Transfer of Microplastics through the Food Chain: A Silent Trophic Cascade

The accumulation of land-based debris washed into aquatic environments adds to the growing list of pollution sources; plastics—particularly microplastics—have evolved from being merely passive pollutants into active particulate entities that interact complexly with marine biogeochemical systems. Particles no larger than 5 mm originate from the degradation of macro-waste and primary products such as microbeads, and are now widely distributed from the water column to deep-sea sediments. The presence of microplastics is not only ubiquitous but also bioavailable, enabling direct interaction with marine organisms through ingestion, respiration, and even adsorption onto biological tissues.

The ocean, as a layered system, comprises various trophic levels ranging from primary producers such as phytoplankton, primary consumers such as zooplankton, to top predators such as fish and marine mammals. Energy and material transfer within the trophic levels was previously assumed to be limited to nutrients and organic biomass. However, the emergence of microplastics introduces a new dimension: the transfer of non-biological particulates that can follow the food chain, a phenomenon known as trophic transfer.

Microplastic Transfer in the Food Chain 

Secondary ingestion is the primary mechanism of microplastic transfer in the food chain, whereby predators consume prey that has been contaminated with microplastics. For example, this occurs in mussels (Mytilus edulis) exposed to polystyrene microspheres that are then fed to crabs (Carcinus maenas), resulting in the detection of microplastic particles in the hemolymph and various tissues of the predators. This confirms that microplastics not only persist in the digestive system but are also capable of translocating into internal tissues.

Furthermore, this phenomenon demonstrates that microplastics behave differently from classical chemical contaminants. Rather than undergoing diffusion or solubility-based bioaccumulation, microplastics move as discrete particles through cellular processes such as phagocytosis or endocytosis. Interestingly and often overlooked is that trophic transfer does not always result in linear biomagnification. Several studies indicate that microplastics can be eliminated through depuration processes over time, as evidenced by a significant reduction in particles within the crab’s body after 21 days. This suggests that biological systems possess a certain capacity to “clear” microplastics, although this process is not entirely efficient.

Microplastics and Their Effects on Organisms and Humans

The impacts of microplastics on marine organisms can be classified into physical and biological effects. Physically, microplastic particles can cause gastrointestinal obstruction, tissue irritation, and reduced feeding efficiency. In filter-feeding organisms such as bivalves, microplastics can replace natural food particles, thereby reducing energy intake and disrupting metabolic balance.

Biologically, the impacts are more subtle yet dangerous, stemming from microplastics’ ability to act as vectors for other contaminants such as heavy metals and persistent organic compounds. Furthermore, the presence of microplastics in internal tissues like the hepatopancreas and gonads indicates the potential for disruption of physiological and reproductive functions in organisms. The implications for humans become increasingly relevant when contaminated marine organisms are consumed. Microplastics have been detected in various seafood, thereby creating a direct exposure pathway for humans. Although the long-term effects are still under investigation, the potential for inflammation, oxidative stress, and the transfer of toxic chemicals presents a serious issue in marine food safety.

Avoiding the Adverse Effects of Microorganisms

The phenomenon of microplastic trophic transfer challenges the classical paradigm in ecotoxicology, which has traditionally focused on dissolved chemical compounds. Microplastics represent a new form of contamination that does not fully adhere to conventional bioaccumulation laws. They are dynamic, capable of moving and being eliminated, yet also have the potential to persist in certain tissues. Consequently, a concentration-based risk approach alone is insufficient to understand their ecological implications.

This issue is not merely a matter of pollution but a disruption to the “trophic architecture” of marine ecosystems. Microplastics do not merely enter the food chain; they interfere with the energy transfer process itself. This raises the possibility that, in the long term, trophic efficiency could be disrupted, with implications for ecosystem stability.

Moving forward, a multidisciplinary approach combining oceanography, ecotoxicology, and materials science is needed to comprehensively understand microplastic behavior. Furthermore, mitigation strategies must not focus solely on cleanup but must systematically target the sources of plastic production. Without intervention at the source, the trophic transfer of microplastics will continue to be an “invisible current” flowing through the web of marine life—and ultimately, back to humanity itself.

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Writer: Naisylla Nurmayanti