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 reduce 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 provide indicators 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 2021
- Kyle Maclean continued his MSc on the amounts of litter intercepted in rivers and storm drains, and took over Emily Spencer’s street litter project. During 2022, he sampled street and river litter in three suburbs of Cape Town: Newlands, Steenberg and Ocean View. His data feed directly into the project modelling the generation of litter across Cape Town. Towards the end of 2022, Kyle elected to upgrade to a PhD, adding chapters on using receipts as tracers of urban litter, and surveying attitudes to litter and littering in the Cape Town communities where he has surveyed street litter loads. He will work on this PhD in collaboration with Prof. Rinie Schenck (UWC) and Prof. Christina Trois (UKZN).
- CB MSc student Shaidan Gonlag modelled the generation of litter across Cape Town, based on the data from Kyle’s project. Thanks to technical advice from Patrick O’Farrell, Shaidan used a suite of GIS tools to generate estimates of litter loads in urban runoff and used his results to identify key sites for installing additional litter interception devices.
- MSc student Chukwudi Nwaigwe joined the plastic team thanks to funding from the MasterCard Foundation. He is studying the amount and composition of litter contributed to beach litter loads by beach goers, using daily accumulation studies at beaches with different numbers of users and comparing litter loads now 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 and Lorien Pichegru spent 5 weeks on the RV Marion Dufresne conducting macro-litter surveys at sea in the southwest Indian Ocean.
- Peter also completed the second year of sampling bottles and lids at beaches to assess the importance of legacy plastic pollution on beach litter surveys. This study was enhanced by opportunistic daily litter sampling at Muizenberg over a period when the beach was bulldozed, releasing large numbers of small legacy pollutants buried in the beach.
- Peter also conducted a baseline survey of beach litter in Namibia, sampling standing stocks of macro- and micro-debris as well as collecting lids and bottles to identify the relative importance of local vs offshore litter sources. Working with La Toya Shivute and her team from the Ministry of Fisheries and Marine Resources, he and Kyle sampled a number of beaches in central Namibia in February 2022. However they were unable to visit the Skeleton Coast due to heavy rains closing the road over the Ugab River, and could not arrange police clearances necessary to access the Sperrgebiet in Tsau Khaeb National Park south of Luderitz. Accordingly, Peter returned to Namibia in July with Coleen Moloney to complete sampling in these areas, with further assistance from La Toya, Diina Mwaala and Jean-Paul Roux. Subsequently, La Toya’s team completed the survey by sampling a few beaches along the coast between Luderitz and Sandwich Harbour. We found very low levels of microplastics, and most macrodebris coming from local sources, consistent with the strong upwelling along the Namibian coast carrying most litter generated offshore away from the coast.
- Kyle and Peter are authoring several chapters on litter sampling and monitoring techniques for the revised African Marine Litter Monitoring Manual in partnership with the Sustainable Seas Trust.
- Vonica Perold returned from an extended leave of absence from her PhD on seabird plastic ingestion after two years on Gough Island. She has taken charge of the newly donated FTIR spectrophotometer, and is assisting other students with identifications of plastic polymers.
- Three papers were published in 2022, and another was accepted for publication.
- To coincide with the 7th International Marine Debris Conference, held in Korea in September 2022, Peter Ryan and Takunda Chitaka wrote a commentary in Environmental Research Letters highlighting the need for effective action to reduce the leakage of plastics into the environment, not more research on their impacts.
- Peter and former MSc student Eleanor Weideman teamed up with Martin Thiel and Daniela Honorato to publish a review on marine plastic pollution in the Western Indian Ocean region in Oceanography and Marine Biology: an Annual Review.
- Peter and Vonica were co-authors on a paper by Anna Robuck reporting global patterns of plastic ingestion by Great Shearwaters, which was published in Frontiers in Marine Science.
- Eleanor, Peter and Vonica led a paper in Marine Pollution Bulletin on the abundance and distribution of microplastics at sea off Tanzania and northern Mozambique in relation to inputs from rivers and urban centres.
- Peter and Lorien observed the impact of the April 2022 KwaZulu-Natal floods on macro-litter at sea off the east coast of South Africa.
- Kyle presented his work on litter interception devices at the African Marine Waste Network conference held in Gqeberha in May.
- Chukwudi joined the Norway-SA Exchange Programme for young researchers working on marine plastics in December.
- The data collected on macro- and microdebris loads on Namibian beaches were used for research projects by two honours students from the University of Namibia, Daniel Fellep and Ndapandula Nakafingo who joined the survey for a few days around Swakopmund in February.
Plastics SA; 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; WIOMSA.
Research team 2022
Prof. Peter Ryan (FIAO, UCT)
A/Prof. Coleen Moloney (Biological Sciences, UCT)
Dr Maëlle Connan (NMU)
Dr Lorien Pichegru (NMU)
Dr Patrick O’Farrell (FIAO, UCT)
Students: Vonica Perold (PhD, UCT); Kyle Maclean (MSc, UCT); Chukwudi Nwaigwe (MSc, UCT); Shaidan Gonlag (CB MSc, UCT).
Research assistant: Melissa Rankin.
Assistants and volunteers: Melissa Rankin and the Dalebrook ‘urchin team’.