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Volume 33, Issue 5 (12-2024) |
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Microplastic contamination in the whitefish (Rutilus frisii) from the southwestern Coasts of the Caspian Sea (Guilan Province)
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Fereshteh Haji Aghaei Ghazi Mahalleh   , Javid Imanpour Namin1 |
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Abstract: (364 Views) |
Introduction
Plastics, despite their widespread applications and advantages across various industries, have become a significant environmental challenge due to their durability and persistence. Incomplete degradation of these materials in nature leads to the production of microplastics (plastic particles smaller than 5 millimeters), which pose severe risks to the health of living organisms, particularly aquatic species (Arthur et al., 2008). These particles, due to their physical properties such as density, size, and shape, disperse unevenly in aquatic environments, with some floating on the water surface while others sink to deeper layers (Anderson et al., 2017). Microplastics are transferred through the food chain, with planktonic organisms playing a pivotal role in their transfer to higher trophic levels (Setӓlӓ et al., 2014). Accumulation of microplastics in the bodies of organisms can lead to physiological damages such as digestive and reproductive disorders (Farrell and Nelson, 2013). These particles are classified into primary (e.g., microbeads in cosmetics) and secondary (resulting from the degradation of larger plastics) types (Gouin et al., 2015). The identification of polymer types in microplastics is typically achieved using FTIR-ATR spectroscopy, which, due to its high accuracy, serves as an effective tool for characterizing various plastic polymers (Li et al., 2020). Given the significance of the whitefish (Rutilus frisii) in the Caspian Sea ecosystem and its role as a biological indicator, this study aims to investigate microplastic contamination in this valuable species. The results of this research could contribute to a better understanding of the impacts of microplastic pollution on the Caspian Sea ecosystem and, consequently, on human health.
Methodology
The Caspian Sea, the largest enclosed lake in the world, with an area of 393,000 square kilometers and a coastline of 6,525 kilometers, is located between the continents of Asia and Europe, making it an important freshwater resource in the Eurasian region (Debus, 1995). Three stations with the highest potential for pollution were selected along the southwestern coast of the Caspian Sea for sampling: Kiashahr (impacted by the Sefid Roud River), Bandar Anzali (affected by the Anzali Wetland), and Bandar Astara (influenced by pollution inflows from Azerbaijan) (Kostianoy et al., 2005). Sampling of the Caspian Sea whitefish was conducted in March 2022 and April 2022, with 20 fish purchased from local fishermen at each station and transferred to the laboratory. In the laboratory, the biological characteristics of the fish, including their weight, total length, and standard length, were recorded. After dissection, the gastrointestinal tract was extracted and digested with a 10% potassium hydroxide solution (Rochman et al., 2015; Karami et al., 2017). Microplastics were identified and counted using a 40× light microscope (Abbasi et al., 2018). To identify the polymer type of the extracted microplastics, Fourier-transform infrared spectroscopy (FT-IR) with an attenuated total reflectance (ATR) crystal was employed (Veerasingam et al., 2021). Statistical analysis of the data was performed using SPSS software version 27, and appropriate tests (ANOVA and Kruskal-Wallis) were used for comparison of the data. Additionally, the results were presented graphically using Microsoft Excel version 2022.
Results
In this study, 60 Caspian Sea whitefish (Rutilus frisii) were randomly sampled from three coastal stations: Kiashahr, Bandar Anzali, and Bandar Astara (20 fish from each station) to investigate microplastic contamination. The gastrointestinal content analysis revealed the presence of microplastics in all samples.
The analysis of microplastic contamination in Caspian Sea whitefish showed that all 60 fish contained microplastics. The Anzali station, with an average of 53.75 ± 35.50 microplastic particles per fish, exhibited the highest microplastic abundance. One-way analysis of variance (ANOVA) indicated that the contamination levels at Anzali station were significantly higher than those at Kiashahr and Astara stations (p< 0.05). However, no significant difference was observed between Kiashahr and Astara. The color diversity of microplastics in Caspian Sea whitefish showed that both Kiashahr and Anzali stations exhibited greater color variety compared to Astara, with blue being the predominant color. In contrast, the Astara station displayed a relative dominance of red-colored microplastics. This suggests that the distribution of microplastic colors may vary, with local factors influencing this distribution.
The microplastics extracted from the gastrointestinal tracts of the fish were classified into six size categories: 0.5–1 mm, 1–2 mm, 2–3 mm, 3–4 mm, 4–5 mm, and larger than 5 mm. In all three stations, particles in the 3–4 mm range were the most abundant. A total of 1998 microplastic pieces were extracted from the gastrointestinal tracts of the 60 fish examined. All microplastics extracted from the fish were identified as fiber type microplastics across all three stations. The microplastics extracted from the gastrointestinal tracts of the fish were analyzed using FTIR-ATR spectroscopy. Eight different polymers were identified, including polyester, polyethylene (PE), polypropylene (PP), nylon, cellophane, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS). Among these, polyethylene (PE) was the most dominant polymer, accounting for 35% of the microplastics found in the gastrointestinal tracts of fish.
Discussion and conclusion
The present study demonstrated that 100% of Caspian Sea whitefish were contaminated with microplastics, indicating widespread contamination in this ecosystem. This finding is consistent with results from similar studies worldwide that have reported microplastic contamination in fishes (Arias et al., 2019; Tanaka and Takada, 2016). The primary sources of this pollution include the discharge of industrial and domestic wastewater through rivers and the release of fishing gear (Zakeri et al., 2020). Additionally, the diet of the whitefish, which includes bivalves contaminated with microplastics, plays a significant role in the transfer of this contamination to the fish (Bagheri et al., 2020). All microplastics found in the gastrointestinal tract of the fish were of the fiber type, which has also been identified as the predominant type in similar global studies (Luo et al., 2019; Hamed et al., 2023). In this study, microplastics of blue, red, pink, white, and green colors were found in the gastrointestinal tract of Caspian Sea whitefish. Blue and red colors were identified as the predominant colors. This finding is consistent with the results of Zhang et al., (2020), where blue was reported as the dominant color of microplastics. The size of the microplastics ranged from 0.5 mm to larger than 5 mm, with 3–4 mm being the predominant size. Various studies have reported different results; for instance, Tibbetts et al., (2018) reported microplastics smaller than 1 mm, and Zhao et al., (2015) reported sizes ranging from 1–2 mm. Smaller microplastics pose greater threats to marine organisms due to their larger surface area, higher chemical adsorption capacity, and greater potential for bioaccumulation (Van Cauwenberghe et al., 2015). These findings highlight the potential impacts of microplastics on the Caspian Sea ecosystem (Lu et al., 2016). In this study, polyethylene was identified as the most dominant polymer (35%) among the microplastics detected in the gastrointestinal tract of Caspian whitefish, a finding that aligns with previous research (Napper and Thompson, 2016; Li et al., 2020). The results of this study indicate that urban and industrial wastewater, fishing activities, tourism, and coastal erosion significantly contribute to the increase of microplastic contamination in the Caspian Sea. The accumulation of these particles in the whitefish can transfer contaminants to higher trophic levels in the food chain, posing a serious threat to human health. Therefore, effective plastic waste management and the implementation of stringent regulations to reduce pollution are essential.
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| Keywords: Caspian Sea, Rutilus kutum, Pollution, Microplastic. |
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Full-Text [PDF 777 kb]
(117 Downloads)
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Type of Study: Research |
Subject:
اكولوژي محيطهاي آبي
Received: 2024/09/19 | Accepted: 2024/12/30 | Published: 2025/03/1
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Haji Aghaei Ghazi Mahalleh F, Imanpour Namin J. Microplastic contamination in the whitefish (Rutilus frisii) from the southwestern Coasts of the Caspian Sea (Guilan Province). isfj 2024; 33 (5) :55-68 URL: http://isfj.ir/article-1-2831-en.html
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