Ingestion of Plastic Article

Abstract

Plastic marine debris is increasingly recognized as one of the greatest threats to global oceans, and the humans who depend on them. This study documents plastic ingestion in 24 species caught or sold for human consumption in the South Pacific. Fish were collected from local fishermen and markets in remote locations, including French Polynesia, Lord Howe Island and Henderson Island (Pitcairn group). Gastrointestinal tracts of 126 fish were visually examined and plastic was found in 7.9% of individual fish and 25% of species. The plastics were mostly microplastics (fragments, nurdles and rope). There was no significant difference in plastic ingestion in relation to feeding style, length, region or species. This is concerning as plastic appears to be widespread across species, lifestyles and habitats. This is the first report of plastic in South Pacific fish, raising concerns about the transfer of pollutants in a region that is largely oceanic and heavily dependent on seafood. The remote locations of the study also provide evidence of the widespread nature of this issue.

Introduction

Throughout oceans globally, there is a need for more research into the growing threats of plastic pollution, particularly regarding ingestion of anthropogenic debris by commonly eaten fish. Plastic is a significant concern for the oceans, threatening a diverse array of wildlife, from marine worms (Van Cauwenberghe et al. 2015) to whales (Besseling et al. 2015), and people (Van Cauwenberghe and Janssen 2014). In 2014, the amount of plastic in the oceans’ upper 10 cm was estimated to be at least 5 trillion pieces (Eriksen et al. 2014) and as plastic production increases so does the threat to marine life and communities who depend on the ocean (Rochman 2013). Physical harm by plastic debris, alongside the potential toxicity of plastics (through production as well as adsorption of pollutants in the environment) is a global problem (Sutherland et al. 2010). Plastics’ persistence in the environment, and the associated effects are likely to increase (Barnes et al. 2009); further research is therefore critical to understand how plastics are impacting the oceans, marine fauna, and people.

Microplastics are the most commonly found plastic debris, accounting for 92% of global marine plastics (Eriksen et al. 2014). Definitions of ‘microplastics’ vary slightly among researchers, but are defined by NOAA (National Oceanic and Atmospheric Administration) as particles < 5 mm in size (Wright, Thompson, and Galloway 2013). This includes primary microplastics (made for a specific purpose e.g. cosmetics), secondary microplastics (fragments resulting from environmental degradation of larger plastics) and nurdles (raw plastic pellets used in manufacturing) (Rocha-Santos and Duarte 2015; Eriksson and Burton 2003; Fendall and Sewell 2009; Andrady 2011).

There are at least 693 species recorded as encountering marine debris, including birds, marine mammals, turtles, fish, andmolluscs (Gall and Thompson 2015). The impacts of plastic marine debris include both lethal and sublethal effects, such as entanglement, ingestion, transport of invasive species, alteration of habitat, and introduction of pollutants (Gall and Thompson 2015). Animals consume plastic, presumably mistaken for prey items (Schuyler et al. 2014; Ryan 1987) or as a result of their opportunistic foraging strategy (e.g., surface scavenging seabirds) (Provencher et al. 2014). Microplastics are frequently ingested due to their small size, making them available for a range of animals, from plankton feeders to large filter feeding whales (Besseling et al. 2015; Fendall and Sewell 2009; Andrady 2011; Browne et al. 2008; Graham and Thompson 2009; Murray and Cowie 2011; Setala, Fleming-Lehtinen, and Lehtiniemi 2014; Wright, Thompson, and Galloway 2013). Laboratory studies have shown the potential for plastic particles to bioaccumulate in marine fauna (Setala, Fleming-Lehtinen, and Lehtiniemi 2014; Murray and Cowie 2011; Farrell and Nelson 2013).

Ingested plastics can introduce pollutants into the food web (Phillips and Bonner 2015). The pollutants associated with plastic have two major sources: those that are inherently bonded to the plastic as a result of the manufacturing process production (e.g. bisphenol-A (BPA), phthalates, polybrominated diphenyl ethers (PBDEs)), and those that sorb onto the plastics when they are in aquatic environments (e.g. persistent organic pollutants (POPs) such as PCBs, pesticides and dioxins) (Rochman, Hoh, Hentschel, et al. 2013; Rios, Moore, and Jones 2007; Teuten et al. 2009). Additives can be transported from microplastics into tissues in fish and worms by sorption into the gut after ingestion (Rochman, Hoh, Kurobe, et al. 2013; Browne et al. 2013; Rochman, Tahir, et al. 2015). Controlled laboratory studies have shown ingestion of microplastic particles transferring PBDEs into amphipods and fish (Chua et al. 2014; Wardrop et al. 2016). Pollutants may transfer to humans when fish or molluscs are ingested (Rochman, Hoh, Kurobe, et al. 2013; Browne et al. 2013; Rochman, Tahir, et al. 2015).

Plastic has been found in many commonly eaten fish species, causing concern in areas such as the South Pacific where fish is a vital food source (Rochman, Tahir, et al. 2015; Bell et al. 2009; Çelik and Oehlenschläger 2007). Plastic ingestion by fish was first recorded in the 1970s (Carpenter 1972), however until recently very little was known about which species were affected, and how severely. There are now records of >100 species of fish, rays and sharks containing some plastic (Sanchez, Bender, and Porcher 2014; Oliveira et al. 2013; Boerger et al. 2010; Davison and Asch 2011; Foekema et al. 2013; Choy and Drazen 2013; Anastasopoulou et al. 2013; Rochman, Tahir, et al. 2015). In Indonesia and the United States, 25-28% of fish sold at markets contained anthropogenic debris (primarily synthetic and natural fibres) (Rochman, Tahir, et al. 2015).

Globally, studies have been undertaken in many of the world’s oceans and waterways, primarily in the Northern hemisphere (Davison and Asch 2011; Carpenter 1972; Lusher, McHugh, and Thompson 2013; Anastasopoulou et al. 2013; ; Boerger et al. 2010; Foekema et al. 2013; Romeo et al. 2015). While there are some southern hemisphere studies (Di Beneditto and Awabdi 2014; Cliff et al. 2002; Ramos, Barletta, and Costa 2012; Cannon, Lavers, and Figueiredo 2016), research is lacking in the South Pacific and no data is currently available on South Pacific fish intended for human consumption. Given the concentration of plastics in the South Pacific gyre, it is also likely present in South Pacific fish (Eriksen et al. 2013; Martinez, Maamaatuaiahutapu, and Taillandier 2009). Pollution and waste management are one of the main issues facing the South Pacific region, particularly in the face of modern development (SPREP 2016).

Fisheries provide a huge industry as well as a vital food source for many nations, with over 128 million tonnes of fish eaten in 2010 (at a total value of US$217.5 billion) (Pulvenis 2012). Fishing (primarily subsistence fishing for reef and inshore fish) is a major source of food security in Pacific Island nations, both through providing a primary food source in many areas, and generating income (Charlton et al. 2016). An overview by Bell et al. (2009) found that subsistence fishing was responsible for 50-90% of fish consumed in rural areas in South Pacific countries. This number is likely to be higher in more isolated locations, for example, 92% of annual fish consumption on Ouvea Island (New Caledonia) was recorded as subsistence (Léopold, Ferraris, and Labrosse 2004). Overall, fish consumption is extremely high in the South Pacific in comparison to other nations, for example in 2013 in Polynesia total fish consumption was 37.6 kg/capita/year, relative to 13.2 in Europe and 6.2kg in the Americas (Pulvenis 2012).

Ingestion of plastic by fish has been confirmed in several species (Sanchez, Bender, and Porcher 2014; Oliveira et al. 2013; Boerger et al. 2010; Davison and Asch 2011; Foekema et al. 2013; Choy and Drazen 2013; Anastasopoulou et al. 2013; Rochman, Tahir, et al. 2015), however there are very few studies linking marine debris in fish with direct human consumption (Rochman, Tahir, et al. 2015). While South Pacific food fish have not previously been studied directly, in other locations several commonly eaten species have been recorded with ingested plastic such as tuna (Romeo et al. 2015), (Rochman, Tahir, et al. 2015; Choy and Drazen 2013), rabbitfish (Rochman, Tahir, et al. 2015), scad (Rochman, Tahir, et al. 2015) and mahi mahi (Phillips and Bonner 2015) This research provides a first pass study of plastic pollution ingestion by fish in the South Pacific. It identifies the presence of plastic in some commonly eaten fish, as well as an initial assessment of the characteristics of ingested plastic in this region.

Materials & Methods

Data collection

Samples of fish (126 total samples) were collected from May-August 2015 (Henderson Island, N=71), October 2015 (Lord Howe, N=21), April-May 2016 (French Polynesia, N=34) from local fishermen who were intending to eat the fish themselves, or sell at local markets (Figure One). All fish examined were intended for human consumption and were caught using hook and line fishing methods. The entire gastrointestinal tract was collected and analysed. Fish were identified to species level by local fishermen and with confirmation from fishbase.org, with photos taken to assist with further identification. Gotesson (2012) was used to assist with translating fish names from local identification to species level. Locations in French Polynesia were grouped due to proximity into western French Polynesia (Moorea, Fakarava, N=7) and eastern French Polynesia (Marquesas, N=27).

Figure One. Locations of sampling in the South Pacific. Fish were collected from local fishermen or fish markets (intended for human consumption) from June to August 2015 (Henderson), October 2015 (Lord Howe Island) and May 2016 (French Polynesia). From left to right, the locations are Lord Howe, western French Polynesia (Moorea, Fakarava), eastern French Polynesia (Marquesas), Henderson Island (Pitcairns). 1cm=~300km. Map from Google Maps (2016).

Analytical Methods

The gastrointestinal tracts (GITs) were analysed in the field, by visual examination (down to 1mm) by hand in a bowl of salt water (to aid plastic floatation). The salt water was filtered through a 0.4mm tea strainer prior to floating the plastic. Due to the remote nature of the fieldwork, techniques such as dissolving the intestinal tract (Rochman et al., 2015), or using a stereomicroscope (Foekama et al., 2013) were not plausible. Both the stomach and intestines were checked. Details of colour, size and type were recorded for each piece of plastic removed. The pieces were washed and dried and identified by a minimum of three observers to prevent confusion of plastic with organic material.

In order to analyse if feeding style impacts on plastic ingestion, fish species were assigned to trophic levels and guilds, as designated in (Alonso et al. 2015)), as well as feeding location. Two fish were excluded due to insufficient data. Trophic levels are numbers from one (primary producers) to four (apex predators), which were grouped into 3 variables – low (less than or equal to 2; N=25), medium (2.1 – 3; N=7), high (3.1 +; N=92) to improve analysis. Trophic guilds are simplified categories, including Algal Feeders (A; N=31), Invertivores (I; N=52) and Piscivores (P; N=41). This was based on the main source of food and with information and assignments from fishbase.org as well as actual observations made. Where multiple trophic guilds were potentially applicable, one guild was chosen based on the primary dietary source observed in the field. For example, Kuhlia sandvicensis are recorded as eating fish and invertebrates (P / I), however all identifiable stomach contents were crabs, carapace pieces and other crustaceans and therefore they were designated as Invertebrate eaters (I). Fish were also categorised based on length - S (<300 mm), M (300-500 mm), L (>500 mm) and location.

To test for significant differences in ingestion of plastic by commonly eaten fish, analyses were performed using R-Studio (version 0.99.893). Individuals that were not identified to the species level were removed from the analysis. Various factors were related to the rate of plastic ingestion using a generalised linear model (GLM) with a binomial distribution. This method has been used previously to analyse debris ingestion by sea turtles and birds (Burnham and Anderson 2003; Casale et al. 2016; Avery-Gomm et al. 2016). The package MuMIn was used to measure variables against the model of best fit. The Second-order Akaike Information Criterion (AICc) was used due to small sample sizes, as discussed in Burnham and Anderson (2003).

Results

Plastic was found in 25% of species (6 out of 24) and 7.9% of individuals (10 out of 126) from across the South Pacific (Figure Two). Of the more common fish species (> 10 individuals), 9.7% contained plastics. 60% of plastic was found in the intestines (not stomach).

Figure Two. Fish species analysed in the South Pacific. The amount of fish caught (total on y axis) as well as amount containing plastic (red).

From Henderson Island, 71 fish across 9 species were examined (Table One). Overall, 8 out of 71 individuals (11.3%) contained plastic in their gastrointestinal tract. Of the 9 species, plastic was found in the GIT of 4 (44%) including Christmas wrasse (1 out of 4 fish), coronation grouper (3 out of 15 fish), reticulated flagtail (3 out of 15 fish) and surge wrasse (1 out of 2 fish). One reticulated flagtail contained two microplastic pieces.

Table 1. Regions of plastic ingestion by fish in the South Pacific. The number of individual animals collected in each study location, and the number that contained anthropogenic debris

In Eastern French Polynesia, 2 out of 27 fish (7.4%) contained plastic. Of the 6 species, plastic was found in 2, the daisy parrotfish (1 out of 4 fish) and the blackfin barracuda (1 out of 7 fish). In Western French Polynesia 7 fish of 6 species were examined, none of these fish contained plastic. From Lord Howe Island, 21 fish across 3 species were examined, none of which contained plastic. Plastic debris was found in a variety of fish with differing habitats and feeding styles, however no significant factors were identified to predict plastic ingestion. The factors analysed included trophic level (delta: 2.4; AICc: 55.3), trophic guild (delta: 5.13; AICc: 58), feeding location (delta: 8.01; AICc: 60.9), region (delta: 8.01; AICc: 63.8) and fish length (delta: 4.88; AICc: 73). There were no models that fit the data better than the null model, and therefore none of the variables tested can be definitively linked to plastic ingestion (Figure Three).

Figure Three. Influential factors on plastic ingestion for South Pacific fish. A) Trophic level (Low, Medium, High); B) Trophic guild (A-Algal Feeders, P-Piscivores, I-Invertivores), C) Feeding location (Surface, Mid, Deep, Benthic); D) Region (Eastern French Polynesia, Henderson Island, Lord Howe Island, Western French Polynesia); E) Size (small<300 mm, medium 300-500 mm, large >500 mm). Red= contains plastic, blue=no plastic detected. Total: 124 fish (2 were not analysed due to lack of classification data).

Properties of ingested plastic All anthropogenic debris found in the fish was plastic, and all were microplastics with the exception of the synthetic rope fragment (2cm long). Ten individual pieces were detected; six fragments (blue, white, black), three nurdles (black, white) and one rope fragment (green). The predominant colour of the plastics was blue (40%), followed by white (30%), black (20%) and green (10%).

Discussion

This research shows that there is some evidence of plastic ingestion by commonly eaten South Pacific fish in remote locations. While more research is needed into this area, there are still useful conclusions to be made from the data. Plastic has been found in fish of all trophic levels (from herbivores to apex predators), life stages (larvae, juvenile and adult) and several habitat types (sea grass, reefs, pelagic, coastal), although the types of plastics may differ. Previous studies have found that some ecological considerations can predict the risk of plastic ingestion for species of fish, such as habitat and feeding preferences, however there were no predicting factors evident in this study (Rochman, Tahir, et al. 2015; Hoss and Settle 1988; Possatto et al. 2011). The occurrence of plastic was not significantly different between locations, species, or based on feeding styles.

The amount of plastic found (in 7.9% of individual fish, and 25% of species) is likely an underestimate of true plastic levels. Additionally, local anecdotal data, conversations with fishermen during April/May 2016, suggest that mahi mahi do ingest plastic pieces. One fisherman in Fakarava (Tuamotu group) had observed 3 large plastic pieces in the stomachs of Coryphaena hippurus in the past year – this included 2 Coca Cola bottle caps, and one large blue mayonnaise lid. While the variation in methods used across fish ingestion studies negates direct comparison, the amount of individual fish containing plastic may be up to 60% (Van Noord, Lewallen, and Pitman 2013) but is more commonly 5-15% (Dantas, Barletta, and da Costa 2012; Davison and Asch 2011; Jackson, Buxton, and George 2000; Phillips and Bonner 2015; Ramos, Barletta, and Costa 2012). However it is important to keep in mind that there is a wide range of analyses used both in the collection of samples, and detection of plastic pieces.

Additionally, due to limitations on methods imposed by the remoteness of this study’s locations it is likely that the plastic encountered is only a fraction of what is present. It does not account for pieces smaller than 1 mm, and was also limited in the species available for collection. If more detailed analysis was possible much higher amounts of plastic are likely due to the inclusion of microfibres and microbeads which are extremely prevalent in global oceans (Eriksen et al. 2014; Isobe 2016; Rochman, Kross, et al. 2015; Fendall and Sewell 2009) and have been detected in fish ingestion studies (Lusher, McHugh, and Thompson 2013; Possatto et al. 2011; Rochman, Tahir, et al. 2015; Dantas, Barletta, and da Costa 2012; Tanaka and Takada 2016). The ingestion of plastic by fish can cause several problems, both directly (through blockage or injury) and indirectly (through introducing harmful pollutants into the individual, and the food chain). This data clearly demonstrates that a range of South Pacific fish are ingesting plastic, which may have important health concerns for the many people who depend on fish as part of their diet. All of the fish in this study were collected from local fishermen or markets, and therefore are certainly being consumed. While many species are gutted prior to consumption, there are still potential negative health impacts due to pollutants introduced to the fish tissue by plastic ingestion. Additionally, in some island locations smaller fish are eaten whole and not gutted. While more research is required to determine the extent and impact of this contamination, it is clear that toxins can be transported by plastic, and potentially have a range of negative impacts (Rochman, Tahir, et al. 2015; Rochman, Hoh, Kurobe, et al. 2013; Wardrop et al. 2016; Engler 2012; Phillips and Bonner 2015).

Factors influencing ingestion

This report documents the first recorded ingestion of plastics by species spanning the South Pacific Ocean and first records for the Pitcairn group and French Polynesia. This is also the first record of ingestion by surge wrasse, reticulated flagtail, Christmas wrasse, coronation grouper, bullethead parrotfish, and barracuda. Based on records from other locations, along with feeding and habitat characteristics, it is extremely likely that other commonly eaten South Pacific fish species are also ingesting plastic pieces, such as mahi mahi, several tuna species, whiting and flying fish (Romeo et al. 2015; Choy and Drazen 2013; Phillips and Bonner 2015; Foekema et al. 2013). Mahi mahi (Coryphaena hippurus) often concentrate near marine debris, both natural and man-made, enhancing their chances of encountering and ingesting marine debris. While the single mahi mahi obtained for this study did not contain plastic, anecdotal evidence documented three large plastic pieces in one year from one fisherman in Western French Polynesia. Plastic was also found in mahi mahi in the north Pacific (Choy and Drazen 2013) and Gulf of Mexico (Phillips and Bonner 2015).

Regional variation was not significant in this study, however this may be a result of disparity in sample sizes. There are many factors that influence geographic distribution of plastic pollution, such as amount of waste, rubbish management, ocean gyres & currents, and proximity to populated areas (Phillips and Bonner 2015). The large amount of ingested plastic in fish from Henderson Island (11.3%) is particularly concerning, due to the distance from urban centres and other common outputs of marine debris. Despite predictions and models suggesting the South Pacific would have lower amounts of marine debris, many coastal studies observed similar densities to the northern hemisphere (Bravo et al. 2009; Hinojosa, Rivadeneira, and Thiel 2011; Eriksen et al. 2013). The main sources of marine debris in the South Pacific Subtropical Gyre (SPSG) are the surrounding coastal margins, including aquaculture and beach / shore based activities, and transport of plastic by the SPSG across the equator as well as from local sources (Eriksen et al. 2013) (Lebreton, Greer, and Borrero 2012). Henderson Island has some of the highest densities of plastic marine debris on any beach in the world (Lavers and Bond 2017). Regions with higher amounts of plastic are likely to result in fish with increased plastic ingestion.

Globally, there is a large gap regarding research into the exposure of fish to plastic pollution, with just 0.68% of fish species reported as encountering marine debris (compared to 56% of seabirds and 54% of marine mammals) (Gall and Thompson 2015). This gap likely reflects the focus of studies, rather than actual plastic presence, as plastic ingestion studies of fish have been mostly opportunistic (Gall and Thompson 2015). It is evident that more research is needed to provide a clearer picture of which species are being impacted.

Plastic characteristics

Of the ten plastic pieces found in fish stomach or intestines, six were fragments, three nurdles, and one rope fragment (technically all microplastics, excluding the rope fragment). Large scale studies of surface plastics frequently record microplastics and fragments as the most common type encountered(Shaw and Day 1994; Eriksen et al. 2014) It is likely that ingestion by fish and other animals is one of the main ways in which plastic debris is relocated, both by passing into higher level predators, and being removed from the sea surface (e.g. sinking in faecal pellets) (Eriksen et al. 2014). While direct comparison is negated by differing methods, the types of plastic found in this study (60% fragments, 30% nurdles, 10% rope) are similar to those found in fish gastrointestinal tracts from other locations(Davison and Asch 2011; Lusher, McHugh, and Thompson 2013). Small fragments made up 57% of total plastic in North Pacific fish (Davison and Asch 2011), and were the second most common item detected in English Channel species (Lusher, McHugh, and Thompson 2013). Additionally, the methods used excluded some smaller and more difficult to identify items (such as fibres and clear film) but may have favoured more buoyant items (such as nurdles) (Davison and Asch 2011; Boerger et al. 2010). This may explain the ratio of nurdles to fragments (3:6), which is higher than that found in other ingestion studies.

Nurdles, or the virgin resin pellets used as industry feedstock, account for 30% of the plastics found inside fish. They may resemble common prey items such as fish eggs and more research is required into whether they are consistently a commonly ingested item(Cousin et al. 2015; Lusher, McHugh, and Thompson 2013). As plastic production does not take place on any of the study sites, and most of the studied fish are not migratory, it is clear that the nurdles were transported to the island locations by current and wind from larger industrial centres. They may have been lost from ships transporting the pellets to factories for production, or potentially from land-based sources such as manufacturing sites.

Ingestion of particular colours, types and sizes of plastic may reflect plastic production, or alternatively a preference by the fish for certain characteristics. The plastics were mostly blue (40%) and white (30%) as well as black (20%) and green (10%). It is unknown whether this is a reflection of available plastics, or a preference by the fish. Carson (2013) found that certain types and colours of plastic were chosen preferentially by marine organisms such as fish; yellow and blue. Accumulation of biological organisms on the surface of the plastic may also influence ingestion rates (Reisser et al. 2013; Romeo et al. 2015).

While assessing provenance of microplastics is difficult due to their small size, there are some pieces that can be traced to certain industries or locations. The green piece of rope is most likely debris from the fishing and boating industry, as it appears to come from a large piece of synthetic green rope of the type often found on ships. This is likely to be an extremely common form of waste in the South Pacific, where fishing vessels are very prevalent and shipping is listed as a significant source of marine pollution, with over 92,000 vessel movements in 2013 (SPREP 2016).

Impacts of ingestion

Ingestion of marine debris is a pathway for potentially harmful pollutants to be introduced to individual fish, as well as the larger food chain (Chua et al. 2014). Plastic is directly ingested by fish, particularly microplastics, resulting in desorption of pollutants into the animals tissue (Engler 2012). Plastic itself contains several chemical additives, such as BPA, phthalates and PBDEs, and further accumulates POPs and heavy metals such as DDT, PBDEs and mercury, while in the ocean (Holmes, Turner, and Thompson 2012; Engler 2012). Ingestion of plastic can transfer chemicals such as PBDEs and POPs into fish tissue (Wardrop et al. 2016) (Browne et al. 2013; Chua et al. 2014). Pollutant levels also increase as a result of continued exposure to plastics in the gastrointestinal tract (Wardrop et al. 2016). Therefore even small amounts of plastic, like the ones documented in this study, may be transporting large amounts of pollutants into fish and other marine animals, potentially impacting on multiple species across the South Pacific. In their high trophic position, humans may be ingesting fish tissue that has been contaminated by POPs and other plastic-related contaminants.

Once plastic has been ingested, the physical pieces may cause harm and even accumulate inside the organism (Lavers, Bond, and Hutton 2014; Farrell and Nelson 2013; Setala, Fleming-Lehtinen, and Lehtiniemi 2014). The residency time of plastic in fish is unknown, and probably varies by species and age of organisms, and type and size of particle (van Franeker and Law 2015; Ryan 2015). Captive experiments found plastic ingestion by fish was linked to decreased body condition, reduced mass, less effective predation, and decreased fitness (Danner, Chacko, and Brautigam 2009; Carlos de Sa, Luis, and Guilhermino 2015). Chemicals linked to the plastic may also be harmful to individual fish health, for example by altering endocrine function and causing liver toxicity (Rochman et al. 2014; Rochman, Hoh, Kurobe, et al. 2013). This decreased condition is particularly relevant in a region so highly dependent on fish consumption in their diet.

It is also worth noting that the large amount of plastic present in ocean environments, in comparison to the relatively small amount found in South Pacific fish, supports the idea that many fish are passing the plastic pieces. The ability of fish to expel plastics is corroborated by laboratory studies showing some fish species can pass the plastic pieces (Hoss and Settle 1988). Furthermore, 60% of plastic pieces in this study were found in the intestines (not stomach). Inclusion of the intestines has not been done in all studies (Davison and Asch 2011) however is recommended in order to get a more accurate view of ingestion 3. Potentially this short residency time could decrease exposure to toxins and chance of translocation from alimentary tract to tissue (Phillips and Bonner 2015). This raises questions regarding the residence time of plastic in the alimentary tract, ability of pollutants and additives to transfer from plastics to fish tissue (shown to occur by Wardrop et al, 2015) and the transport of plastic in faecal matter (potentially relocating buoyant plastics to the sea floor, as previously documented in zooplankton faecal pellets) (Cole et al. 2016).

Planning & management

This research has many implications for future planning and policies of both waste management, and human health. The inaugural United Nations Environment Assembly in 2014 adopted the Marine Plastic Debris and Microplastics Resolution, calling upon the global community to urgently recognize the significant impacts of marine debris, and begin to implement solutions. This is of particular importance in the South Pacific, which is 98% ocean and extremely dependent on ocean ecosystems and yet currently have no national budgets for marine litter management (SPREP 2016). The presence of plastic in South Pacific fish adds weight to the need for wider recognition of this issue. Additionally, Henderson Island (where most ingested plastic was found) is UNESCO World Heritage Listed due to its environmental importance, and as a result the large levels of plastic pollution and negative impacts of marine debris should be a cause for concern. The wider risk, to both South Pacific and global consumers of seafood, also requires recognition and action.

Conclusions

Food fish of the South Pacific are ingesting some plastics, particularly microplastics. The evidence of plastic is concerning, particularly as there appears to be no predicting factors, and plastic is found across a range of species with varied lifestyles and habitats. This study provides an initial assessment, as well as first records of plastic ingestion in these locations and in several species of fish. Currently there is no way to predict which species are more at risk, and what factors are the most important determinants of plastic ingestion. More studies are required, but it also is important to consider that plastic ingestion is extremely widespread, both taxonomically and geographically. Future studies should use more in-depth techniques (such as those described by Rochman et al., 2015) and identify smaller plastic particles (down to 100 µm) (Phuong et al. 2017).

The presence of plastic raises a number of issues regarding pollutants, particularly in regards to how these pollutants may be transferred to the humans ingesting these fish. This issue is extremely relevant to the South Pacific, where inhabitants are heavily dependent on fish and seafood is exported for consumption globally. Very little information is currently available for the South Pacific region on marine litter, and more research is necessary to implement national strategies and policies. Furthermore, no funding is currently allocated to management of marine litter in the South Pacific. This research highlights the need for greater understanding and action on the issue of plastic pollution in global oceans.

Acknowledgements

The authors would like to gratefully acknowledge assistance received from the following people and organisations. Marcus Haward, Alex Bond, Angus Donaldson, Anthony Wilson, Craig (Macca) Wilson, Ian Hutton, Jack Shick, Jennifer Lavers, Lorna McKinnon, Moana and Richard Friedman, Nicolee Woods, Pawl Warren, Royal Society for the Protection of Birds, Save Our Shearwaters Foundation, Sue O’Keefe, Titouan Bernicot and family, Trading Consultants LTD, Vaughan Wellington.

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