Abstract
Entanglement and ingestion of plastics are the main ecological impacts of marine plastic debris on marine biota, but indirect effects such as the transport of alien species and benthic smothering are also important to note. Entanglement of invertebrates, sharks, turtles, birds and marine mammals is mainly caused by macroplastics (>5 mm), and leads to reduced mobility, ineffective foraging and subsequent mortality. The main plastic types associated with entanglement are improperly discarded fishing nets, lines, ropes and straps. In South Africa and surrounding waters, plastic ingestion has been reported in a number of marine species: sharks (n=10), fish (n=7), turtles (n=1) and birds (n=36). Lethal (macroplastic) and sub-lethal effects (microplastic ≤5 mm) of marine debris on biota have been noted, but at the time of this review there were no published reports on impacts at the population level. Consumed shellfish are possible vectors for the introduction of microplastics into humans. The specific impacts of microplastic ingestion on human health are largely unknown, but additives associated with plastics represent a threat. The research infrastructure in South Africa is insufficient to monitor and characterise marine plastic debris and, in many cases, not in line with global standards. More research effort is needed to understand the impacts of marine plastic debris on humans and marine biota in South Africa, particularly at the population level.
 Significance:
 
 Macroplastics affect marine biota mainly via entanglement and microplastics largely through ingestion.
 Macro- and microplastic interactions with biota can result in sub-lethal effects and mortality but no population effects have been reported for South Africa.
 Consumed shellfish are a potential source of microplastics for humans but their potential effects in humans remain unknown.
 Better infrastructure is needed for improved monitoring and research on the effects of marine debris in South Africa.
Highlights
DATA AVAILABILITY: ☐ Open data set ☐ All data included ☐ On request from author(s) ☐ Not available ☒ Not applicable
While the World Health Organization rates the risk of plastics to humans as low, there is still a need to evaluate the potential effects of microplastics on the South African human population given the country’s reliance on many edible marine species
This need provided the motivation for this review, which assesses the impact of marine plastic debris on biota and the potential implications on human health in South Africa, by drawing on data available for organisms sampled from waters extending from South Africa to more southerly regions, up to the Prince Edward Islands
Summary
Global records of the number of organisms that interact with plastic debris indicate an increase from 265 species in 19971 to 557 in 20152. The widespread bioavailability of microplastics to marine organisms, their potential to act as vectors for both chemicals and microflora, and the resultant impacts on humans and other biota that consume them represent many unknowns, both in South Africa and globally This lack of data has hindered the design and implementation of appropriate mitigation strategies. While the World Health Organization rates the risk of plastics to humans as low, there is still a need to evaluate the potential effects of microplastics on the South African human population given the country’s reliance on many edible marine species This need provided the motivation for this review, which assesses the impact of marine plastic debris on biota and the potential implications on human health in South Africa, by drawing on data available for organisms sampled from waters extending from South Africa to more southerly regions, up to the Prince Edward Islands. This review comments on how South African literature on marine plastic debris (and its impacts) contributes to the global understanding of the phenomenon
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