Plastics in 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 significant environmental threat. Plastic litter persists for many years, is readily dispersed by water and wind, and has been accumulating in the sea for decades. It entangles and is eaten by a wide diversity of marine fauna, killing them directly, or reducing their appetite. Concerns about ‘microplastics’ introducing persistent organic pollutants (POPs) into marine foodwebs, combined with the discovery of ‘garbage patches’ in all the main ocean gyres, has sparked renewed interest in the subject in the last decade or so.
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 significant environmental threat. Plastic litter persists for many years, is readily dispersed by water and wind, and has been accumulating in the sea for decades. It entangles and is eaten by a wide diversity of marine fauna, killing them directly, or reducing their appetite. Concerns about ‘microplastics’ introducing persistent organic pollutants (POPs) into marine foodwebs, combined with the discovery of ‘garbage patches’ in all the main ocean gyres, has sparked renewed interest in the subject in the last decade or so.
Much remains to be learned about the threats that plastics pose to marine ecosystems, but we know enough to act to reduce the amount of waste plastic entering the environment. The most significant impacts of plastics on marine organisms arise from plastic ingestion, so it is important to understand why organisms ingest plastic. Tracking trends in plastic ingestion provides perhaps the best indication of the efficacy of mitigation measures introduced to reduce the amount of plastic in the oceans. However, it is not always feasible to sample plastic ingested by organisms, so we also monitor plastic in the environment, both at sea and washed up on beaches. Much of the recent research in this project has focused on understanding how plastics move through the environment, and how this affects estimates of plastic abundance.
Activities in 2019
- Vonica Perold started a PhD on seabird plastic ingestion, comparing plastics in seabirds over the last three decades with plastics available at sea.
- Eleanor Weideman finished sampling for her MSc on freshwater plastic pollution in the Orange and Vaal Rivers, and estimating macroplastic loads in three Cape Town storm water drains in relation to rainfall events. She will submit her thesis in early 2020.
- Vonica and Eleanor led a well-received project on sampling plastics at sea during the SEAmester at Sea cruise in July. The sampling opportunity added to Vonica’s dataset on meso-and macro-plastic abundance off South Africa.
- In July-August, Vonica and Eleanor went on the winter SCALE cruise, sampling a transect south into the Southern Ocean, and collecting microplastics in newly-formed sea ice. Vonica also sampled plastics during the Gough Island relief voyage (Sep-Oct), and Eleanor led on sampling during the second SCALE cruise (Oct-Nov), when sea ice was again sampled at the end of the winter season.
- Applied Ocean Sciences MSc student Brandon Opie measured daily litter arrival rates at Milnerton and Koeberg beaches in winter, spring and summer, repeating previous studies conducted at these beaches by former MSc students in 1994/95 and 2012. Winter litter arrival rates have increased compared to the 1990s, but summer rates have decreased considerably at Milnerton, probably due to the deployment of a litter boom and other efforts to stem the flow of litter down the Black River.
- BSc Hons student Christie Munroe assessed selectivity among litter ingested by Sandy Anemones Bunodactis reynaudi in the intertidal at Muizenberg, based on monthly clean-ups run in conjunction with The Beach Co-op. She also conducted field experiments to determine the factors driving plastic ingestion in this species.
- BSc Hons student Elena Piller conducted a series of experiments to estimate sedimentation rates of buoyant plastic items across a salinity gradient. This project built on former CB MSc student Francesca Fazey’s experiment, conducted solely in sea water, and found a strong seasonal signal in sedimentation rates as well as generally lower biofouling in freshwater systems.
- NOAA-funded PhD student Anna Robuck visited from the University of Rhode Island to sample plastics from Great Shearwaters Ardenna gravis, working with Vonica Perold.
- The first survey of seafloor litter off South Africa was published in a collaboration with Tracy Fairweather and Deon Durholtz, based on rubbish caught during the 2019 hake stock assessment survey.
- Peter Ryan chaired the WIOMSA Group of Experts on Marine Plastics and hosted the inaugural meeting of the group in Cape Town.
- Peter attended the second meeting of the Scientific Committee for the Ocean (SCOR) working group on floating debris (FLOTSAM), held in Utrecht, Netherlands, via Skype. This workshop resulted in a review paper on the physical and biological processes driving the transport of plastics in marine systems which is in press with Environmental Research Letters.
- Peter was invited to teach on UNEP’s first “Train the Trainers” workshop designed to kick-start plastics monitoring programmes. Held in Mombasa, Kenya, in August, it was attended by country representatives from throughout the western Indian Ocean region. After the workshop, Peter sampled bottles and mesoplastics along the south-central Kenya coast.
- Peter also visited the Pitcairn Islands in Oct-Nov 2019 to assess the severity of the plastics ‘problem’ at these very remote islands. Henderson Island, the largest of the Pitcairn Islands, has been reported to be one of the most polluted islands in the world, yet the density of plastic at sea and on other islands in the group is modest, suggesting that Henderson Island is anomalous in accumulating high densities of floating litter.
- A paper on bottles washing ashore on Inaccessible Island, which identified Asian shipping as a major source of litter in the central South Atlantic Ocean, was published in the Proceedings of the National Academy of Sciences of the USA.
- A further four papers were published in 2019: two in Marine Pollution Bulletin, one in Environmental Pollution and one in Elementa: Science of the Anthropocene. Peter Ryan also was a co-author on the UN GESAMP report on monitoring marine plastics.
- Peter was contracted by the CSIR to write two of a suite of five review papers on marine plastics in South Africa planned for publication in the South African Journal of Science in 2020.
- Three papers arising from the ACE cruise were finalised, with two published in early 2020.
Plastics SA, ACE Foundation; Swiss Polar Institute, South African Department of Science and Technology, 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 2019
Prof. Peter Ryan (FIAO, UCT)
A/Prof. Coleen Moloney (Biological Sciences, UCT)
Dr Maelle Connan (NMU)
Aaniyah Omardien (The Beach Collective)
Dr Stefano Aliani (CNR-ISMAR)
Guiseppe Suaria (CNR-ISMAR)
Students: Vonica Perold (PhD, UCT); Eleanor Weideman (MSc, UCT); Brandon Opie (AOS MSc, UCT); Christie Munroe (Hons, UCT); Elena Piller (Hons, UCT).