Inha University Confirms Increase in Microplastic Accumulation Along the Tidal Flat Food Chain

Analysis of 19 Species from Muuido and Jawoldo Tidal Flats
Higher Microplastic Accumulation Found in Predators Than Prey

The research team from the Laboratory of Marine Animal Science in the Department of Marine Science and the Department of Biomedical Science and Engineering at Inha University has, for the first time in the world, confirmed that the accumulation of microplastics in tidal flat ecosystems increases along the food chain.

According to Inha University on August 18, the research team collected 81 samples—including seawater, sediment, seaweed, and benthic organisms—from the tidal flats of Muuido and Jawoldo in Ongjin County, Incheon, to analyze microplastic contamination. Benthic organisms refer to creatures that live on the tidal flat floor.

The analysis detected a total of 1,630 microplastic particles across all samples, with the highest number found in biological samples (1,428 particles), followed by sediment (110 particles) and seawater (92 particles). The main materials were polypropylene (PP), polyethylene (PE), and polystyrene (PS), with 65% of the particles ranging in size from 20 to 100 micrometers (μm).

Among predators such as the blue crab and Japanese swimming crab, an average of 3.63 microplastics per gram of wet weight (the weight of the organism with water content intact) was detected, which is more than four times higher than the 0.87 particles found in filter feeders, the main prey species such as clams and surf clams.

However, the study found that in some filter feeders, microplastics made of potentially hazardous materials such as polyvinyl chloride (PVC), polyacrylonitrile (PAN), and epoxy resin were detected. Thus, even if the number of microplastics detected is lower, it does not necessarily mean that the ecological risk is low.

Among detritivores—organisms like shrimp or gobies that consume organic matter around seaweed—an average of 26.69 microplastics per gram was detected, more than twice the average found in seaweed (11.62 particles per gram). Deposit feeders such as mudflat snails or sand crabs, which ingest sediment directly, also accumulated over six times more microplastics than filter feeders that filter particles from the water column.

The movement and accumulation pathway of microplastics in the tidal flat ecosystem, from seawater to sediment, seaweed, benthic organisms, and predators (numbers inside the arrows indicate bio-concentration, accumulation, and magnification factors). Provided by Inha University

The researchers analyzed that microplastics accumulate not just in seawater but also on the surfaces of sediments and seaweed, and that these particles can be transferred to higher trophic levels through feeding activities. The biomagnification factor calculated based on particle count between predators and their prey ranged from 3.9 to 9.6. The biomagnification factor indicates how much more a specific substance accumulates in the bodies of predators compared to their prey.

These findings were recently published in the 60th-anniversary special issue of the international academic journal in environmental science, Environmental Science & Technology.

The research team plans to continue examining the impact of microplastics on tidal flat ecosystems and seafood safety by conducting further analyses on microplastics’ mass, volume, chemical hazards, and actual food web structures.

Tae Won Kim, Professor at the Department of Marine Science at Inha University, stated, “This study is the first to confirm the phenomenon of microplastic accumulation and biomagnification along the food chain in the tidal flat ecosystem, where a much wider variety of species live, as previously observed in deep-sea hydrothermal vent ecosystems. By jointly analyzing the materials and sizes of microplastics with the feeding ecology of organisms, we can accurately assess the impact of microplastics on tidal flat ecosystems and seafood.”

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