Today, plastic polymers have a widespread usage in the production of almost every material we use in our daily lives. As a natural consequence of this excess production, a lot of plastic waste was generated. Unfortunately, due to improper waste management practices and low recycling rates (OECD, 2022), generated plastic waste ends up in aquatic environments (Figure 1). Recent study showed that more than 80% plastic debris in oceans derives from terrestrial environments and is transported via rivers (Wang et al., 2024). Once plastics reach aquatic environments, they break down into small particles under the influence of several physicochemical and biological reactions (Manzoor et al., 2022) and are called secondary MPs. Alternatively, primary MPs were within micro size to be used in personal care products (An et al., 2020).
Sources of MPs in environment together with fate and transport mechanisms
So far, the presence of MPs was reported in almost all ecosystems including the deepest part of the ocean ( Peng et al., 2018) to extremely rural polar regions ( Kelly et al., 2020). Once microplastic particles reach the aquatic environment, they become biologically available to aquatic organisms from different trophic levels due to their small size and association with plankton in the water column ( Harmon et al., 2024). Entrance of MPs in the animal’s body threatens the animal’s wellbeing by causing oxidative stress, inflammation, reducing immune responses, altering feeding and behavior ability, leading to toxicity and neurotoxicity ( Yang et al., 2021). Since widespread and abundant presence of MPs had reached a level that endangered ecosystem health, legal regulations began to be formed on the subject. First, Marine Strategy Framework Directive (MSFD-EU, 2008/56/EC) targets achieving a good environmental status that was described as “The amount of litter and microlitter ingested by marine animals is at a level that does not adversely affect the health of the species concerned” in the descriptor 10.
Seafood is a vital part of the human diet due to its high nutritional value. Aquaculture facilities are extremely important in meeting this demand without hindering the sustainability of the ecosystems. As a result, world aquaculture production continues its growth and total production reached 87.5 million tons of aquatic animals for human consumption in 2020 (FAO, 2022). On the other hand, consumption of microplastic-containing seafood creates concern regarding human health. For that reason, the World Health Organization made an official call for the determination of sources, occurrence, and exposure levels of MPs ( WHO, 2019).
Due to global concerns, microplastic presence in the aquaculture systems and farmed species recently gained a lot of attention from scientists and policy makers. Besides, aquaculture facilities are usually located at the sheltered coastal regions or rivers ( Wu et al., 2020; Nabi et al., 2024) where received MPs are trapped due to transport kinetics ( Onink et al., 2021). Therefore, understanding the sources, presence and exposure levels of MPs is necessary to take necessary precautions. By doing so, the aquaculture sector will continue to growth without any concerns regarding human health.
So far, majority of the previous studies have focused on microplastic presence in wild aquatic animals and general recommendations. Differently, the fecal point of the study was exploring the microplastic contamination status of aquaculture facilities to provide comprehensive data for future legislations. Within the scope of the study, microplastic occurrence rates and microplastic abundance in aquaculture facilities and aquaculture animals were determined. Bibliometric analysis and discussion regarding potential sources of MPs in the sector were also included.
A detailed literature research for peer-review articles was followed with Web of Science (WoS) database in July 2024. Within the scope of the study, studies evaluating the microplastic presence in the aquaculture facilities were the major focus. Below strings were followed during research.
TS=(“micro$plastic” OR “microplastic$” OR “plastic$”) AND TS=(pollut* OR monitor* OR digest* OR ingest* OR litter* OR occurrence) AND TS=(aquaculture).
This search yielded 456 articles on 01/07/2024. After removing duplicate articles and performing the necessary screening procedures, a total of 106 articles published between 2016 and 2024 were evaluated; 90 of these were research articles and 16 were review articles. Within the scope of the paper, only research articles were used in the literature review and they were further divided into two categories depending on their focal point (as environment or biota).
Academic journals that have been published in the previous reports of microplastic contamination in aquaculture facilities were researched to evaluate the prevalence of this topic in the scientific community. So far, research findings of previous studies were published in 42 different academic journals. The highest number of articles was published in Science of the Total Environment (17 articles), followed by Marine Pollution Bulletin (15 articles), Environmental Pollution (7 articles), Journal of Cleaner Production (5 articles) and Frontiers in Marine Science (4 articles) ( Figure 2 A).
Results of bibliometric analysis: (A) The number of publications by journals, (B) Word cloud of keywords in publications, (C) Contribution network of the countries, and (D) Number of published studies by years
Keywords used in articles play an important role in expressing the main content and highlighting key research directions in a field. Keywords from 106 MPs studies were counted and visualized by font size based on their density. The most frequently used keywords in the articles were “MPs (s)” and “Aquaculture”, which were used 58 and 40 times, respectively. In addition, terms such as Pollution (7), Bivalvia (6), Plastic Pollution (7), Fish (9), Bioaccumulation (5), Health Risk (5) and Food Safety (5) were also found to be frequently used keywords ( Figure 2 B).
The interest of the academic community in a certain issue is generally parallel to the economically important industrial activities and current environmental policies of the country. A total of 707 researchers from 34 different countries contributed to the writing of 106 articles. According to the countries to which the authors belong, the Republic of China contributed the most, publishing 38 articles. This is followed by Spain (8 articles) and Italy (5 articles) ( Figure 2 C). Thailand, Greece, Portugal and Indonesia were also among the contributing countries. In some papers, authors from more than one country collaborated; for example, there were four collaborative papers with China, Norway, Iran, USA (California) and Italy ( Figure 2 C). Publication distributions by country showed that more studies have been performed in leading countries of aquaculture industry.
It is known that anthropogenic activities increase the microplastic load to aquatic environments ( Heard, 2024). Besides, MPs are trapped in the coastal regions due to marine transport kinetic ( Onink et al., 2021). This condition is alarming because aquaculture activities usually take place in the described environments (coastal regions or rivers), where microplastic abundance was higher. In addition, these facilities are usually located in shelter regions where MPs tend to accumulate ( Wu et al., 2020). All this knowledge proves that the location of the aquaculture facility is an important parameter while determining potential remediation techniques
Entrance of MPs into aquaculture facilities could be external (land base sources, atmospheric transport) or internal origin (aging of plastic fishing gears, feed) ( Wu et al., 2023).
The majority of the MPs found in the aquatic environments was attributed to the land base sources. Among all, stormwater runoff is a major pathway of MPs into aquatic environments ( Werbowski et al., 2021). A recent study revealed that contribution of stormwater runoff to the microplastic load of streams was higher than other external sources ( Cho et al., 2023). MPs found in the stormwater runoff are highly associated with the land use in the region. For example, in urban environments, high proportion of MPs in the stormwater runoff consists of road wear particles, tire wear particles and asphalt particles (Grbić et al., 2020). On the other hand, in urban environments, MPs dominantly originate from agricultural activities. The plastic mulching, usage of plastic pipes in irrigation, fertilization applications ( He et al., 2022) and application of greenhouse films ( Qi et al., 2023) lead to accumulation of MPs in the soil which is transported to aquatic environments with stormwater runoff.
Domestic and industrial wastewater contribute significantly to the microplastic loads of aquaculture ecosystems. Among industrial wastewater, the textile industry is one of the leading contributors to the microfibers and could carry notable amount of microfibers to the aquatic environments ( Chan et al., 2021) that increase the microplastic load in the surrounding environment ( Deng et al., 2020). So far, presence of MPs in the wastewaters of marine construction plants ( Franco et al., 2020), packaging industry ( Sezer et al., 2024), industrial estates and parks ( Franco et al., 2020; Barkmann-Metaj et al., 2023), agricultural industry (i.e. livestock farms) ( Wang et al., 2020) were reported. Similarly, municipal wastewater contains fibers from laundry ( Wang et al., 2024), micro-pellets from cosmetics, toothpaste and shampoo ( Jiang et al., 2018). Studies showed that even though high microplastic removal could be achieved by advance wastewater treatment practices, millions of MPs are discharged to aquatic environments from wastewater treatment plants on daily basis (Kılıç et al., 2023).
MPs found in the effluents of the aquaculture facilities ( Wang et al., 2020) could also originate from the aquaculture activities. In the aquaculture facilities, polyolefin, polyethylene, polyamide, nylon are commonly used in the production of fishing nets, ropes and fishing gears ( Koongolla et al., 2020; Carus et al., 2017). These plastic products generate MPs due to aging and wearing processes ( Wu et al., 2023). Besides, oxidizing disinfectants and bacteriostatic agents employed in this industry could increase the weathering rate of MPs ( Hu et al., 2020; Ma et al., 2019 ; Yu et al., 2023). Aquacultured animals could also lead to formation of MPs by fish nibbling ( Reinold et al., 2021), crab climbing and pinching ( Xiong et al., 2021).
The second major source of MPs in aquaculture facilities is feed. Siddique et al. (2023) reported microplastic abundance in the fish feeds produced in Bangladesh. They found that all the examined feed samples contained MPs and the lowest and highest mean number of MPS were reported as 500 MPs/kg to 2200 MPs/kg. Gündoğdu et al. (2021) evaluated the microplastic abundance in obtained fish feed samples from 11 different countries (Antarctica, Chile, China, Denmark, India, Morocco, Mauritania, Norway, Peru, South Africa, South Korea and Türkiye) and reported values ranging from 0 to 527 MPs/kg. Wang et al. (2022) obtained fish feeds from different countries (United States, Denmark, Myanmar, Mauritania, Mexico, Chile, Peru, Panama, China and Russia) and mean MPs abundance in the feed were reported as 5500±1600 MPs/kg. Similarly, Walkinshaw et al. (2022) evaluated the presence of anthropogenic particles including MPs and they reported the presence of 1070–2000 anthropogenic particles per kg of fish feed. In general, fiber shape and small size MPs (less than 1 mm) were common ( Siddique et al., 2023; Wang et al., 2022). Coherent to the general picture, widely used polymers such as PE, PP, PET, PP were common in fish feeds ( Siddique et al., 2023; Wang et al., 2022).
Similar to other aquatic environments, MPs are widely present in the aquaculture systems. Majority of the studies conducted so far have been focused on microplastic abundance in the surface water or sediment of marine or freshwater environments. Only a small proportion of studies evaluated the microplastic abundance in the aquaculture environments.
Microplastic abundance in the different aquaculture systems (i.e. aquaculture ponds, cage systems, RAS) have been reported. Mean MPs abundance in the surface water varied from
0.036 item/m3 to 103800 items/m3 in aquaculture pond,
2526 items/m3 to 0.31 item/m2 in the cage farming, and
1530 to 1670 items/m3 in RAS.
High variation in the reported values could be related with the aquatic environment where facility is located (i.e. marine or riverine), farmed species (fish, crap, mussel etc.), employed methodology differences in the isolation of microplastics, hydrodynamic properties ( Le et al. 2021), feed source or anthropogenic influences near the aquaculture farm ( Wang et al., 2017).
Since aquaculture pond facilities are artificial environments, their microplastic abundance is directly influenced by the design of ponds. Recent studies demonstrated that earthen and cement ponds contain considerably higher amounts of MPs than RAS systems ( Huang et al., 2023). More effective filtering in the RAS systems provides remarkable improvements in the reduction of MPs ( Xiao et al., 2023, 2019). Similarly, employed infrastructure in the system had an important role in the formation of MPs. Fattening farms, fencing equipment, nets, ropes and pipes made up of plastic materials are generally used in aquaculture facilities ( Xiong, 2021; Zhu et al., 2019; Wu et al., 2020; Feng et al., 2020), which act like a source of secondary MPs. Previous studies mentioned the formation of secondary MPs during fish nibbling ( Reinold et al., 2021), crab climbing and pinching ( Xiong et al., 2021). Therefore, it can be said that behavior of farmed species might also cause variations in the MPs abundance.
As an ultimate sink, MPs present in the surface water accumulate on the bottom sediment. Mean microplastic abundance in the sediment of aquaculture facility varied between 73 items/kg to 4765 items/kg in the literature ( Table 1). This variation could be explained by the variations in the study area, employed equipment, feed, adopted methodology, taxa and hydrodynamic factors such as seasonality. In general, during turbulent flow conditions, sinking rate of MPs is reduced, MPs accumulated on the sediment might resuspend and transport with the currents. Conversely, during laminar flow conditions, transportation of MPs from surface water to sediment increases due to biofilm formation caused by high nutrient conditions in the pond ( Chen et al., 2019; Xiong et al., 2021).
Literature summary regarding microplastic abundance in aquaculture environments
| Location | Environment (Water or Sediment) | MP abundance | Main color | Main shape | Main size (µm) | Polymer | References |
|---|---|---|---|---|---|---|---|
| Vancouver Island, Canada | Water | 0.63±0.68 MPs/L | Blue | Fiber | 1000−5000 | Covernton et al., 2019 | |
| Sediment | 19.97±23.74 MPs/kg | Clear | Fiber | 1000−5000 | |||
| Ionian Sea | Water | Film, Fragment | 1000−5000 | PE, PS, EAA, EVA, PEO, PP | Miserli et al., 2023 | ||
| Cadiz, Spain | Water | 9.54±6.81 MPs/L | Fiber | PE, PP, HDPE | Egea-Corbacho et al., 2023 | ||
| Lianyungang, China | Water in pond aquaculture | 6.47±0.30 MPs/L | Black-gray | Fiber | 0–1000 | CP, PE, PP, PET, PS, PVC, PA, PMMA, PAM, PTFE | Song et al., 2023 |
| Water in industrial aquaculture | 2.06±0.59 MPs/L | Black-gray | Fiber | 0–1000 | PET, PE, PP, CP, PA, PAN | ||
| Yangtze River Delta, China | Water | 4.4–10.8 MPs/L | Blue | Fiber | 1000−3000 | PE, PET, PP, PS, PE | Yu et al., 2023 |
| Sediment | 0.286–0.543 MPs/g dw | Blue | Fiber | 100–300 | PE, PET, PP, PS | ||
| Lianyungang, China | İnland aquaculture mode | 6.03±4.95 MPs/L | Black-gray | Fiber | PE, PP, PET, PA, PS, PAN, PVC, PTFE, PAM | Song et al., 2024 | |
| Marine aquaculture pond | 2.37±1.83 MPs/L | Blue-green | Fiber | PET, CP, PE, PP, PS, PA, PP-PE, PVC, PEU | |||
| Coastal aquaculture mode | ~4.0±2.0 MPs/L | Black-gray | Fiber | PE, PET, PA, PP, PS, PVC, PTFE, PEU, PAN | |||
| Portugal | Water, RAS | 6.10±2.33 MPs/L | Black | Fiber | 150–499 | cellulose/rayon, phenoxy resins, PAM, nylon, PET, PAN, PTFE | Matias et al., 2024 |
| Fiji Island | Water | 2.9 ± 0.4 MPs/L | Fiber | 500−900 | nitrile, nylon, PE, PP, PU, PVA, PVC | Dehm et al., 2022 | |
| Sediment | 0.022 ± 0.01 MPs/g dw | Fiber | 500−900 | nitrile, nylon, PE, PP, PU, PVA, PVC | |||
| Malaysia | Water | 1.28±0.15 MPs/L | Transparent | Fiber | 50−500 | Nylon, PE, PS, PP | Hossain et al., 2023 |
| Sediment | 47.5±11.875 MPs/g | Transparent | Fiber | 1000−5000 | |||
| China | Water | 5.82±0.75 MPs/L | Fiber | 500−1000 | PET, CP, PE, PA, PP, PE/PP | Du et al., 2022 | |
| Thailand | Water | 41.5±6.0 MPs/L | Fragment | 50−300 | HDPE, PET, PS, PES, Ethylene/propylene copolymer | Imasha and Babel, 2022 | |
| Sediment | 474.6±102.6 MPs/kg | Fragment | 50−300 | HDPE, LDPE, linen, PET, PP |
MPs found in the surface water and sediment of aquaculture ponds were primarily attributed to the anthropogenic influences such as urbanization, industrialization ( Wang et al., 2017; Debnath et al., 2024), riverine waters ( Le et al., 2021), rain triggered surface runoff ( Hossain et al., 2023), transport of plastic trash through current and eddies ( Anjeli et al., 2024). On the other hand, recent studies showed that aquaculture ponds magnify the microplastic pollution load in the surrounding environment ( Xiong et al., 2021). Zhu et al. (2019) reported that marine aquaculture facilities contribute more than 70% to the MPs load of marine environments.
MPs isolated from aquaculture areas create a general picture with the dominance of fiber shaped, small size MPs (<1000 µm) from both surface water and sediment ( Table 1). Previous studies reported the presence of 24 different polymers in the surface water and/or sediment of aquaculture areas. Among them, PE, PP, PET, PS, PA and PVC were the major polymers and followed by PAM, PTFE, HDPE, PAN, CP. Other polymers like CPE, PMMA, PEU, EVA, EAA, PU were reported in few studies in small proportions ( Table 1).
Previous studies have revealed that MPs are omnipresent in all aquatic environments even in the ones untouched by humans. As a consequence of this, aquatic organisms interact with these tiny particles. Potential entrance pathways of MPs were reported as (i) absorption through the gills, (ii) ingestion through consumption, and (iii) direct adhesion of MPs to organisms (de Sá et al., 2018; Öztürk and Altınok, 2020; Aydın et al., 2023).
So far, 35 different studies were conducted to understand the microplastic contamination levels in the aquacultured species. Majority of the examined studies were focused on fish species (n=19 studies), followed by mollusks (n=17 studies), crustaceans (n=4 studies). So far, species from other taxa have not been the focal point of microplastic research. Statistical analysis revealed a significant variation in the mean microplastic abundance between fish, bivalves and crustaceans (Kruskal Walis test, P<0.05) ( Figure 3). That is an expected outcome consi dering the bioecology of these species. For example, filter feeding species were reported to be more vulnerable to microplastic pollution (McNeish et al., 2018; Alomar et al., 2022) ; while shrimps and fish may show selective feeding behavior that might reduce (Wu et al., 2023) or increase the microplastic accumulation rates depending on the ambient environment. For example, pelagic fish species might confuse light colored MPs with plankton that increase the likelihood of ingestion ( Güven et al., 2017). Similarly, a recent study reported the preference of black colored particles in younger fishes ( Atamanalp et al., 2022) that could increase the microplastic ingestion potential. Even though the latter two studies employed wild specimens, the latter two assumptions could also be valid for cultured specimens since bioecology of the animal was independent of the ambient environment.
Microplastic abundance in the digestive organs of aquacultured species
Microplastic abundance in the aquacultured fish species was mainly studied in Mediterranean countries and China. In terms of taxa, fish species from Cyprinidae, Gobiidae, Sciaenidae and Serenidae families were commonly employed. Among them, Sparus aurata (n=7) and Dicentrarchus labrax (n=7) were the most studied species in Mediterranean countries, while Plectropomus leopardus (n=4) was the most studied species in China.
The majority of previous studies were focused on microplastic accumulation levels in the digestive organs. Gills were the second most studied organs ( Feng et al., 2019; Lin et al., 2022; Aiguo et al., 2022; Zhou et al., 2024), yet other organs such as muscle ( Yu et al., 2023, Aiguo et al., 2022) or skin ( Feng et al., 2019) took lesser attention.
Microplastic occurrence rate in the digestive organs of farmed fish species varied between 33% and 100%. The lowest frequency of occurrence was reported in Dicentrarchus labrax from Spain (Sánchez-Almeida et al., 2022); whereas, 100% occurrence was reported in Oreochromis niloticus from Colombia ( Garcia et al., 2021) and Spain (Blonç et al., 2023). The average microplastic abundance in the digestive organs was reported to be 0–58 MPs/individual and 0.01–546 MPs/g (wet weight) ( Figure 3). Median of mean microplastic abundance in the digestive organs was estimated as 2.48 MPs/individual. Statistical analysis showed no significant difference in the mean microplastic abundance depending on habitat or feeding habit of the species (Kruskal-Wallis test, P>0.05). Similarly, no correlation was observed between MPs abundance and trophic level of the species. In fact, these results are not surprising since employed specimens live in controlled environments. For that reason, the differences in the reported values probably related with the external factors such as employed aquaculture technique ( Matias et al., 2024), feed ( Siddique et al., 2023), season ( Du et al., 2022) or methodological differences. Besides, age seems to be an effective internal factor impacting the microplastic ingestion rate of fish ( Savoca et al., 2021).
Studies revealed that MPs could penetrate through other organs prior to ingestion ( Egbeocha et al., 2018) or adhere to the skin ( Feng et al., 2019). Egea-Corbacho et al. (2023) reported the presence of MPs in the muscle of Dicentrarchus labrax. Similarly, Blonç et al. (2023) investigated the MPs presence in the different organs of Oreochromis niloticus. They found polyethylene particles in the digestive system, polyethylene, polysiloxane, polydimathysiloxane particles in the muscle, perhydropolysilaxane particles in the brain. Presence of different polymer types in the latter study supports the idea that polymer type is an important factor in the interstitial migration of MPs ( Bronç et al., 2023). This is a significant finding and hides the actual health risk of contaminated fish consumption. Future studies should be focused on the identification of specific polymers that translocate into edible tissues in order to develop sustainable and contamination-free aquaculture industry.
When the second most studied phylum, mollusca, was examined, the focal point of previous reports was bivalvae class. Previous reports were commonly conducted in Mediterranean countries (n=5), Thailand (n=3), China (n=4). In these studies, Mytilus galloprovincialis (n=5), Perna viridis (n=4), Magallana gigas (n=2) were the most studied species. Besides species in bivalvae class, there is only one study examining the microplastic abundance in the digestive organs of a cephalopoda, Sepia officials from Portugal ( Oliveira et al., 2020).
Previous studies showed that nearly all examined bivalve species contained MPs in their soft tissues. Mean microplastic abundance in the bivalve class changed from 0.1 to 12.6 MPs/individual and median of the reported values was estimated as 1.8 MPs/individual ( Table 2). Recent studies showed that the size of bivalves is positively correlated with MPs ingestion rate. In other words, as the age of mussel or clam increases, MPs content in the soft tissues also increases ( Imasha and Babel, 2023 ; Ruangpanupan et al., 2023). This is attributed to the higher filtration rates of smaller mussels ( Imasha and Babel, 2023). In addition to soft tissues, Chen et al. (2023) investigated the MP content of oyster shells and reported the mean microplastic abundance as 0.74 MPs/g. This proves that MPs could penetrate through bivalvae’s shells by participating in the biomineralization process. In that sense, shells become the ultimate sink for the MPs and create environmental concerns regarding microplastic pollution (Chen et al., 2023).
Literature summary regarding microplastic abundance in biota from aquaculture facilities
| Phylum/Class | Location | Species | FO (%) | MPs/ind | MPs/g | Main color | Main shape | Main size (µm) | Polymer | References |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| Mollusca/Bivalvae | Xiangshan Bay | Ostrea denselamellosa | 66.7 | 1.67±0.44 | 0.31 (ww) | Fiber | 500−1000 | Cellulose (main), PA, | Wu et al., 2020 | |
| Sinonovacula constricta | 80.0 | 1.8±0.34 | 0.21 (ww) | Fiber | 0−500 | acrylonitrile, PP, PE, PET | ||||
| Canada | Venerupis philippina | 0.10±0.10 | 0.16±0.18 (dw) | Clear-blue | Fiber | 100−500; | PP, polyolefin, PES, nylon | Covernton et al., 2019 | ||
| Crassostrea gigas | 0.13±0.16 | 0.02±0.03 (dw) | Clear-blue | Fiber | 500−1000 | |||||
| Baynes Sound, British Columbia | Venerupis philippinarum | 8.4±8.5 | 1.7±1.2 (ww) | Colourless | Fiber | Davidson and Dudas, 2016 | ||||
| Hainan, China | Perna viridis | 0.36±0.81 | White | Foam | <1 mm | PS, PE | Lin et al., 2022 | |||
| North Ionian Sea | Mytilus galloprovincialis | 16±1.7 | PE, EEA, EVA | Miserli et al., 2023 | ||||||
| Thailand (from market) | Tegillarca granosa | 11±5 | 1±0 | Fiber, Fragment | 0.05–0.3 | PP, PE, PP, PES | Ta et al., 2022 | |||
| Perna viridis | 96±19 | 4±0 | 0.05–0.3 | |||||||
| Thailand (from farm) | Tegillarca granosa | 6±1 | 1±0 | Fiber, Fragment | 0.05–0.3 | PE, EP, PE, PES | ||||
| Perna viridis | 11±7 | 3±2 | 0.05–0.4 | |||||||
| Malesina, Greece | Mytilus galloprovincialis | 5.00±0.96 | Fiber | PET, PP, PE | Manolaki et al., 2023 | |||||
| Pinctada imbricata radiata | 2.55±0.83 | |||||||||
| Spain | Mytilus galloprovincialis | 94 | 5.68±0.72 | Transparent | Fiber | Cellulose acetate, styrene-acrylonitrile, PES, LDPE, PET | Alomar et al., 2022 | |||
| Todos Santos Bay, Mexico | Magallana gigas | 100 | 1,30 | Black, Blue | Fiber | >1000 | PET, PAN, rayon, PA, PP, PS | Lozano-Hernández et al., 2021 | ||
| San Quintin Bay | 100 | 0.85 | ||||||||
| Haizhou Bay | Mercenaria mercenaria (inland) | 97 | 12,6363636 | Black-gray | Fiber | <1000 | PET, PEU, PP, PVC, CP, PAN, PE, PA, PTFE, PAM, PS, PP-PE | Song et al., 2023 | ||
| Scapharca broughtonii (inland) | 100 | 10,6333333 | ||||||||
| Ruditapes philippinarum (coastal) | 100 | 6,90322581 | ||||||||
| Meretrix meretrix (coastal) | 100 | 7,36666667 | ||||||||
| Ruditapes philippinarum (marine) | 100 | 4,86666667 | ||||||||
| Scapharca broughtonii (marine) | 85 | 3,46666667 | ||||||||
| Bohai Sea, China | Crassostrea gigas | 94 | 2.92±0.10 | 0.36±0.02 (ww) | Fiber | 500–1000 | CP, PET | Du et al., 2022 | ||
| Sriracha farm, Thailand | Perna viridis | 3.2±1.6 | 2.4±0.8 (ww) | Fragment | 50–300 | HDPE | Imasha et al., 2023 | |||
| Phetchaburi, Thailand | 1.2±0.2 | 0.3±0.1 | Fragment | <0.3 mm | HDPE, PP, PES, linen, PET, PVC, ethylene/propylene copolymer | |||||
| Türkiye | Mytilus galloprovincialis | 2.28±0.67 | 1.33±0.86 | Black | Fiber | 0.1−0.5 | EPDM, EP, PS, PMP, PA, PET. | Tunçelli and Erkan, 2024 | ||
| Thailand | Crassostrea belcher | 0.53–1.42 | Fiber | 0.5−1 mm | CP, PE, PET, PP, PS, PVC, nylon | Ruangpanupan et al., 2023 | ||||
| Perna viridis | 0.17–0.31 | Fiber | 0.5−1 mm | CP, PE, PET, PP, PS, PVC, nylon | ||||||
| Tegillacar granosa | 0.33–1.01 | Fiber | 0.5−1 mm | CP, PE, PET, PP, PS, PVC, nylon | ||||||
| Mollusca/Cephalopoda | Ria Formosa lagoon system | Sepia officinalis | 11–45 | 0.86±0.34 (dw) | Fiber | PP, LDPE, HDPE | Oliveria et al., 2020 | |||
| Sepia officinalis | 27–52 | 2.14±1.10 (dw) | Fiber | PP, LDPE, HDPE | ||||||
| Arthropoda/Crustacea | Lianyımgang | Penaeus vannamei | 100 | 10–18 | 1–2 | Black-gray | Fiber | <1000 micron | CP, PET, PE, PP, PA, PS, | Song et al., 2024 |
| Penaeus vannamei | 100 | 8–18 | ~ 1 | Black-gray | Fiber | PVC, PTFE, PMMA, PAM | ||||
| Yangtze Estuary, China | Chinese mitten crabs | 100 | 23.9± 15.9 | Blue | Fiber | 100−300 | PE, PP, PET, PS | Yu et al., 2023 | ||
| Mexico | Litopenaeus vannamei | 32.3±3.1 | 2.0±0.3 | Transparent | Fiber | PE, nylon, PET, PS, PP, PA | Valencia-Castañeda et al., 2024 | |||
| Xiangshan Bay | Parapenaeopsis hardwickii | 45.0 | 0.95±0.28 | 0.25 (ww) | Fiber | 500−1000 µm | PA, acrylonitrile, PP, PE, PET | Wu et al., 2020 | ||
| Vertebrata/Teleostei | Xiangshan Bay | Larimichthys crocea | 80.0 | 1.8±0.42 | 0.01 (ww) | Fiber | 0−500 µm | PA, acrylonitrile, PP, PE, PET | Wu et al., 2020 | |
| Konosirus punctatus | 90.0 | 2.1±0.38 | 0.04 (ww) | Fiber | 0−500 µm | PA, acrylonitrile, PP, PE, PET | Wu et al., 2020 | |||
| Muara Kamal, Jakarta Bay | Chanos chanos | 3,005 | 9.58±3.3 | Fiber | Priscilla and Patria, 2019 | |||||
| Marunda, Jakarta Bay | Chanos chanos | 2.09 | 8.80±2.7 | Fiber | ||||||
| Laizhou Bay | Oplegnathus punctatus | 1.50±0.58 | 0.21±0.14 (ww) | Blue | Fiber | 20–500 μm | PA, PET, PP, PE, PVC, PS, PMMA | Zhou et al., 2024 | ||
| Laizhou Bay | Oplegnathus punctatus | 2.25±0.96 | 0.48±0.22 | Blue | Fiber | 20–500 μm | PA, PET, PP, PE, PVC, PS, PMMA | |||
| Laizhou Bay | Plectropomus leopardus | 1.50±1.73 | 0.17±0.21 | Blue | Fiber | 20–500 μm | PA, PET, PP, PE, PVC, PS, PMMA | |||
| Laizhou Bay | Plectropomus leopardus | 3.00±1.83 | 0.19±0.14 | Blue | Fiber | 20–500 μm | PA, PET, PP, PE, PVC, PS, PMMA | |||
| Dingzi Bay | Epinephelus cyanopodus | 2.25±0.96 | 0.50±0.38 | Blue | Fiber | 20–500 μm | PA, PET, PP, PE, PVC, PS, PMMA | |||
| Dingzi Bay | Epinephelus cyanopodus | 2.75±1.71 | 0.07±0.08 | Blue | Fiber | 20–500 μm | PA, PET, PP, PE, PVC, PS, PMMA | |||
| İskenderun Bay | Oncorhynchus mykiss | 63 | 1.2±1.3 | Black | Fiber | 1–2.5 mm | PES, PA, PE | Kılıç, 2022 | ||
| İskenderun Bay | Sparus aurata | 50 | 0.8±1.1 | Black | Fiber | 1–2.5 mm | PES, PA, PE | |||
| Seyhan and Ceyhan | Dicentrarchus labrax | 52 | 0.95±1.1 | Black | Fiber | 0.3−0.5 mm | PES, PA, PE | |||
| Hainan, China | Siganus guttatus | 58±2.9 | White | Foam | <1 mm | PS, PE, PET, PVC | Lin et al., 2022 | |||
| Plectropomus leopardus | 0 | |||||||||
| Trachinotus ovatus | 0 | |||||||||
| Canary Island, Spain | Dicentrarchus labrax | 65 | 1.43+1.75 | Blue | Fiber | Cellulose, nylon, PE, PP | Reinold et al., 2021 | |||
| North Ionian Sea | Dicentrarchus labrax | 22±2.1 | Fiber | LDPE, PVB, PBMA, PE | Miserli et al., 2023 | |||||
| Sparus aurata seabream | 40±3.9 | Fiber | LDPE, PVB, PBMA, EVA, PVA | |||||||
| Beibu Gulf | Trachinotus ovatus | 546±52 | Blue or Green | Pellet, Fragment | 20−200 | PE, PA, PU | Liu et al., 2023 | |||
| Spain | Sparus aurata | 33 | 2.03±0.30 | Transparent | Film | HDPE, LDPE, PE | Alomar et al., 2022 | |||
| Canary Islands, Spain | Dicentrarchus labrax | 5.4±4.2 | Colourless | Fiber | PES, PAN, PEUR | Sánchez-Almeida et al., 2022 | ||||
| Sparus aurata | 5.1±5.1 | Colourless | Fiber | |||||||
| Huila, Colombia | Oreochromis niloticus gill | 0.375 | Fragment | PE, PET | Garcia et al., 2021 | |||||
| Oreochromis niloticus gut | 2,125 | PES, PE, PET | ||||||||
| Oreochromis niloticus flesh | 0.25 | PET, PP | ||||||||
| Mediterranean Sea, Greece | Sparus aurata | 38 | 0.51±0.78 | Black | Fiber | PP, PES, EP, PA | Mosconi et al., 2023 | |||
| Italy and Croatia | Sparus aurata | 1.30 | Black | Fiber | 1−2 mm | PES, PE, PTFE, PAA, PA | Savoca et al., 2021 | |||
| Cyprinus carpio | 0.25 | Blue | Fiber | <1000 micron | PES, PE, PTFE, PAA, PA | |||||
| Turkish waters of the Aegean Sea | Dicentrarchus labrax | 89,13043478 | 3.2±2.3 | 0.18±0.13 | Blue-black | Fiber | Man-made cellulose/ray-on, PET, phenoxy resin | Matias et al., 2024 | ||
| NE Atlantic coast of Portugal | Dicentrarchus labrax semi-intensive | 94 | 4.2±2.8 | 0.53±0.40 | Black | Fiber | Phenoxy resin, man-made cellulose/rayon | |||
| Portugal | Dicentrarchus labrax | 96,36363636 | 4.89±2.50 | 0.69±0.42 | Black | Fiber | Man-made cellulose/rayon, PVC, PET | |||
| Fiji Island | Oreochromis spp. | 2.7±1.4 | Fiber | <1 mm | PE, PP, PU, PVA, PVC, nylon | Dehm et al., 2022 | ||||
| Guangzhou, Guangdong China | Ctenopharyngodon idella | 93 | 13±8.569 | 0.601 | Blue | Fiber | 0.5−2 mm | Olefins, acrylic, rayon, PES, PP, PE | Aiguo et al., 2022 | |
| Hypophthalmichthys molitrix | 92 | 9.083±4.699 | 0.556 | Blue | Fiber | 0.5−2 mm | ||||
| Cirrhinus molitorella, | 88 | 11±10.985 | 0.891 | Blue | Fiber | 0.5−2 mm | ||||
| Oreochromis niloticus | 93 | 9.357±7.143 | 1.436 | Blue | Fiber | 0.5−2 mm | ||||
| Pelteobagrus fulvidraco | 91 | 6.909±4.182 | 3.354 | Blue | Fiber | 0.5−2 mm | ||||
| Haizhou Bay, China | Thryssa kammalensis | 22.21±1.70 | Black-gray | Fiber | 0−1000 μm | CP, PP, PE, nylon, PET | Feng et al., 2019 | |||
| Amblychaeturichthys hexanema | 18 | Black-gray | Fiber | 0−1000 μm | CP, PP, PE, nylon, PET | |||||
| Odontamblyopus rubicundus | 16 | Black-gray | Fiber | 0−1000 μm | CP, PP, PE, nylon, PET | |||||
| Cynoglossus semilaevis | 13.54±2.09 | Black-gray | Fiber | 0−1000 μm | CP, PP, PE, nylon, PET | |||||
| Chaeturichthys stigmatias | 15 | Black-gray | Fiber | 0−1000 μm | CP, PP, PE, Nylon, PET | |||||
| Collichthys lucidus | 15 | Black-gray | Fiber | 0−1000 μm | CP, PP, PE, nylon, PET |
There are 4 studies investigating microplastic abundance in the culturalized crustacean species from China (4) and Mexico (1). Penaeus vannamei and Mierspenaeopsis hardwickii from Penaeidae family and Eriocheir sinensis from Varunidae family were examined in the previous studies. Mean microplastic abundance in the digestive organs varied from 0.95 to 40.3 MPs/individual and median of the previous reports were found as 17.00 MPs/individual. Previous reports revealed that larger size crustaceans contain a higher amount of MPs ( Valencia-Castañeda et al., 2024; Song et al., 2024), probably due to the higher encounter risk of MPs resulting from increase in the uptake ( Song et al., 2024). Additionally, it is noted that microplastic abundance in digestive organs differs depending on employed aquaculture systems ( Song et al., 2024).
Microplastic abundance was also reported in gills and hepatopancreas of aquaculture crabs Eriocheir sinensis ( Yu et al., 2023). A recent study showed that ingested MPs might form fiber tangles in the hepatopancreas of crustaceans that could pose a serious threat to the well-being of these species (Yücel, 2023).
Shape is an important morphological property that determines the bioavailability of MPs ( Wang et al., 2020). Previous studies showed that fiber-shaped MPs have higher bioavailability compared to other shapes ( Wang et al., 2020). Besides, fiber-shaped particles were found to be dominant in the surface water and sediment of aquaculture farms as well as fish feed. Coherent to those, fiber-shaped MPs were common in almost all published articles ( Table 2).
Forty different polymers were reported to be isolated from the aquacultured species. Among those, polyethylene was the most common polymer reported in 70% of published articles. According to reported studies, the most reported polymers could be listed as follows: PP, PET, PES, PS, PA, PVC ( Table 2). Their presence in the aquatic biota is generally attributed to the anthropogenic influences.
Studies revealed that accumulation and translation potential of MPs vary depending on the type of the polymer (Blonç et al., 2023). Even though 40 different polymers were identified in the literature, lab studies evaluating the impacts of MPs on marine biota only employed 10 different polymers, primarily PS, PE, PU ( Casagrande et al., 2024). Potential causes of these polymers were identified as inflammation in gills and GIT, kidney and liver damage, oxidative stress, glycogen depletion, cell necrosis, reproductive abnormality and so on ( Dayal et al., 2024).
Due to the connection between fisheries products and humans by food web, microplastic containing aquaculture products also carry a concern for human health. Previous studies revealed that microplastic exposure could cause disturbances in human chromosome sequences, metabolic disorders like obesity, infertility or even cancer ( Laskar and Kumar, 2019). More studies should be carried out to better understand the potential causes of MPs on aquatic biota and the human body.
Study results clearly showed the widespread presence of MPs in aquaculture systems that is similar to other aquatic environments in the world. Previous studies conducted on the topic highlight the importance of location, employed infrastructure and feed in evaluating the microplastic presence in aquaculture facilities. Besides, literature indicates that animals’ behavior could play a significant role in the formation and distribution of MPs. Findings were handy in determining the potential sources of MPs; however, it should be noted that methodological differences in the analysis of ısolation of MPs from biota could cause variations in the reported abundance values. In future studies, usage of standardized methodology is necessary to understand microplastic contamination levels by eliminating under or overestimation potential. Besides, lab scale studies should be designed considering the polymer type and prioritization should be given to unexamined polymer types. That will increase the understanding of potential implications of MPs on aquatic biota.
Although the exact contribution of seafood consumption to microplastic uptake in humans is not fully understood, the findings of this study revealed that consuming seafood offers a route for microplastic intake via the food chain. To better assess the quality and safety of aquaculture products, the relationship between MPs and aquaculture products and their potential harmful effects on human and environmental health should be clarified. This will help the formation of necessary measures to control the introduction of MPs into the aquaculture environment. Among potential alternative mitigation methods, adaptation of aquaculture infrastructure with bio-based plastic products seems to be a promising solution of this problem. Besides, it is important to prevent transport of plastic waste into aquatic environments by implying plastic waste management and removal actions. In this way, it is possible to sustain economic growth of the industry while eliminating current concerns regarding human health.