Entanglement of animals is one of the main environmental impacts of waste plastic. A 2015 review of entanglement records found that the proportion of affected seabirds increased from 16% of species ...to 25% over the last two decades. However, this was restricted to published records; Google Images and other web-based sources indicate that at least 147 seabird species (36%), as well as 69 freshwater birds (10%) and 49 landbirds (0.5%) from 53 families have been entangled in plastic or other synthetic materials. Fishing gear is responsible for entangling most species (83%), although it is often difficult to differentiate entanglement from bycatch on active gear. Mitigation measures include banning high-risk applications where there are alternatives (e.g. six-pack rings), discouraging the use of high-risk items (e.g. balloons on strings, ‘manja’ kites), and encouraging fishers to not discard waste fishing gear by providing specific receptacles and associated educational signage in fishing areas.
•55% of bird orders and 21% of bird families are recorded to be entangled in plastic.•36% of seabird species are now known to be entangled in plastic litter.•Freshwater birds (10% of species) have less risk of entanglement than seabirds.•Fishing gear entangles 83% of the 265 entangled bird species globally.•The fairly small set of problem items allows for targeted mitigation measures.
Floating persistent debris, primarily made from plastic, disperses long distances from source areas and accumulates in oceanic gyres. However, biofouling can increase the density of debris items to ...the point where they sink. Buoyancy is related to item volume, whereas fouling is related to surface area, so small items (which have high surface area to volume ratios) should start to sink sooner than large items. Empirical observations off South Africa support this prediction: moving offshore from coastal source areas there is an increase in the size of floating debris, an increase in the proportion of highly buoyant items (e.g. sealed bottles, floats and foamed plastics), and a decrease in the proportion of thin items such as plastic bags and flexible packaging which have high surface area to volume ratios. Size-specific sedimentation rates may be one reason for the apparent paucity of small plastic items floating in the world's oceans.
Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere ...and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world's oceans from 24 expeditions (2007-2013) across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N = 680) and visual survey transects of large plastic debris (N = 891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic <4.75 mm and meso- and macroplastic >4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove <4.75 mm plastic particles from the ocean surface.
Display omitted
•Foreign bottles are much more abundant on remote than urban beaches in Kenya.•The urban-remote gradient suggests that local bottles seldom disperse very far.•Most foreign HDPE and ...glass bottles drift across the Indian Ocean from Asia.•Most foreign PP bottles come from island nations in the western Indian Ocean.•Most Chinese PET bottles are dumped illegally from ships.
Identifying the source of marine litter is essential to design effective mitigation measures to reduce plastic leakage into marine ecosystems. Kenya recently banned the use of polyethylene bags, but PET drink bottles remain a contentious source of litter in the country. I collected bottles and other single-use containers at nine Kenyan beaches, and compared their composition, country of manufacture and approximate age (time since manufacture) to bottles collected in coastal towns. Locally manufactured bottles dominated street litter (98%) and on urban beaches (93%) but became increasingly uncommon with distance from coastal towns, comprising only 30% of bottles at remote beaches. These steep spatial gradients indicate that most local bottles do not disperse far from source areas. The presence of lids is important for long-distance dispersal of glass and PET bottles, and many PET bottles littered in urban areas lack lids. HDPE bottles are much more common on beaches than on streets, and most come from Indonesia. The presence of epibionts and bite marks suggest that most HDPE bottles have drifted in the South Equatorial Current from southeast Asia, whereas foreign PP bottles mostly come from Indian Ocean island states. Reducing plastic leakage in southeast Asia should reduce the amount of beach litter throughout the western Indian Ocean. Some foreign PET bottles come from neighbouring states, but many are probably dumped illegally from ships operating from Asia. In addition to reducing plastic leakage from land-based sources, we need to ensure compliance with MARPOL Annex V regulations banning the disposal of plastic wastes at sea.
South Africa is thought to be one of the worst contributors of plastic into the sea globally. Although some plastic items derive from offshore sources (mainly fishing and other maritime activities, ...but also long-distance transport), the importance of local, land-based sources is indicated by the composition of beach debris and the concentration of macro-, meso- and microplastics close to urban source areas. Some 60–90% of plastic from land-based sources is expected to strand on beaches, but plastic standing stocks on beaches are much lower than global model predictions of land-based pollution. Burial in beaches and transport into backshore vegetation are significant sinks, although this plastic is likely to be released as the climate crisis leads to rising sea levels and more extreme storms. Most buried items are fairly small, while many larger items, which account for most of the mass of plastic, are removed from beaches by cleaning efforts. However, even daily accumulation rate estimates – which exclude the effects of cleaning – fall well short of model predictions of plastic leakage from land-based sources. Oceanographic models predict that plastics entering the sea from South Africa are exported to the South Atlantic and Indian Oceans, with the proportion depending on source location and item density. At sea, floating macroplastic is concentrated close to urban centres. Farther offshore, plastic items tend to be large and buoyant because biofouling causes small, low buoyancy items to sink. Size-selective removal of plastics by biota might also contribute to the paucity of floating microplastics (25 mm). • The seabed is a long-term sink for marine plastics, but densities of plastic on the seabed around South Africa are still modest. • The global model prediction of plastic leakage from South Africa into the sea probably is a gross overestimate.
Despite a large literature on the impacts of micro-plastic pollution in marine ecosystems, very little research has focused on these pollutants in freshwater ecosystems. Recently, however, a few ...studies have demonstrated that micro-plastic pollutants are ingested by freshwater taxa, including birds. To explore this potential environmental threat in African freshwater systems we quantified micro-plastic pollutants in the faeces and feather brushings of seven southern African duck species. We analysed 283 faecal samples and 408 feather brushings, and found that 5% of faecal samples and 10% of feather samples contained micro-plastic fibres. The presence and abundance of micro-fibres differed between sampling sites, with significantly higher amounts recorded for the site that received effluent from a sewage treatment facility. Additionally, micro-fibre presence differed across duck species, indicating that foraging behaviour affects plastic ingestion. Our study confirms that African freshwater ecosystems and the biodiversity they support are under threat from micro-plastic contamination.
•Micro-plastics are ingested by African ducks in two freshwater systems.•Foraging method affects the amount of micro-plastic in duck faeces.•Ducks also carry micro-fibres on their feathers.•Plastic loads are greater at a site receiving water from a sewage treatment plant.
Recent studies using bottles as tracers have shown that illegal dumping from ships is responsible for the rapid increase in drink bottles washing up on oceanic islands and at remote continental ...beaches away from local litter inputs. However, these studies have been in areas with moderate to high levels of shipping activity. I examined bottles stranded on the Pitcairn Islands in the central South Pacific, which are far from major shipping routes. Drink bottles from Asia dominated, with most coming from China. The top four brands (three Chinese and one multinational) were the same as at Tristan da Cunha in the central South Atlantic Ocean, which lies on the shipping route between South America and Asia. Bottle ages also were similar at Pitcairn and Tristan, indicating that vessels are the main source of bottles at both islands. Stricter controls are needed to reduce illegal dumping of plastics at sea.
•Ship-based surveys detect evidence of the South Atlantic ‘garbage patch’.•Litter density from 3 to 8°E was 2.5 times greater than in waters closer to Africa.•Most litter was plastic and carried ...epibionts so had been adrift for a long time.
A distance-based technique was used to assess the distribution and abundance of floating marine debris (>1cm) in the southeast Atlantic Ocean between Cape Town and Tristan da Cunha, crossing the southern edge of the South Atlantic ‘garbage patch’ predicted by surface drift models. Most litter was made of plastic (97%). Detection distances were influenced by the size and buoyancy of litter items. Litter density decreased from coastal waters off Cape Town (>100 itemskm−2) to oceanic waters (<10 itemskm−2), and was consistently higher (6.2±1.3 itemskm−2) from 3 to 8°E than in adjacent oceanic waters (2.7±0.3 itemskm−2) or in the central South Atlantic around Tristan (1.0±0.4 itemskm−2). The area with high litter density had few seaweeds, suggesting that most litter had been drifting for a long time. The results indicate that floating debris is accumulating in the South Atlantic gyre as far south as 34–35°S.
Understanding how rapidly seabirds excrete or regurgitate ingested plastic items is important for their use as monitors of marine debris. van Franeker and Law (2015) inferred that fulmarine petrels ...excrete ∼75% of plastic particles within a month of ingestion based on decreases in the amounts of plastic in the stomachs of adult petrels moving to relatively clean environments to breed. However, similar decreases occur among resident species due to adults passing plastic loads to their chicks. The few direct measures of wear rates and retention times of persistent stomach contents suggest longer plastic residence times in most albatrosses and petrels. Residence time presumably varies with item size, type of plastic, the amount and composition of other persistent stomach contents, and the size at which items are excreted, which may vary among taxa. Accurate measures of ingested plastic retention times are needed to better understand temporal and spatial patterns in ingested plastic loads within marine organisms, especially if they are to be used as indicators of plastic pollution trends.
Accurate estimates of the rates at which albatrosses and petrels wear down plastic items in their stomachs are needed if seabirds are to be used as indicators of marine debris.
•Very low concentrations offloating macro and microplastics found around Antarctica.•Mean densities of 0.03 macrolitter items·km−2 and 187.6 microplastics·km−2.•Plastic densities are one order of ...magnitude lower than in adjacent temperate waters.•The Subtropical Front seems to be a barrier to the dispersal of drifting plastics.
While macroplastics have been washing up on Southern Ocean islands for decades and microplastics have been found in seabirds from the region since 1960, there are still relatively few quantitative data on the amount of plastic pollution, especially with regard to floating plastics, at high southern latitudes. We present a baseline estimate of the abundance of floating plastics around the Southern Ocean from a survey of floating macro-, meso- and microplastic pollution conducted during the Antarctic Circumnavigation Expedition in 2016/17. A total of 40 net trawls and 626 h of observation were performed during this survey. Of these, 33 net samples and 552 h of observation were made in polar waters south of the Subtropical Front (STF). Only 5 microplastics and 17 macrolitter items were observed south of the STF, confirming the Southern Ocean as the region with the lowest concentrations of plastic pollution globally. The mean concentrations of floating macrolitter (0.02–0.03 items·km−2) and small plastic fragments (188 ± 589 particles·km−2) south of the STF were one order of magnitude lower than in adjacent temperate waters north of the STF, which suggests that the STF acts as a barrier to the southward transport of floating debris. Despite their much lower density, the mass of macroplastics was similar to that of floating microplastics in the Southern Ocean.
PDF
