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. The main role for Fitz researchers is to 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.
Activities in 2020
- Vonica Perold started a PhD on seabird plastic ingestion, comparing plastics in seabirds over the last three decades with plastics available at sea. She published a paper in Marine Pollution Bulletin on decadal changes in plastic litter regurgitated by albatrosses and giant petrels at Marion Island, and also co-authored a paper in the Journal of Hazardous Materials showing the presence of multidrug resistant bacteria on plastic litter in Zanzibar. She took a one-year leave of absence to assist the RSPB as a field assistant on Gough Island from Sept 2020.
- Eleanor Weideman graduated with her MSc on freshwater plastic pollution, and published two papers from her thesis in Science of the Total Environment: one on pollution in the Orange and Vaal Rivers, and one on macroplastic loads in three Cape Town storm water drains. She also wrote up two further papers, one in Marine Pollution Bulletin reporting three years of monthly sampling of intertidal litter on the rocky shore at Muizenberg conducted in collaboration with The Beach Co-op, and one in Environmental Pollution based on Christie Munroe’s Hons project on plastic ingestion by the Sandy Anemone Bunodactis reynaudi.
- Brandon Opie completed his research project for an MSc in Applied Ocean Sciences based on daily litter arrival rates at Milnerton and Koeberg beaches in winter, spring and summer. Autumn sampling at Milnerton was conducted in April 2020, during the COVID-19 lockdown, led by Eleanor Weideman. Winter litter arrival rates have increased compared to the 1990s, but summer rates have decreased considerably at Milnerton, probably due to efforts to reduce litter loads in the Black River.
- Two BSc Hons students completed field-based plastic projects despite the COVID-19 pandemic. Kyle Maclean continued the ‘litter trace’ experimental release of marked plastic and wood blocks at river mouths to estimate the proportion of land-based litter that washes ashore shortly after entering the sea. Emily Spencer was prevented from processing microplastic samples collected by Vonica Perold and Eleanor Weideman during Antarctic cruises in 2019 by lack of access to UCT labs. Instead she explored the use of plastic and other litter as sunshades by Cape Urchins Parechinus angulosus. Sampling for this project continues every spring low tide at the key study site, near Kalk Bay, where urchins use plastic much more than all other sites sampled around the Cape Peninsula.
- At the start of 2020, Maëlle Connan and Ben Dilley conducted 2.5-months fieldwork at Kerguelen thanks to a collaboration with French colleagues Christophe Barbraud and Yves Cherel. They assessed plastic loads in small burrowing petrels by sampling Brown Skua Stercorarius antarcticus regurgitations.
- The City of Cape Town’s Gregg Oelofse provided the opportunity to sample beach litter during the initial COVID-19 lockdown in April-May 2020. This prompted two papers, one on the impacts of COVID lockdowns on street litter published in Environmental Processes, and one showing the limited dispersal of litter from rivers entering into False Bay that is in press with Estuarine, Coastal and Shelf Science.
- Peter Ryan led on a paper that sampled superficial and buried plastic pollution across a wide range of spatial scales on a remote beach in the West Coast National Park, which was published in Frontiers in Marine Science. This showed that although microplastics dominate in terms of the numbers of plastic items, surface macrolitter accounts for more than 90% of the mass of plastic. This highlights the value of cleaning macrolitter before it degrades into microplastics.
- Peter also published six other papers: two review papers among a suite of five regional reviews in the South African Journal of Science; one describing seafloor litter off South Africa based on rubbish caught during hake stock survey trawls in Marine Pollution Bulletin; one showing the diverse origin of bottles on Kenyan beaches in Waste Management; and two papers in Marine Pollution Bulletin arising from his visit to the Pitcairn Islands in 2019.
- An impressive 21 papers were published in 2020.
- Peter Ryan was awarded a two-year contract from 2021 to produce an inventory of litter interception devices currently deployed on South African rivers. 2020 Hons student, Kyle Maclean, will undertake this study, which includes assessments of the amounts of litter intercepted and the efficacy of different designs used to trap litter. HRA Patrick O’Farrell will help to supervise a CB MSc project using GIS to identify the most important sites in South Africa for installing additional interception devices.
- Peter Ryan and Eleanor Weideman teamed up with Martin Thiel and Daniela Honorato from Chile to successfully tender to conduct a review of marine plastic pollution in the Western Indian Ocean region.
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 2020
Prof. Peter Ryan (FIAO, UCT)
A/Prof. Coleen Moloney (Biological Sciences, UCT)
Dr Maelle Connan (NMU)
Dr Patrick O’Farrell (FIAO, UCT)
Aaniyah Omardien (The Beach Co-op)
Dr Stefano Aliani (CNR-ISMAR)
Guiseppe Suaria (CNR-ISMAR)
Students: Vonica Perold (PhD, UCT); Eleanor Weideman (MSc, UCT); Brandon Opie (AOS MSc, UCT); Kyle Maclean (Hons, UCT); Emily Spencer (Hons, UCT).
Assistants and volunteers: Nicola Okes, Melissa Rankin.