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Size matters more than shape: Ingestion of primary and secondary microplastics by small predators
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Researchers offered irregularly shaped secondary microplastics — fragments more realistic than the perfect spheres used in most lab studies — to small fish and shrimp at natural concentrations, finding that particle size was a stronger predictor of ingestion than shape. The study underscores that lab results using uniform plastic beads may overestimate real-world microplastic uptake in marine food webs.
Experimental studies have shown how microplastics are taken up by various aquatic organisms. Most of these studies have been carried out with small (<100 μm) symmetrically shaped primary microplastics (beads) which are not readily found in marine environment, and also in unnaturally high microplastic concentrations. We conducted experiments to study the ingestion of microplastics in more natural settings. We offered secondary microplastics to common planktivores, fish and mysid shrimps in their prey size categories to observe the uptake of such asymmetrically shaped fragments (PET > 200 μm and ABS > 100 μm) in comparison to primary microplastic beads (90 μm). Our results show that fragments of secondary plastics may end up in the food web but only in small amounts, and that the size of the fragments more than their shape is a crucial nominator influencing the numbers of plastics ingested. Future research aiming to resolve the effects of microplastics in the ecosystems should focus on environmentally relevant plastics and concentrations.
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Size- and shape-dependent ingestion and acute toxicity of fragmented and spherical microplastics in the absence and presence of prey on two marine zooplankton
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Researchers tested how the size and shape of microplastics affect their toxicity to tiny marine animals called zooplankton. Smaller particles were swallowed more often, but irregularly shaped fragments were more toxic than smooth spheres of similar size. When natural food was present, the animals ate fewer microplastics, suggesting that real-world toxicity depends on both particle characteristics and environmental conditions.
How Relevant Is the Accumulated Research on Commercial Spherical Nano- and Microplastics?
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A critical review asked how relevant research using commercial spherical plastic beads (a common lab standard) is to the irregularly shaped microplastics found in real environments. The analysis finds significant mismatches between lab model particles and environmental microplastics, urging more ecologically realistic experimental designs.
How size-dependent settling can both bias and inform microplastics observations
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Scientists studying how microplastics move and settle in water found that a particle's shape and size matter far more than the math formulas used to predict its movement — and shape/size data is often missing from real-world studies. This matters because tiny and large plastic particles sink or float at very different rates, which means water samples may be over- or under-counting certain particle sizes, making it harder to accurately assess how much microplastic — and what sizes — people and marine life are actually exposed to.
Interplay of Morphology and Polymer Composition Drives Estuarine Fate and Food Web Distribution of Nanoplastics: Evidence from a Multitrophic Mesocosm Using Upconversion Nanoparticle Tracers
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Scientists tested how two shapes of nanoplastics, tiny spheres versus tiny fibers, move through an estuary ecosystem, and found that fiber-shaped plastic sinks fast and builds up in fish liver tissue, while round particles cycle through the water and settle more evenly across shellfish and plants. This matters because most safety studies use round plastic beads as stand-ins, but this research suggests fibers (a very common form of real-world plastic pollution) may pose a bigger risk to fish, and potentially the people who eat them, than current testing methods capture.
Characterizing the multidimensionality of microplastics across environmental compartments
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Researchers characterized the size, shape, polymer type, volume, and mass of over 60,000 individual microplastic particles collected from various aquatic environments including surface water, sediments, and organisms. They found that particle size distributions follow predictable mathematical patterns that differ by environmental compartment and polymer type. The findings provide a framework for more realistic risk assessments by capturing the full diversity of microplastic characteristics relevant to toxicology.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.