in number.
The average amount of microplastic fibres per 1000 m3 present in the surface water is 568±
264 with an average filtered volume of 16,91±1,79 (see Appendix 12 “Surface Water Sample Standard Deviation” and graph below).
4.3 Microplastic Fibres in Boops boops
For the second trophic level the table below shows the results of microplastic
presence in the representative species Bogue. B. boops stomachs showed microplastic in all of the investigated specimens. The amount of microplastic fibres ranges from 12 to 20 as the table below shows.
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Table 2 Microplastic Fibres Present in B. boops
Sample
The colouration of fibres differs between black, blue, red, transparent, green and others. In number, black and transparent are the most abundant with 26 and 24 (see Appendix 5 “B.
boops Microplastic Fibres Presence”). The average weight is 76 ± 7.4, the average length is 19,4 ± 0.8 and average number of fibres is15,4 ± 3,2 in this species (see Appendix 13,15 and 17). The average fibres per weight are 204 ± 49,9 and fibres per length are 79 ± 16,9 (see Appendix 14 and 16).
4.4 Microplastic Fibres in Trachurus mediterraneus
T. mediterraneus represents the third trophic level of the investigation. The analysis of the T. mediterraneus stomachs showed presence of microplastic ranging from 14 to 62 pieces (see table below).
Table 3 Microplastic Fibres in T. mediterraneus
Sample Weight Length Total Fibres
Fibres per
The fibre colouration within these individuals ranges from blue most numerous, black second highest to yellow with the lowest as shown in the Appendix 7 “T. mediterraneus Microplastic Fibres Presence”. The first individual had the most fibres present. The four other specimens have one third the number of fibres than the first (see table above). The average weight is
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175,4 ± 43,9, the average length is 27 ± 3,1 and average number of fibres is 28 ± 19,5 (see Appendix 13,15 and 17). The average fibres per weight are 157 ± 173,1 and fibres per length 101 ± 86,2 (see Appendix 14 and 16).
4.5 Microplastic Fibres in Sphyraena viridensis
The S. viridensis stomach all contained micro fibres and the amount of fibres range from 23 to 75 (see table below).
Table 4 Microplastic Fibers Present in S. viridensis
Sample Weight Length
Total Microplastic
Fibres per Length (m)
Fibres per Weight (kg)
S.v. 1 229 37 35 95 153
S.v. 2 1750 74 75 101 43
S.v. 3 656 56 48 86 73
S.v. 4 390 53 23 43 59
S.v. 5 819 62 30 48 37
Average 769 56 42 75 55
All kinds of fibre colours are present in the investigated species. The highest amount of microplastic was found in the second individual. It also contains the highest amount of black and transparent fibres see Appendix 9 S. viridensis Microplastic Fibres Presence. The average amount of fibres in this species is 769 ± 594,3 weight, 56 ± 13,5 of length and 42 ± 20,5of total fibres. The average fibres per weight are 55 ± 46,9 and fibres per length 75 ± 26,9.
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4.6 Overall Food Chain
Figure 19 Correlation Length And Number of Fibres
Figure 21 Correlation Weight and Number of Fibres
Comparing weight and length of the average species in the food chain shows that there is a positive correlation between weight or length and the number of fibres due to the correlation coefficient (R) being high (almost 1) in both cases. The fibres per weight and weight show a negative correlation. Contrary to that the fibres per length and specimen length show little correlation due to the correlation coefficient being low (see Figure 20). The graphs above show also that the number of fibres is higher whenever fish are heavier or taller. Conversely the ratio of fibres to length/ weight is greater in smaller fish. This correlation implies that the hypothesis of this investigation, that consumption per gram of lower trophic level fish is more harmful than of higher levels is correct.
y = 1.2292x0.8901
Fibres per Length (m)
Length (cm)
Fibres per Length
Figure 18 Correlation Length and Fibres perLength
y = 2765x-0.582
Figure 20 Correlation Weight and Fibres per Weight
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5 Discussion
As previously shown, the results attested to the presence of microplastic in all trophic levels of the investigated food chain. The results show that partly there is a correlation in size or weight of the species and amount of fibres found in the investigated species. This
supports the statement made in the hypothesis that the consumption of an individual higher trophic level fish is more harmful than an individual lower level species due to greater microplastic presence. Moreover the presence of a greater number of fibres found in higher trophic levels is arguably evidence for the bioaccumulation of microplastic in the food chain of the yellowmouth barracuda, and thus marine ecosystems. The bioaccumulation of microplastic in this food chain in which ultimately humans are the final consumer indicates that microplastic fibres do indeed pose a very serious threat to human health, particularly in maritime areas of heavily pescetarian diet.
5.1 Sample Period and Location
The samples were all taken around Samos Island and the fish are highly likely to travel along the whole coastline even though some samples were taken in the north and some in the south of the Island. The samples were taken over one and a half months, with the exception of zooplankton samples which were taken latest due to the weather conditions;
strong wind, currents or waves. This might have influenced the amount of fibres found because the weather conditions changed significantly from strong winds and 20°C to a moderate climate. Due to this change in conditions the water temperature increased which might have had an influence on the activity of the fish and with that the possibility of ingesting microplastic fibres was higher.
5.2 Correlation Between the Total Fibres and Length/ Weight
The occurring differences in the standard deviations could be caused by different day of catch, location of catch, sex, low difference between size and weight of the individuals.
The B. boops show a small standard deviation which could be a result of them being caught at the same day (see Appendix 4 “B. boops Information Samples”). These individuals were probably part of a fish school with similar eating and traveling behaviour. All those factors result in similar size/ weight and presence of fibres or other contaminants.
T. mediterraneus and S. viridensis standard deviation are much bigger which could be a result of the specimen being caught at different locations and days. This results in different of lifestyle. Though some fish were caught at the same day and showed similar characteristics (see Appendix 6 and 8).
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The findings show that there were more fibres present in the tested yellowmouth barracuda than in horse mackerel, bogue and surface water. This correlates with other research, which states that heavy metals, mercury, and pesticides accumulate within the food chain and are more highly concentrated in high trophic levels than in lower ones (Cresson, et al., 2014). It means that the highest trophic level of this investigated food chain have the most fibres compared lower trophic levels as the B. boops and T. mediterraneus. This correlates with the behaviour of other pollutants which accumulate in a food chain. Considering the average length, weight and amount of fibres also supports this test result. The smallest and lightest fish, B. boops, has the lowest amount of fibres and the tallest or heaviest fish, S. viridensis, has the highest amount.
On the other hand, the results show that the number of fibre per weight or length is higher in smaller or lighter specimens. This correlates with other studies which argue that herbivore accumulate higher concentrations of metals than carnivore species due to their feeding habit (El-Moselhy, Othman, El-Azem, & El-Metwally, 2014).
5.3 Quality Control During Research
The control sample shows little evidence of micro fibres with an average of 1,1 ± 1,2 which indicates almost no contamination from outside (see Appendix Control Sample). This insures the accuracy of properly conducted work. Contamination control measures were:
filtering the distilled water due to its storage in plastic containers; cleaning the needed equipment first with soap or alcohol and afterwards three times with filtered distilled water.
The occurring contamination could be a result of the atmospheric or the tank pollution. These sources of contamination were checked on weekly basis (see Appendix Quality Control).
Further contamination with fibres can result from the salt used for the salt solution which was packaged in plastic, or stirring due plastic coating of the stirring magnet which could erode (see appendix saltwater contamination). To counteract these interferences, every saltwater solution was filtered twice before for the analysis of microplastic fibres present in the fish stomach. Contamination with fibres might have occurred due to filtering the distilled water with contaminated filter paper though the rate of contamination decreased (see Appendix Quality Control). Due to the contamination of the new filter paper with which the distilled water from plastic containers was filtered, some contamination might have occurred. Though, the contamination of filter paper became less over the period of research see Appendix Quality Control, Filter Paper Contamination. Apart from the Surface water filter papers, but the threat of contamination wasn’t as high as from the others (see Graphs in the Appendix Quality Control, Filter Paper Contamination).
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5.4 Identification Problems of Microplastic Fibres
The report “A comparison of microscopic and spectroscopic identification methods for analysis of microplastic in environmental samples” by Young Kyoung Song et al., pointed out the discrepancies in the identification of microplastic fibres and other fibres (see figure below).
Figure 22 Pictures of natural fibres: (a) non-plastic (organic), (b) non-plastic (cotton) and (c) non plastic (rayon) and synthetic fibres: (d) and (e) impact polypropylene (Song, et al., 2015)
Therefore, it can only be assumed that the discovered fibres are from microplastic origin though it cannot be certain but is highly possible.
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5.5 Health Hazard For Human Food Resources
It is mentioned before, in the theoretical framework chapter, that fibres pose threats to organisms that consume them as they can cause blockage in the digestive tract, become translocated to different tissues within the organism, and undergo accumulation (Mathalon &
Hill, 2014). In reference to this regardless of being of plastic origin, fibres are a threat to the organisms that consume them. There is a health risk in fish from which the organs are not taken out and a possible health risk for other fish from which the organs are taken out due to the probability of fibres transferring into the tissue the surrounding tissue (Mathalon & Hill, 2014).
Assuming that the occurring fibres are from microplastic origin, there is also a threat by pollutants. Toxicants leaching out of the plastic debris might be introduced to organisms which were incorporated as additives while manufacture, to improve the properties of the plastic. But also due to their hydrophobic properties which leave them susceptible to accumulation of hydrophobic organic contaminant which could dissociate after ingestion (Cole, et al., 2013). This higher bioavailability of contaminants in the low trophic levels has an impact on the whole ecosystem. The coastal structure could be interrupted substantially and with that produce a trophic cascade and extinct species (Bacelar et al., 2008).
Furthermore, it is already proven that microplastic ingestion takes place in zooplankton species which act as the primary consumer. They are capable to ingest small plastic particles and also show clumping in the posterior mid-gut. This in turn has impact on their algal
ingestion which decreased significantly (Cole, et al., 2013). One effect could be
bioaccumulation of fibres in the food chain which makes micro fibres available for the higher trophic levels (Bacelar et al., 2008) which could be the reason for fibres occurring in the fish stomachs of S. viridensis, T. mediterraneus and B. boops. Another effect could be change in feeding behaviour and with that higher risk of infection or starvation and death which leads to a decrease in population.
As already mentioned, sudden regime shift and ecosystem collapses is more likely to occur in stressed ecosystems, due to top-down (e.g. overfishing) versus bottom-up (e.g. increase of nutrition input that causes eutrophication (Bacelar et al., 2008). All this might influence the availability for food resources for humans but also points out the risks for human health by eating fish containing fibres and other pollutants. Additionally, it shows that the health risk is higher when human eat high trophic levels which are fish like the yellowmouth barracuda or horse mackerel. Smaller fish on the other hand show an increased risk due to the higher amount of fibres per weight and length.
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6 Conclusion
The hypothesis of this study was to clarify the potential threat posed by microplastic fibres to ecosystem and human health. The data shows presence of fibres in all trophic levels of the S. viridensis food chain. The existing fibres in all trophic levels are a threat to the environment and human health. The possibility of clogging due to fibres makes organisms vulnerable to diseases and behavioural capabilities. As humans are consumers of bogue, mackerel and barracuda the continuation of humans to eat fish containing fibres may incur these health risks. This threat is all the more imminent considering that fibres bioaccumulate, thus humans as final consumers ingest a substantially large number of fibres from the ecosystem, particularly from the consumption of tertiary and quaternary consumers. Even though fibres are only analysed in the gut and stomach organs of the fish, which are removed before cooking, there is a risk that fibres and contaminants transfere into
sourrounding tissue. Undeniably ingestion of both the high and the lower trophic levels pose threats to human health. As although the fibres bioaccumulate and are greater in number further up the food chain the lower trophic levels showed a higher amount of fibres per weight or length. Consequently a diet containing either many small fish, such as bogue or mackerel or fewer higher level fish, like barracuda or bream is a threat to human health due to possible ingestion of microplastic fibres.
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7 Recommendation
Further researches are needed to ascertain the extent of the spread of microplastic fibres in particular. The research of this project was limited to the presence of fibres and not their composition. It is essential that further studies are undertaken with appropriate equipment which is able to distinguish microplastic fibres. Another limitation to the success of this research is the methodology used to collect microplastics of all densities. A number of methods were used which only allowed low density microplastic to be filtered out. This leads to discrepancies as high density particles escape the scientific record.
The investigation was restricted by having a limit in time to carry out the research. For more accurate research a bigger sample size is needed. In addition to this, the facilities at
Archipelagos, Institute for Marine Conservation, limited the extent to which research on microplastic presence could be carried out. The laboratory arguably lacked the essential equipment required to conduct coherent research. Distilled water is fundamental for accurate research this was a problem at the lab of archipelagos base due to the fact that there was no tap providing distilled water. Instead the distilled water was delivered in a plastic container which obviously risks contamination of plastic. To prevent this, measures as filtering the water had to be taken. Due to the lack of a tap, the proper practice of sanitation before handling equipment was infeasible. Although methods using strong alkaline, acidic and toxic solutions would have been the most effective, the lack of proper safety equipment made them impossible to be carried out; afore the mentioned tap and laboratory hood.
As a prevention measures to reduce the amount of microplastic entering the ecosystem, local people should be informed and advised on the correct disposal of waste and reduced plastic usage. Awareness should be spread to lower the risk to human health from the consumption of microplastic through this pathway.
It is important to minimise the previously mentioned harmful effects of microplastic.One way could be the implementation of the 5Rs (Refuse, Reduce, Reuse, Recycle, Rethink). The priority Rethink promotes the use of different materials and techniques, whereas Refuse, implements reducing the production of plastics. Ideally ecosystems would be cleaned of microplastic pollution. However, collecting all these particles would take forever and would not be effective. (Ivar do Sul & Costa, 2013). It is infeasible because of their residual global presence.
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To tackle the problem of microplastic pollution in the marine environment the European Commission introduced policies within the Marine Strategy Framework Directory
(2008/56/EC). These incentives for the reduction of the accumulation of plastic debris are appropriate at various levels encompassing governments, producers, retailers and the consumers. The implementation of legislation by the individual governments of the European Union enforces stricter disposal and sorting household and industrial waste. This signifies an appropriate shift to reusable products and reduction in the use of plastic (Thompson, 2006).
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