Key Takeaways & Executive Findings
- •• • Gastrointestinal tracts of wild fish in Baiyangdian Lake contained the highest microplastic load at 11.63 ± 10.76 items/individual, exceeding gill (7.44 ± 6.79) and muscle (3.91 ± 3.16) counts, indicating ingestion as the primary exposure route and posing a risk of trophic transfer. • • Total microplastic abundance per fish ranged from 5 to 87 items, with a mean of 25.285 items; carnivorous and herbivorous species (e.g., snakehead and grass carp) exhibited significantly higher burdens than omnivorous and planktivorous species, demonstrating feeding habit as a key determinant of accumulation. • • Over 90% of detected microplastics were fibers smaller than 1 mm, with dominant polymers being chlorinated polyethylene (CPE), polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE), indicating sources from packaging and textile degradation. • • When normalized to body weight, smaller fish (mosquitofish and topmouth gudgeon) had higher microplastic concentrations in the gastrointestinal tract than larger fish, suggesting that lighter organisms face greater per-gram exposure and may serve as sensitive indicators of microplastic pollution.
Abstract
Microplastic pollution in freshwater environments has escalated, leading to increased accumulation in wild fish. This study investigated the occurrence characteristics of microplastics (MPs) in the gills, gastrointestinal tract (GIT), and muscle of four wild fish species with different feeding habits from Baiyangdian Lake, China. MPs were detected in all tissues. The average abundance was highest in the GIT (11.63 ± 10.76 items/individual), followed by gills (7.44 ± 6.79 items/individual), and lowest in muscle (3.91 ± 3.16 items/individual). The majority of MPs were transparent and black fibers smaller than 0.5 mm. Polymer analysis identified polypropylene (PP) and polyethylene (PE) as dominant components. Significant differences in MP abundance were observed among species, with carnivorous and herbivorous fish (e.g., snakehead and grass carp) showing higher total MPs than omnivorous and planktivorous fish (e.g., mosquitofish and topmouth gudgeon). However, when normalized by body weight, smaller fish exhibited higher MP concentrations in the GIT, suggesting a greater risk per unit mass. This study provides baseline data on tissue-specific MP distribution in wild freshwater fish with varying feeding behaviors and habitats, highlighting the influence of trophic level and body size on MP accumulation.
1. Introduction
Microplastic pollution in freshwater ecosystems has emerged as a critical environmental concern, with documented contamination in lakes worldwide. Baiyangdian Lake, the largest freshwater lake in the North China Plain, supports diverse aquatic life and significant fisheries, yet faces mounting pressures from industrial and urban development. While prior studies have confirmed microplastic presence in the lake's water and biota, systematic assessments linking fish feeding ecology to microplastic accumulation have been lacking. Existing commercial monitoring approaches often rely on single-species or single-tissue analyses, failing to capture the differential exposure pathways across trophic levels and habitat niches.
This study addresses that gap by analyzing microplastic burdens in gills, gastrointestinal tracts, and muscle tissues of four fish species with distinct feeding habits—herbivorous, omnivorous, planktivorous, and carnivorous—collected from Baiyangdian Lake. By quantifying abundance, size, shape, color, and polymer composition, we provide a comprehensive baseline that reveals how feeding behavior and body size influence microplastic uptake and tissue distribution. These findings are essential for refining risk assessments and developing targeted mitigation strategies for freshwater fisheries, particularly in regions where fish are a primary protein source for human populations.
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WANG Bingshuai, WANG Wei, MENG Xin, QI Jie (2026). Accumulation and Occurrence of Microplastics in Different Feeding Species of Wild Fish in Baiyangdian Lake. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025021005
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Frequently Asked Questions
What are the dominant polymer types found in fish tissues, and what do they indicate about pollution sources?
The dominant polymers were chlorinated polyethylene (CPE), polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE). CPE and PET are commonly used in packaging and textiles, while PP and PE are ubiquitous in consumer plastics. Their prevalence suggests inputs from urban runoff, wastewater effluent, and fishing gear degradation.
How does fish feeding habit influence microplastic accumulation, and which species are most at risk?
Carnivorous and herbivorous species (snakehead and grass carp) exhibited significantly higher total microplastic burdens (up to 87 items/individual) compared to omnivorous and planktivorous species (mosquitofish and topmouth gudgeon). This is likely due to trophic transfer in carnivores and accidental ingestion of contaminated vegetation in herbivores. However, when normalized by body weight, smaller fish had higher concentrations, indicating a greater per-gram risk.
What is the size distribution of microplastics in fish, and why is it important?
The majority of microplastics were smaller than 1 mm, with a significant proportion below 0.5 mm. Smaller particles are more easily ingested and can translocate across biological membranes, potentially causing greater physiological harm. The observed inverse relationship between particle size and abundance suggests that fragmentation processes are active in the environment.
Can microplastics be detected in fish muscle, and what are the implications for human consumption?
Yes, microplastics were detected in muscle tissue at an average abundance of 3.91 ± 3.16 items/individual. Although lower than in gills and gastrointestinal tract, their presence in edible muscle raises concerns about direct human exposure through fish consumption. The small size (<0.5 mm) of these particles may facilitate their accumulation in tissues.
How do microplastic abundances in Baiyangdian fish compare to other freshwater systems, and what are the ecological implications?
The average total abundance of 25.285 items/individual is within the range reported for other Chinese lakes (e.g., Taihu) but higher than some global freshwater systems. The significant interspecies variability underscores the importance of considering ecological traits in risk assessments. The higher per-gram burden in smaller fish suggests that juvenile or small-bodied species may be more vulnerable, potentially impacting population dynamics and food web integrity.
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