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.
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 2018
- Eleanor Weideman started an MSc on freshwater plastic pollution, sampling micro-, meso- and macroplastics along the Orange and Vaal Rivers in April and November 2018. She also repeated Gael Arnold’s 1998 sampling of plastic loads in three storm water drains in Cape Town, and monitored the amounts of litter in the Black River system in relation to rainfall events.
- Peter Ryan presented two papers at the 6th International Marine Debris Conference in San Diego in March 2018: one on the results of the Antarctic Circumnavigation Expedition, which integrated the abundance and mass of plastics at sea around Antarctica, and one on the need to measure both the mass and number of plastic items when sampling plastics, noting that macroplastic items account for the vast majority of plastic mass in the environment.
- Peter attended the first meeting of the Scientific Committee for the Ocean (SCOR) working group on floating debris (FLOTSAM), held just before the San Diego meeting.
- Peter also attended a week-long meeting of the UN’s GESAMP Working Group 40 in Bangkok in June 2018. He drafted the section on beach monitoring with Martin Thiel and Alexander Turra, and contributed to other sections of the report on monitoring methods for marine plastics, which was published in early 2019.
- Peter was contracted by the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) to review the impacts of plastics on species covered by AEWA. This led to a global review of plastic entanglement records in birds, based largely on web-based image searches conducted in 17 languages, which was published in Marine Pollution Bulletin.
- Peter also wrote a review article on the plastics waste problem for African Birdlife, and gave several talks on plastic pollution to community groups, and other interested parties.
- Vonica Perold once again ran a project on sampling plastics at sea during the SEAmester at Sea cruise in July 2018, obtaining excellent reviews from the student trainees on the cruise. She also used the opportunity to collect data on meso-and macro-plastic abundance off the east coast of South Africa.
- Monthly clean-ups of intertidal litter at Muizenberg corner run in conjunction with The Beach Cooperative continued throughout 2018, but scoring litter ceased in April, once three years of data had been collected. Only plastics ingested by Sandy Anemones Bunodactis reynaudi were collected throughout 2018; these data will be analysed by honours student Christie Munroe in 2019.
- During a three-month trip to Inaccessible Island from September to December 2018, Peter and Maëlle Connan (NMU) repeated surveys of all beach litter along a 1.1 km stretch of coast between Tern Rock and West Point, an area first surveyed for litter in 1984. Some 7500 litter items were collected weighing an estimated 5 tonnes, including more than 2000 drink bottles. All items small enough to move were placed in one of 10 collection points and subsequently burned with the assistance of Tristan’s Conservation Department staff. A photo-inventory was made of items remaining that were too large to move, or were partly buried and could not be removed. The oldest litter item was made in 1971, but most items were of recent manufacture. Drink bottles were the most abundant class of newly stranded items, with most coming from the orient (mainly China). The marked proliferation in Chinese litter compared to previous surveys (when material from South America predominated), suggests that oriental fishing fleets operating in the South Atlantic are responsible for much of the new beach litter stranding at Tristan.
- Pellets regurgitated by Brown Skuas Catharacta antarctica were collected to assess the types and abundance of plastic in their prey species. Plastic found in pellets containing the remains of only one bird were assumed to have come from that bird. Five seabirds and one land bird (the Inaccessible Rail Atlantisia rogersi) were found to consume plastic. Plastic loads were greatest in Great Shearwaters Ardenna gravis (average of 21 items per adult), White-faced Storm Petrels Pelagodroma marina (4 items per adult) and Broad-billed Prions Pachyptila vittata (3 items per adult; 10 per chick). Compared to previous surveys, plastic loads have increased in Great Shearwaters (doubling compared to 2009 and2011), but not other species breeding at the island. The shearwaters probably show a different trend because in spring they reflect conditions on their wintering grounds in the north Atlantic Ocean.
- Maëlle Connan and Peter Ryan had a project funded through the South African National Antarctic Programme (SANAP) to study diet and plastic ingestion by petrels breeding in the Southern Ocean south of Africa.
- Three papers were published in 2018: two in Marine Pollution Bulletin and one in Environmental Pollution.
- A paper summarising 20 years of meso-plastic sampling around the South African coast showed that most such plastic derives from local sources, which means we have the ability to clean up most of the plastic items that are ingested by birds and turtles in our immediate environment.
Plastics SA, ACE Foundation.
Prof. Peter Ryan (FIAO, UCT)
Assoc. Prof. Coleen Moloney (MaRe, UCT)
Dr Maëlle Connan (NMU)
Aaniyah Omardien (The Beach Collective)
Prof. Hideshige Takada (Tokyo)
Dr Stefano Aliani (CNR-ISMAR)
Guiseppe Suaria (CNR-ISMAR)
Field assistants : Vonica Perold, Christie Munro.