Plastics in the ocean
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.
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 marine systems, and how this affects estimates of plastic abundance.
Activities in 2016
- After the five-yearly beach litter survey conducted around the South African coast in 2015, field work for this project was more subdued in 2016. The monthly clean-ups of intertidal litter at Muizenberg corner that are run in conjunction with a volunteer group continued throughout 2016. In addition to generating interesting data on litter types and amounts relative to the adjacent sandy beach, the project has stimulated several community-led initiatives to reduce plastic use in single-use applications such as straws and fast-food packaging.
- Peter Ryan gave several talks on plastic pollution to community groups, and other interested parties. In September he was invited to address officials from the Department of Environment Affairs and visiting experts from the EU on our understanding of plastic pollution in South African marine systems. Peter also is working with the WWF’s Green Trust, which started a programme in November 2016 to limit the environmental impacts of waste plastics.
- In October, Peter was invited to attend a meeting in Barcelona to standardise approaches for estimating the abundance of floating macro debris at sea. Peter was unable to convince the group that his approach (Ryan 2013, Mar. Pollut. Bull.) was the best compromise between statistical rigour and practical feasibility, with the group preferring an even simpler approach which fails to account for changes in detectablity with distance from the vessel. A useful by-product of the trip was a new collaboration with Dr Stefano Aliani, who has been working on floating debris in the Mediterranean for the past decade or so.
- From December 2016 to March 2017, Peter took part in the Antarctic Circumnavigation Expedition (ACE). Shortly before the expedition left Cape Town, he was appointed PI of a project designed to assess the abundance and distribution of microplastics in the Southern Ocean. Stefano Aliani’s PhD student, Giuseppe Suaria, was recruited to sample macro and microplastics on leg 0 of the expedition, as the ship repositioned from Bremerhaven, Germany, to start the ACE cruise in Cape Town, and ended up remaining aboard throughout the entire expedition, providing valuable continuity in sampling protocols. Sediment samples were collected from sandy beaches at six sub-Antarctic and Antarctic islands. Neuston and bongo net samples were collected to sample surface waters for drifting plastic, and zooplankton for ingested plastic, respectively. Very small particles and fibres were sampled by filtering water from the ship’s underway system (4.5 m below sea level) as well as surface samples collected with a bucket from the ship’s bow. Finally, direct observations were conducted to record the abundance and distribution of macro-litter.
- Five papers were published in 2016: two papers arising from Francesca Fazey’s CB MSc project (Environmental Pollution and Marine Pollution Bulletin), one on plastic and other anthropogenic debris in Kelp Gull nests from Minke Witteveen’s MSc (Marine Pollution Bulletin), and two papers on ingestion by albatrosses, fur seals and marine turtles (both in Marine Pollution Bulletin).
- Peter’s review on the ingestion of plastics by marine organisms, invited to appear in Shige Takada’s book Hazardous Chemicals Associated with Plastics in the Environment, was published online in 2016.
- A project on microplastics in the Southern Ocean was funded by the ACE Foundation.
- A new collaboration was formed with Dr Stefano Aliani’s group at CNR-ISMAR (the Italian Research Council’s Institute of Marine Sciences) in La Spezia.
- Peter Ryan spent three months on the Akademik Tryoshnikov collecting data on macro and microplastics in the Southern Ocean during the Antarctic Circumnavigation Expedition.
Plastics SA, ACE Foundation.
Prof. Peter Ryan (FIAO, UCT)
Assoc. Prof. Coleen Moloney (MaRe, UCT)
Prof. Hideshige Takada (Tokyo)
Dr Stefano Aliani (CNR-ISMAR)
Field assistants : Lucy Smythe, Eleanor Weideman