling for his study of the amount and composition of litter contributed to beach litter loads by beach goers. He used daily accumulation studies at two adjacent beaches with different numbers of users and compared litter loads in 2022/23 with those when beaches were closed during the COVID-19 pandemic. During summer 2022/23 he also repeated Antonio Massot-Mascaro’s 2013/14 MSc study of surf zone litter in False Bay to assess the importance of offshore export of beach litter.
• Peter Ryan used some of his newly-acquired free time to start writing up the backlog of plastics data he has collected over the last few years .

Highlights

• CB MSc student Shaidan Gonlag graduated, and is working on expanding his project to include the latest data from informal settlement street litter for publication.
• PhD student Kyle Maclean celebrated the arrival of his daughter, Lila.
• Five papers were published in 2023, and another was accepted for publication.
• Two papers summarised surveys of plastics at sea. Former MSc student, Eleanor Weideman, led on a paper reporting the distribution and abundance of microplastics off the coasts of Mozambique and Tanzania, and long-time collaborator Giuseppe Suaria led on a paper covering the eastern Atlantic Ocean.
• Peter Ryan published a paper using bottles as litter tracers, showing that illegal dumping from ships is responsible for most drink bottle litter even far from shipping lanes, based on data he collected on the Pitcairn islands in 2019. He also drafted a summary document with Maëlle Connan and collaborators in Australia showing how littering from ships is pervasive throughout the Southern Hemisphere, which was tabled at the UN Plastics Treaty negotiations.
• Peter also completed a paper showing how foreign drink bottle lids indicate a different litter source than foreign drink bottles on South African beaches; while most bottles are made in China, Singapore/Malaysia and the U.A.E., and are dumped illegally from ships, almost all loose lids come from Indonesia, having drifted across the Indian Ocean.
• The revised African Marine Litter Monitoring Manual, featuring several chapters co-authored by team members, was published by the Sustainable Seas Trust .

Key co-supporters
South African Department of Science and Innovation, through the Waste RDI Roadmap, managed by the Council for Scientific and Industrial Research (CSIR); Commonwealth Litter Programme (CLiP); United Nations Environment Programme.

Research team 2023
Emer. Prof. Peter Ryan (FIAO, UCT)
Emer. Prof. Coleen Moloney (Biological Sciences, UCT)
Dr Maëlle Connan (NMU)
Dr Lorien Pichegru (NMU)
Dr Patrick O’Farrell (FIAO, UCT)
Dr Giuseppe Suaria (CNR-ISMAR, Italy)

Students: Vonica Perold (PhD, UCT); Kyle Maclean (PhD, UCT); Chukwudi Nwaigwe (MSc, UCT); Abigail Campbell (CB MSc, UCT).